October 2019 - Linux-stable-mirror

FAILED: patch "[PATCH] KVM: PPC: Book3S HV: XIVE: Ensure VP isn't already in use" failed to apply to 4.14-stable tree

by gregkh＠linuxfoundation.org

The patch below does not apply to the 4.14-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable(a)vger.kernel.org>. thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From 12ade69c1eb9958b13374edf5ef742ea20ccffde Mon Sep 17 00:00:00 2001 From: Greg Kurz <groug(a)kaod.org> Date: Fri, 27 Sep 2019 13:53:43 +0200 Subject: [PATCH] KVM: PPC: Book3S HV: XIVE: Ensure VP isn't already in use MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Connecting a vCPU to a XIVE KVM device means establishing a 1:1 association between a vCPU id and the offset (VP id) of a VP structure within a fixed size block of VPs. We currently try to enforce the 1:1 relationship by checking that a vCPU with the same id isn't already connected. This is good but unfortunately not enough because we don't map VP ids to raw vCPU ids but to packed vCPU ids, and the packing function kvmppc_pack_vcpu_id() isn't bijective by design. We got away with it because QEMU passes vCPU ids that fit well in the packing pattern. But nothing prevents userspace to come up with a forged vCPU id resulting in a packed id collision which causes the KVM device to associate two vCPUs to the same VP. This greatly confuses the irq layer and ultimately crashes the kernel, as shown below. Example: a guest with 1 guest thread per core, a core stride of 8 and 300 vCPUs has vCPU ids 0,8,16...2392. If QEMU is patched to inject at some point an invalid vCPU id 348, which is the packed version of itself and 2392, we get: genirq: Flags mismatch irq 199. 00010000 (kvm-2-2392) vs. 00010000 (kvm-2-348) CPU: 24 PID: 88176 Comm: qemu-system-ppc Not tainted 5.3.0-xive-nr-servers-5.3-gku+ #38 Call Trace: [c000003f7f9937e0] [c000000000c0110c] dump_stack+0xb0/0xf4 (unreliable) [c000003f7f993820] [c0000000001cb480] __setup_irq+0xa70/0xad0 [c000003f7f9938d0] [c0000000001cb75c] request_threaded_irq+0x13c/0x260 [c000003f7f993940] [c00800000d44e7ac] kvmppc_xive_attach_escalation+0x104/0x270 [kvm] [c000003f7f9939d0] [c00800000d45013c] kvmppc_xive_connect_vcpu+0x424/0x620 [kvm] [c000003f7f993ac0] [c00800000d444428] kvm_arch_vcpu_ioctl+0x260/0x448 [kvm] [c000003f7f993b90] [c00800000d43593c] kvm_vcpu_ioctl+0x154/0x7c8 [kvm] [c000003f7f993d00] [c0000000004840f0] do_vfs_ioctl+0xe0/0xc30 [c000003f7f993db0] [c000000000484d44] ksys_ioctl+0x104/0x120 [c000003f7f993e00] [c000000000484d88] sys_ioctl+0x28/0x80 [c000003f7f993e20] [c00000000000b278] system_call+0x5c/0x68 xive-kvm: Failed to request escalation interrupt for queue 0 of VCPU 2392 ------------[ cut here ]------------ remove_proc_entry: removing non-empty directory 'irq/199', leaking at least 'kvm-2-348' WARNING: CPU: 24 PID: 88176 at /home/greg/Work/linux/kernel-kvm-ppc/fs/proc/generic.c:684 remove_proc_entry+0x1ec/0x200 Modules linked in: kvm_hv kvm dm_mod vhost_net vhost tap xt_CHECKSUM iptable_mangle xt_MASQUERADE iptable_nat nf_nat xt_conntrack nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 ipt_REJECT nf_reject_ipv4 tun bridge stp llc ebtable_filter ebtables ip6table_filter ip6_tables iptable_filter squashfs loop fuse i2c_dev sg ofpart ocxl powernv_flash at24 xts mtd uio_pdrv_genirq vmx_crypto opal_prd ipmi_powernv uio ipmi_devintf ipmi_msghandler ibmpowernv ib_iser rdma_cm iw_cm ib_cm ib_core iscsi_tcp libiscsi_tcp libiscsi scsi_transport_iscsi ip_tables ext4 mbcache jbd2 raid10 raid456 async_raid6_recov async_memcpy async_pq async_xor xor async_tx raid6_pq libcrc32c raid1 raid0 linear sd_mod ast i2c_algo_bit drm_vram_helper ttm drm_kms_helper syscopyarea sysfillrect sysimgblt fb_sys_fops drm ahci libahci libata tg3 drm_panel_orientation_quirks [last unloaded: kvm] CPU: 24 PID: 88176 Comm: qemu-system-ppc Not tainted 5.3.0-xive-nr-servers-5.3-gku+ #38 NIP: c00000000053b0cc LR: c00000000053b0c8 CTR: c0000000000ba3b0 REGS: c000003f7f9934b0 TRAP: 0700 Not tainted (5.3.0-xive-nr-servers-5.3-gku+) MSR: 9000000000029033 <SF,HV,EE,ME,IR,DR,RI,LE> CR: 48228222 XER: 20040000 CFAR: c000000000131a50 IRQMASK: 0 GPR00: c00000000053b0c8 c000003f7f993740 c0000000015ec500 0000000000000057 GPR04: 0000000000000001 0000000000000000 000049fb98484262 0000000000001bcf GPR08: 0000000000000007 0000000000000007 0000000000000001 9000000000001033 GPR12: 0000000000008000 c000003ffffeb800 0000000000000000 000000012f4ce5a1 GPR16: 000000012ef5a0c8 0000000000000000 000000012f113bb0 0000000000000000 GPR20: 000000012f45d918 c000003f863758b0 c000003f86375870 0000000000000006 GPR24: c000003f86375a30 0000000000000007 c0002039373d9020 c0000000014c4a48 GPR28: 0000000000000001 c000003fe62a4f6b c00020394b2e9fab c000003fe62a4ec0 NIP [c00000000053b0cc] remove_proc_entry+0x1ec/0x200 LR [c00000000053b0c8] remove_proc_entry+0x1e8/0x200 Call Trace: [c000003f7f993740] [c00000000053b0c8] remove_proc_entry+0x1e8/0x200 (unreliable) [c000003f7f9937e0] [c0000000001d3654] unregister_irq_proc+0x114/0x150 [c000003f7f993880] [c0000000001c6284] free_desc+0x54/0xb0 [c000003f7f9938c0] [c0000000001c65ec] irq_free_descs+0xac/0x100 [c000003f7f993910] [c0000000001d1ff8] irq_dispose_mapping+0x68/0x80 [c000003f7f993940] [c00800000d44e8a4] kvmppc_xive_attach_escalation+0x1fc/0x270 [kvm] [c000003f7f9939d0] [c00800000d45013c] kvmppc_xive_connect_vcpu+0x424/0x620 [kvm] [c000003f7f993ac0] [c00800000d444428] kvm_arch_vcpu_ioctl+0x260/0x448 [kvm] [c000003f7f993b90] [c00800000d43593c] kvm_vcpu_ioctl+0x154/0x7c8 [kvm] [c000003f7f993d00] [c0000000004840f0] do_vfs_ioctl+0xe0/0xc30 [c000003f7f993db0] [c000000000484d44] ksys_ioctl+0x104/0x120 [c000003f7f993e00] [c000000000484d88] sys_ioctl+0x28/0x80 [c000003f7f993e20] [c00000000000b278] system_call+0x5c/0x68 Instruction dump: 2c230000 41820008 3923ff78 e8e900a0 3c82ff69 3c62ff8d 7fa6eb78 7fc5f378 3884f080 3863b948 4bbf6925 60000000 <0fe00000> 4bffff7c fba10088 4bbf6e41 ---[ end trace b925b67a74a1d8d1 ]--- BUG: Kernel NULL pointer dereference at 0x00000010 Faulting instruction address: 0xc00800000d44fc04 Oops: Kernel access of bad area, sig: 11 [#1] LE PAGE_SIZE=64K MMU=Radix MMU=Hash SMP NR_CPUS=2048 NUMA PowerNV Modules linked in: kvm_hv kvm dm_mod vhost_net vhost tap xt_CHECKSUM iptable_mangle xt_MASQUERADE iptable_nat nf_nat xt_conntrack nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 ipt_REJECT nf_reject_ipv4 tun bridge stp llc ebtable_filter ebtables ip6table_filter ip6_tables iptable_filter squashfs loop fuse i2c_dev sg ofpart ocxl powernv_flash at24 xts mtd uio_pdrv_genirq vmx_crypto opal_prd ipmi_powernv uio ipmi_devintf ipmi_msghandler ibmpowernv ib_iser rdma_cm iw_cm ib_cm ib_core iscsi_tcp libiscsi_tcp libiscsi scsi_transport_iscsi ip_tables ext4 mbcache jbd2 raid10 raid456 async_raid6_recov async_memcpy async_pq async_xor xor async_tx raid6_pq libcrc32c raid1 raid0 linear sd_mod ast i2c_algo_bit drm_vram_helper ttm drm_kms_helper syscopyarea sysfillrect sysimgblt fb_sys_fops drm ahci libahci libata tg3 drm_panel_orientation_quirks [last unloaded: kvm] CPU: 24 PID: 88176 Comm: qemu-system-ppc Tainted: G W 5.3.0-xive-nr-servers-5.3-gku+ #38 NIP: c00800000d44fc04 LR: c00800000d44fc00 CTR: c0000000001cd970 REGS: c000003f7f9938e0 TRAP: 0300 Tainted: G W (5.3.0-xive-nr-servers-5.3-gku+) MSR: 9000000000009033 <SF,HV,EE,ME,IR,DR,RI,LE> CR: 24228882 XER: 20040000 CFAR: c0000000001cd9ac DAR: 0000000000000010 DSISR: 40000000 IRQMASK: 0 GPR00: c00800000d44fc00 c000003f7f993b70 c00800000d468300 0000000000000000 GPR04: 00000000000000c7 0000000000000000 0000000000000000 c000003ffacd06d8 GPR08: 0000000000000000 c000003ffacd0738 0000000000000000 fffffffffffffffd GPR12: 0000000000000040 c000003ffffeb800 0000000000000000 000000012f4ce5a1 GPR16: 000000012ef5a0c8 0000000000000000 000000012f113bb0 0000000000000000 GPR20: 000000012f45d918 00007ffffe0d9a80 000000012f4f5df0 000000012ef8c9f8 GPR24: 0000000000000001 0000000000000000 c000003fe4501ed0 c000003f8b1d0000 GPR28: c0000033314689c0 c000003fe4501c00 c000003fe4501e70 c000003fe4501e90 NIP [c00800000d44fc04] kvmppc_xive_cleanup_vcpu+0xfc/0x210 [kvm] LR [c00800000d44fc00] kvmppc_xive_cleanup_vcpu+0xf8/0x210 [kvm] Call Trace: [c000003f7f993b70] [c00800000d44fc00] kvmppc_xive_cleanup_vcpu+0xf8/0x210 [kvm] (unreliable) [c000003f7f993bd0] [c00800000d450bd4] kvmppc_xive_release+0xdc/0x1b0 [kvm] [c000003f7f993c30] [c00800000d436a98] kvm_device_release+0xb0/0x110 [kvm] [c000003f7f993c70] [c00000000046730c] __fput+0xec/0x320 [c000003f7f993cd0] [c000000000164ae0] task_work_run+0x150/0x1c0 [c000003f7f993d30] [c000000000025034] do_notify_resume+0x304/0x440 [c000003f7f993e20] [c00000000000dcc4] ret_from_except_lite+0x70/0x74 Instruction dump: 3bff0008 7fbfd040 419e0054 847e0004 2fa30000 419effec e93d0000 8929203c 2f890000 419effb8 4800821d e8410018 <e9230010> e9490008 9b2a0039 7c0004ac ---[ end trace b925b67a74a1d8d2 ]--- Kernel panic - not syncing: Fatal exception This affects both XIVE and XICS-on-XIVE devices since the beginning. Check the VP id instead of the vCPU id when a new vCPU is connected. The allocation of the XIVE CPU structure in kvmppc_xive_connect_vcpu() is moved after the check to avoid the need for rollback. Cc: stable(a)vger.kernel.org # v4.12+ Signed-off-by: Greg Kurz <groug(a)kaod.org> Reviewed-by: Cédric Le Goater <clg(a)kaod.org> Signed-off-by: Paul Mackerras <paulus(a)ozlabs.org> diff --git a/arch/powerpc/kvm/book3s_xive.c b/arch/powerpc/kvm/book3s_xive.c index 591bfb4bfd0f..a3f9c665bb5b 100644 --- a/arch/powerpc/kvm/book3s_xive.c +++ b/arch/powerpc/kvm/book3s_xive.c @@ -1217,6 +1217,7 @@ int kvmppc_xive_connect_vcpu(struct kvm_device *dev, struct kvmppc_xive *xive = dev->private; struct kvmppc_xive_vcpu *xc; int i, r = -EBUSY; + u32 vp_id; pr_devel("connect_vcpu(cpu=%d)\n", cpu); @@ -1228,25 +1229,32 @@ int kvmppc_xive_connect_vcpu(struct kvm_device *dev, return -EPERM; if (vcpu->arch.irq_type != KVMPPC_IRQ_DEFAULT) return -EBUSY; - if (kvmppc_xive_find_server(vcpu->kvm, cpu)) { - pr_devel("Duplicate !\n"); - return -EEXIST; - } if (cpu >= (KVM_MAX_VCPUS * vcpu->kvm->arch.emul_smt_mode)) { pr_devel("Out of bounds !\n"); return -EINVAL; } - xc = kzalloc(sizeof(*xc), GFP_KERNEL); - if (!xc) - return -ENOMEM; /* We need to synchronize with queue provisioning */ mutex_lock(&xive->lock); + + vp_id = kvmppc_xive_vp(xive, cpu); + if (kvmppc_xive_vp_in_use(xive->kvm, vp_id)) { + pr_devel("Duplicate !\n"); + r = -EEXIST; + goto bail; + } + + xc = kzalloc(sizeof(*xc), GFP_KERNEL); + if (!xc) { + r = -ENOMEM; + goto bail; + } + vcpu->arch.xive_vcpu = xc; xc->xive = xive; xc->vcpu = vcpu; xc->server_num = cpu; - xc->vp_id = kvmppc_xive_vp(xive, cpu); + xc->vp_id = vp_id; xc->mfrr = 0xff; xc->valid = true; diff --git a/arch/powerpc/kvm/book3s_xive.h b/arch/powerpc/kvm/book3s_xive.h index 955b820ffd6d..fe3ed50e0818 100644 --- a/arch/powerpc/kvm/book3s_xive.h +++ b/arch/powerpc/kvm/book3s_xive.h @@ -220,6 +220,18 @@ static inline u32 kvmppc_xive_vp(struct kvmppc_xive *xive, u32 server) return xive->vp_base + kvmppc_pack_vcpu_id(xive->kvm, server); } +static inline bool kvmppc_xive_vp_in_use(struct kvm *kvm, u32 vp_id) +{ + struct kvm_vcpu *vcpu = NULL; + int i; + + kvm_for_each_vcpu(i, vcpu, kvm) { + if (vcpu->arch.xive_vcpu && vp_id == vcpu->arch.xive_vcpu->vp_id) + return true; + } + return false; +} + /* * Mapping between guest priorities and host priorities * is as follow. diff --git a/arch/powerpc/kvm/book3s_xive_native.c b/arch/powerpc/kvm/book3s_xive_native.c index 248c1ea9e788..78b906ffa0d2 100644 --- a/arch/powerpc/kvm/book3s_xive_native.c +++ b/arch/powerpc/kvm/book3s_xive_native.c @@ -106,6 +106,7 @@ int kvmppc_xive_native_connect_vcpu(struct kvm_device *dev, struct kvmppc_xive *xive = dev->private; struct kvmppc_xive_vcpu *xc = NULL; int rc; + u32 vp_id; pr_devel("native_connect_vcpu(server=%d)\n", server_num); @@ -124,7 +125,8 @@ int kvmppc_xive_native_connect_vcpu(struct kvm_device *dev, mutex_lock(&xive->lock); - if (kvmppc_xive_find_server(vcpu->kvm, server_num)) { + vp_id = kvmppc_xive_vp(xive, server_num); + if (kvmppc_xive_vp_in_use(xive->kvm, vp_id)) { pr_devel("Duplicate !\n"); rc = -EEXIST; goto bail; @@ -141,7 +143,7 @@ int kvmppc_xive_native_connect_vcpu(struct kvm_device *dev, xc->vcpu = vcpu; xc->server_num = server_num; - xc->vp_id = kvmppc_xive_vp(xive, server_num); + xc->vp_id = vp_id; xc->valid = true; vcpu->arch.irq_type = KVMPPC_IRQ_XIVE;

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FAILED: patch "[PATCH] KVM: PPC: Book3S HV: XIVE: Ensure VP isn't already in use" failed to apply to 4.19-stable tree

by gregkh＠linuxfoundation.org

The patch below does not apply to the 4.19-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable(a)vger.kernel.org>. thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From 12ade69c1eb9958b13374edf5ef742ea20ccffde Mon Sep 17 00:00:00 2001 From: Greg Kurz <groug(a)kaod.org> Date: Fri, 27 Sep 2019 13:53:43 +0200 Subject: [PATCH] KVM: PPC: Book3S HV: XIVE: Ensure VP isn't already in use MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Connecting a vCPU to a XIVE KVM device means establishing a 1:1 association between a vCPU id and the offset (VP id) of a VP structure within a fixed size block of VPs. We currently try to enforce the 1:1 relationship by checking that a vCPU with the same id isn't already connected. This is good but unfortunately not enough because we don't map VP ids to raw vCPU ids but to packed vCPU ids, and the packing function kvmppc_pack_vcpu_id() isn't bijective by design. We got away with it because QEMU passes vCPU ids that fit well in the packing pattern. But nothing prevents userspace to come up with a forged vCPU id resulting in a packed id collision which causes the KVM device to associate two vCPUs to the same VP. This greatly confuses the irq layer and ultimately crashes the kernel, as shown below. Example: a guest with 1 guest thread per core, a core stride of 8 and 300 vCPUs has vCPU ids 0,8,16...2392. If QEMU is patched to inject at some point an invalid vCPU id 348, which is the packed version of itself and 2392, we get: genirq: Flags mismatch irq 199. 00010000 (kvm-2-2392) vs. 00010000 (kvm-2-348) CPU: 24 PID: 88176 Comm: qemu-system-ppc Not tainted 5.3.0-xive-nr-servers-5.3-gku+ #38 Call Trace: [c000003f7f9937e0] [c000000000c0110c] dump_stack+0xb0/0xf4 (unreliable) [c000003f7f993820] [c0000000001cb480] __setup_irq+0xa70/0xad0 [c000003f7f9938d0] [c0000000001cb75c] request_threaded_irq+0x13c/0x260 [c000003f7f993940] [c00800000d44e7ac] kvmppc_xive_attach_escalation+0x104/0x270 [kvm] [c000003f7f9939d0] [c00800000d45013c] kvmppc_xive_connect_vcpu+0x424/0x620 [kvm] [c000003f7f993ac0] [c00800000d444428] kvm_arch_vcpu_ioctl+0x260/0x448 [kvm] [c000003f7f993b90] [c00800000d43593c] kvm_vcpu_ioctl+0x154/0x7c8 [kvm] [c000003f7f993d00] [c0000000004840f0] do_vfs_ioctl+0xe0/0xc30 [c000003f7f993db0] [c000000000484d44] ksys_ioctl+0x104/0x120 [c000003f7f993e00] [c000000000484d88] sys_ioctl+0x28/0x80 [c000003f7f993e20] [c00000000000b278] system_call+0x5c/0x68 xive-kvm: Failed to request escalation interrupt for queue 0 of VCPU 2392 ------------[ cut here ]------------ remove_proc_entry: removing non-empty directory 'irq/199', leaking at least 'kvm-2-348' WARNING: CPU: 24 PID: 88176 at /home/greg/Work/linux/kernel-kvm-ppc/fs/proc/generic.c:684 remove_proc_entry+0x1ec/0x200 Modules linked in: kvm_hv kvm dm_mod vhost_net vhost tap xt_CHECKSUM iptable_mangle xt_MASQUERADE iptable_nat nf_nat xt_conntrack nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 ipt_REJECT nf_reject_ipv4 tun bridge stp llc ebtable_filter ebtables ip6table_filter ip6_tables iptable_filter squashfs loop fuse i2c_dev sg ofpart ocxl powernv_flash at24 xts mtd uio_pdrv_genirq vmx_crypto opal_prd ipmi_powernv uio ipmi_devintf ipmi_msghandler ibmpowernv ib_iser rdma_cm iw_cm ib_cm ib_core iscsi_tcp libiscsi_tcp libiscsi scsi_transport_iscsi ip_tables ext4 mbcache jbd2 raid10 raid456 async_raid6_recov async_memcpy async_pq async_xor xor async_tx raid6_pq libcrc32c raid1 raid0 linear sd_mod ast i2c_algo_bit drm_vram_helper ttm drm_kms_helper syscopyarea sysfillrect sysimgblt fb_sys_fops drm ahci libahci libata tg3 drm_panel_orientation_quirks [last unloaded: kvm] CPU: 24 PID: 88176 Comm: qemu-system-ppc Not tainted 5.3.0-xive-nr-servers-5.3-gku+ #38 NIP: c00000000053b0cc LR: c00000000053b0c8 CTR: c0000000000ba3b0 REGS: c000003f7f9934b0 TRAP: 0700 Not tainted (5.3.0-xive-nr-servers-5.3-gku+) MSR: 9000000000029033 <SF,HV,EE,ME,IR,DR,RI,LE> CR: 48228222 XER: 20040000 CFAR: c000000000131a50 IRQMASK: 0 GPR00: c00000000053b0c8 c000003f7f993740 c0000000015ec500 0000000000000057 GPR04: 0000000000000001 0000000000000000 000049fb98484262 0000000000001bcf GPR08: 0000000000000007 0000000000000007 0000000000000001 9000000000001033 GPR12: 0000000000008000 c000003ffffeb800 0000000000000000 000000012f4ce5a1 GPR16: 000000012ef5a0c8 0000000000000000 000000012f113bb0 0000000000000000 GPR20: 000000012f45d918 c000003f863758b0 c000003f86375870 0000000000000006 GPR24: c000003f86375a30 0000000000000007 c0002039373d9020 c0000000014c4a48 GPR28: 0000000000000001 c000003fe62a4f6b c00020394b2e9fab c000003fe62a4ec0 NIP [c00000000053b0cc] remove_proc_entry+0x1ec/0x200 LR [c00000000053b0c8] remove_proc_entry+0x1e8/0x200 Call Trace: [c000003f7f993740] [c00000000053b0c8] remove_proc_entry+0x1e8/0x200 (unreliable) [c000003f7f9937e0] [c0000000001d3654] unregister_irq_proc+0x114/0x150 [c000003f7f993880] [c0000000001c6284] free_desc+0x54/0xb0 [c000003f7f9938c0] [c0000000001c65ec] irq_free_descs+0xac/0x100 [c000003f7f993910] [c0000000001d1ff8] irq_dispose_mapping+0x68/0x80 [c000003f7f993940] [c00800000d44e8a4] kvmppc_xive_attach_escalation+0x1fc/0x270 [kvm] [c000003f7f9939d0] [c00800000d45013c] kvmppc_xive_connect_vcpu+0x424/0x620 [kvm] [c000003f7f993ac0] [c00800000d444428] kvm_arch_vcpu_ioctl+0x260/0x448 [kvm] [c000003f7f993b90] [c00800000d43593c] kvm_vcpu_ioctl+0x154/0x7c8 [kvm] [c000003f7f993d00] [c0000000004840f0] do_vfs_ioctl+0xe0/0xc30 [c000003f7f993db0] [c000000000484d44] ksys_ioctl+0x104/0x120 [c000003f7f993e00] [c000000000484d88] sys_ioctl+0x28/0x80 [c000003f7f993e20] [c00000000000b278] system_call+0x5c/0x68 Instruction dump: 2c230000 41820008 3923ff78 e8e900a0 3c82ff69 3c62ff8d 7fa6eb78 7fc5f378 3884f080 3863b948 4bbf6925 60000000 <0fe00000> 4bffff7c fba10088 4bbf6e41 ---[ end trace b925b67a74a1d8d1 ]--- BUG: Kernel NULL pointer dereference at 0x00000010 Faulting instruction address: 0xc00800000d44fc04 Oops: Kernel access of bad area, sig: 11 [#1] LE PAGE_SIZE=64K MMU=Radix MMU=Hash SMP NR_CPUS=2048 NUMA PowerNV Modules linked in: kvm_hv kvm dm_mod vhost_net vhost tap xt_CHECKSUM iptable_mangle xt_MASQUERADE iptable_nat nf_nat xt_conntrack nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 ipt_REJECT nf_reject_ipv4 tun bridge stp llc ebtable_filter ebtables ip6table_filter ip6_tables iptable_filter squashfs loop fuse i2c_dev sg ofpart ocxl powernv_flash at24 xts mtd uio_pdrv_genirq vmx_crypto opal_prd ipmi_powernv uio ipmi_devintf ipmi_msghandler ibmpowernv ib_iser rdma_cm iw_cm ib_cm ib_core iscsi_tcp libiscsi_tcp libiscsi scsi_transport_iscsi ip_tables ext4 mbcache jbd2 raid10 raid456 async_raid6_recov async_memcpy async_pq async_xor xor async_tx raid6_pq libcrc32c raid1 raid0 linear sd_mod ast i2c_algo_bit drm_vram_helper ttm drm_kms_helper syscopyarea sysfillrect sysimgblt fb_sys_fops drm ahci libahci libata tg3 drm_panel_orientation_quirks [last unloaded: kvm] CPU: 24 PID: 88176 Comm: qemu-system-ppc Tainted: G W 5.3.0-xive-nr-servers-5.3-gku+ #38 NIP: c00800000d44fc04 LR: c00800000d44fc00 CTR: c0000000001cd970 REGS: c000003f7f9938e0 TRAP: 0300 Tainted: G W (5.3.0-xive-nr-servers-5.3-gku+) MSR: 9000000000009033 <SF,HV,EE,ME,IR,DR,RI,LE> CR: 24228882 XER: 20040000 CFAR: c0000000001cd9ac DAR: 0000000000000010 DSISR: 40000000 IRQMASK: 0 GPR00: c00800000d44fc00 c000003f7f993b70 c00800000d468300 0000000000000000 GPR04: 00000000000000c7 0000000000000000 0000000000000000 c000003ffacd06d8 GPR08: 0000000000000000 c000003ffacd0738 0000000000000000 fffffffffffffffd GPR12: 0000000000000040 c000003ffffeb800 0000000000000000 000000012f4ce5a1 GPR16: 000000012ef5a0c8 0000000000000000 000000012f113bb0 0000000000000000 GPR20: 000000012f45d918 00007ffffe0d9a80 000000012f4f5df0 000000012ef8c9f8 GPR24: 0000000000000001 0000000000000000 c000003fe4501ed0 c000003f8b1d0000 GPR28: c0000033314689c0 c000003fe4501c00 c000003fe4501e70 c000003fe4501e90 NIP [c00800000d44fc04] kvmppc_xive_cleanup_vcpu+0xfc/0x210 [kvm] LR [c00800000d44fc00] kvmppc_xive_cleanup_vcpu+0xf8/0x210 [kvm] Call Trace: [c000003f7f993b70] [c00800000d44fc00] kvmppc_xive_cleanup_vcpu+0xf8/0x210 [kvm] (unreliable) [c000003f7f993bd0] [c00800000d450bd4] kvmppc_xive_release+0xdc/0x1b0 [kvm] [c000003f7f993c30] [c00800000d436a98] kvm_device_release+0xb0/0x110 [kvm] [c000003f7f993c70] [c00000000046730c] __fput+0xec/0x320 [c000003f7f993cd0] [c000000000164ae0] task_work_run+0x150/0x1c0 [c000003f7f993d30] [c000000000025034] do_notify_resume+0x304/0x440 [c000003f7f993e20] [c00000000000dcc4] ret_from_except_lite+0x70/0x74 Instruction dump: 3bff0008 7fbfd040 419e0054 847e0004 2fa30000 419effec e93d0000 8929203c 2f890000 419effb8 4800821d e8410018 <e9230010> e9490008 9b2a0039 7c0004ac ---[ end trace b925b67a74a1d8d2 ]--- Kernel panic - not syncing: Fatal exception This affects both XIVE and XICS-on-XIVE devices since the beginning. Check the VP id instead of the vCPU id when a new vCPU is connected. The allocation of the XIVE CPU structure in kvmppc_xive_connect_vcpu() is moved after the check to avoid the need for rollback. Cc: stable(a)vger.kernel.org # v4.12+ Signed-off-by: Greg Kurz <groug(a)kaod.org> Reviewed-by: Cédric Le Goater <clg(a)kaod.org> Signed-off-by: Paul Mackerras <paulus(a)ozlabs.org> diff --git a/arch/powerpc/kvm/book3s_xive.c b/arch/powerpc/kvm/book3s_xive.c index 591bfb4bfd0f..a3f9c665bb5b 100644 --- a/arch/powerpc/kvm/book3s_xive.c +++ b/arch/powerpc/kvm/book3s_xive.c @@ -1217,6 +1217,7 @@ int kvmppc_xive_connect_vcpu(struct kvm_device *dev, struct kvmppc_xive *xive = dev->private; struct kvmppc_xive_vcpu *xc; int i, r = -EBUSY; + u32 vp_id; pr_devel("connect_vcpu(cpu=%d)\n", cpu); @@ -1228,25 +1229,32 @@ int kvmppc_xive_connect_vcpu(struct kvm_device *dev, return -EPERM; if (vcpu->arch.irq_type != KVMPPC_IRQ_DEFAULT) return -EBUSY; - if (kvmppc_xive_find_server(vcpu->kvm, cpu)) { - pr_devel("Duplicate !\n"); - return -EEXIST; - } if (cpu >= (KVM_MAX_VCPUS * vcpu->kvm->arch.emul_smt_mode)) { pr_devel("Out of bounds !\n"); return -EINVAL; } - xc = kzalloc(sizeof(*xc), GFP_KERNEL); - if (!xc) - return -ENOMEM; /* We need to synchronize with queue provisioning */ mutex_lock(&xive->lock); + + vp_id = kvmppc_xive_vp(xive, cpu); + if (kvmppc_xive_vp_in_use(xive->kvm, vp_id)) { + pr_devel("Duplicate !\n"); + r = -EEXIST; + goto bail; + } + + xc = kzalloc(sizeof(*xc), GFP_KERNEL); + if (!xc) { + r = -ENOMEM; + goto bail; + } + vcpu->arch.xive_vcpu = xc; xc->xive = xive; xc->vcpu = vcpu; xc->server_num = cpu; - xc->vp_id = kvmppc_xive_vp(xive, cpu); + xc->vp_id = vp_id; xc->mfrr = 0xff; xc->valid = true; diff --git a/arch/powerpc/kvm/book3s_xive.h b/arch/powerpc/kvm/book3s_xive.h index 955b820ffd6d..fe3ed50e0818 100644 --- a/arch/powerpc/kvm/book3s_xive.h +++ b/arch/powerpc/kvm/book3s_xive.h @@ -220,6 +220,18 @@ static inline u32 kvmppc_xive_vp(struct kvmppc_xive *xive, u32 server) return xive->vp_base + kvmppc_pack_vcpu_id(xive->kvm, server); } +static inline bool kvmppc_xive_vp_in_use(struct kvm *kvm, u32 vp_id) +{ + struct kvm_vcpu *vcpu = NULL; + int i; + + kvm_for_each_vcpu(i, vcpu, kvm) { + if (vcpu->arch.xive_vcpu && vp_id == vcpu->arch.xive_vcpu->vp_id) + return true; + } + return false; +} + /* * Mapping between guest priorities and host priorities * is as follow. diff --git a/arch/powerpc/kvm/book3s_xive_native.c b/arch/powerpc/kvm/book3s_xive_native.c index 248c1ea9e788..78b906ffa0d2 100644 --- a/arch/powerpc/kvm/book3s_xive_native.c +++ b/arch/powerpc/kvm/book3s_xive_native.c @@ -106,6 +106,7 @@ int kvmppc_xive_native_connect_vcpu(struct kvm_device *dev, struct kvmppc_xive *xive = dev->private; struct kvmppc_xive_vcpu *xc = NULL; int rc; + u32 vp_id; pr_devel("native_connect_vcpu(server=%d)\n", server_num); @@ -124,7 +125,8 @@ int kvmppc_xive_native_connect_vcpu(struct kvm_device *dev, mutex_lock(&xive->lock); - if (kvmppc_xive_find_server(vcpu->kvm, server_num)) { + vp_id = kvmppc_xive_vp(xive, server_num); + if (kvmppc_xive_vp_in_use(xive->kvm, vp_id)) { pr_devel("Duplicate !\n"); rc = -EEXIST; goto bail; @@ -141,7 +143,7 @@ int kvmppc_xive_native_connect_vcpu(struct kvm_device *dev, xc->vcpu = vcpu; xc->server_num = server_num; - xc->vp_id = kvmppc_xive_vp(xive, server_num); + xc->vp_id = vp_id; xc->valid = true; vcpu->arch.irq_type = KVMPPC_IRQ_XIVE;

5 years, 2 months

1
0
0 0

FAILED: patch "[PATCH] btrfs: qgroup: Always free PREALLOC META reserve in" failed to apply to 4.19-stable tree

by gregkh＠linuxfoundation.org

The patch below does not apply to the 4.19-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable(a)vger.kernel.org>. thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From 8702ba9396bf7bbae2ab93c94acd4bd37cfa4f09 Mon Sep 17 00:00:00 2001 From: Qu Wenruo <wqu(a)suse.com> Date: Mon, 14 Oct 2019 14:34:51 +0800 Subject: [PATCH] btrfs: qgroup: Always free PREALLOC META reserve in btrfs_delalloc_release_extents() [Background] Btrfs qgroup uses two types of reserved space for METADATA space, PERTRANS and PREALLOC. PERTRANS is metadata space reserved for each transaction started by btrfs_start_transaction(). While PREALLOC is for delalloc, where we reserve space before joining a transaction, and finally it will be converted to PERTRANS after the writeback is done. [Inconsistency] However there is inconsistency in how we handle PREALLOC metadata space. The most obvious one is: In btrfs_buffered_write(): btrfs_delalloc_release_extents(BTRFS_I(inode), reserve_bytes, true); We always free qgroup PREALLOC meta space. While in btrfs_truncate_block(): btrfs_delalloc_release_extents(BTRFS_I(inode), blocksize, (ret != 0)); We only free qgroup PREALLOC meta space when something went wrong. [The Correct Behavior] The correct behavior should be the one in btrfs_buffered_write(), we should always free PREALLOC metadata space. The reason is, the btrfs_delalloc_* mechanism works by: - Reserve metadata first, even it's not necessary In btrfs_delalloc_reserve_metadata() - Free the unused metadata space Normally in: btrfs_delalloc_release_extents() |- btrfs_inode_rsv_release() Here we do calculation on whether we should release or not. E.g. for 64K buffered write, the metadata rsv works like: /* The first page */ reserve_meta: num_bytes=calc_inode_reservations() free_meta: num_bytes=0 total: num_bytes=calc_inode_reservations() /* The first page caused one outstanding extent, thus needs metadata rsv */ /* The 2nd page */ reserve_meta: num_bytes=calc_inode_reservations() free_meta: num_bytes=calc_inode_reservations() total: not changed /* The 2nd page doesn't cause new outstanding extent, needs no new meta rsv, so we free what we have reserved */ /* The 3rd~16th pages */ reserve_meta: num_bytes=calc_inode_reservations() free_meta: num_bytes=calc_inode_reservations() total: not changed (still space for one outstanding extent) This means, if btrfs_delalloc_release_extents() determines to free some space, then those space should be freed NOW. So for qgroup, we should call btrfs_qgroup_free_meta_prealloc() other than btrfs_qgroup_convert_reserved_meta(). The good news is: - The callers are not that hot The hottest caller is in btrfs_buffered_write(), which is already fixed by commit 336a8bb8e36a ("btrfs: Fix wrong btrfs_delalloc_release_extents parameter"). Thus it's not that easy to cause false EDQUOT. - The trans commit in advance for qgroup would hide the bug Since commit f5fef4593653 ("btrfs: qgroup: Make qgroup async transaction commit more aggressive"), when btrfs qgroup metadata free space is slow, it will try to commit transaction and free the wrongly converted PERTRANS space, so it's not that easy to hit such bug. [FIX] So to fix the problem, remove the @qgroup_free parameter for btrfs_delalloc_release_extents(), and always pass true to btrfs_inode_rsv_release(). Reported-by: Filipe Manana <fdmanana(a)suse.com> Fixes: 43b18595d660 ("btrfs: qgroup: Use separate meta reservation type for delalloc") CC: stable(a)vger.kernel.org # 4.19+ Reviewed-by: Filipe Manana <fdmanana(a)suse.com> Signed-off-by: Qu Wenruo <wqu(a)suse.com> Signed-off-by: David Sterba <dsterba(a)suse.com> diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h index c1489c229694..fe2b8765d9e6 100644 --- a/fs/btrfs/ctree.h +++ b/fs/btrfs/ctree.h @@ -2487,8 +2487,7 @@ int btrfs_subvolume_reserve_metadata(struct btrfs_root *root, int nitems, bool use_global_rsv); void btrfs_subvolume_release_metadata(struct btrfs_fs_info *fs_info, struct btrfs_block_rsv *rsv); -void btrfs_delalloc_release_extents(struct btrfs_inode *inode, u64 num_bytes, - bool qgroup_free); +void btrfs_delalloc_release_extents(struct btrfs_inode *inode, u64 num_bytes); int btrfs_delalloc_reserve_metadata(struct btrfs_inode *inode, u64 num_bytes); u64 btrfs_account_ro_block_groups_free_space(struct btrfs_space_info *sinfo); diff --git a/fs/btrfs/delalloc-space.c b/fs/btrfs/delalloc-space.c index d949d7d2abed..571e7b31ea2f 100644 --- a/fs/btrfs/delalloc-space.c +++ b/fs/btrfs/delalloc-space.c @@ -418,7 +418,6 @@ void btrfs_delalloc_release_metadata(struct btrfs_inode *inode, u64 num_bytes, * btrfs_delalloc_release_extents - release our outstanding_extents * @inode: the inode to balance the reservation for. * @num_bytes: the number of bytes we originally reserved with - * @qgroup_free: do we need to free qgroup meta reservation or convert them. * * When we reserve space we increase outstanding_extents for the extents we may * add. Once we've set the range as delalloc or created our ordered extents we @@ -426,8 +425,7 @@ void btrfs_delalloc_release_metadata(struct btrfs_inode *inode, u64 num_bytes, * temporarily tracked outstanding_extents. This _must_ be used in conjunction * with btrfs_delalloc_reserve_metadata. */ -void btrfs_delalloc_release_extents(struct btrfs_inode *inode, u64 num_bytes, - bool qgroup_free) +void btrfs_delalloc_release_extents(struct btrfs_inode *inode, u64 num_bytes) { struct btrfs_fs_info *fs_info = inode->root->fs_info; unsigned num_extents; @@ -441,7 +439,7 @@ void btrfs_delalloc_release_extents(struct btrfs_inode *inode, u64 num_bytes, if (btrfs_is_testing(fs_info)) return; - btrfs_inode_rsv_release(inode, qgroup_free); + btrfs_inode_rsv_release(inode, true); } /** diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c index 27e5b269e729..e955e7fa9201 100644 --- a/fs/btrfs/file.c +++ b/fs/btrfs/file.c @@ -1692,7 +1692,7 @@ static noinline ssize_t btrfs_buffered_write(struct kiocb *iocb, force_page_uptodate); if (ret) { btrfs_delalloc_release_extents(BTRFS_I(inode), - reserve_bytes, true); + reserve_bytes); break; } @@ -1704,7 +1704,7 @@ static noinline ssize_t btrfs_buffered_write(struct kiocb *iocb, if (extents_locked == -EAGAIN) goto again; btrfs_delalloc_release_extents(BTRFS_I(inode), - reserve_bytes, true); + reserve_bytes); ret = extents_locked; break; } @@ -1772,8 +1772,7 @@ static noinline ssize_t btrfs_buffered_write(struct kiocb *iocb, else free_extent_state(cached_state); - btrfs_delalloc_release_extents(BTRFS_I(inode), reserve_bytes, - true); + btrfs_delalloc_release_extents(BTRFS_I(inode), reserve_bytes); if (ret) { btrfs_drop_pages(pages, num_pages); break; diff --git a/fs/btrfs/inode-map.c b/fs/btrfs/inode-map.c index 63cad7865d75..37345fb6191d 100644 --- a/fs/btrfs/inode-map.c +++ b/fs/btrfs/inode-map.c @@ -501,13 +501,13 @@ int btrfs_save_ino_cache(struct btrfs_root *root, ret = btrfs_prealloc_file_range_trans(inode, trans, 0, 0, prealloc, prealloc, prealloc, &alloc_hint); if (ret) { - btrfs_delalloc_release_extents(BTRFS_I(inode), prealloc, true); + btrfs_delalloc_release_extents(BTRFS_I(inode), prealloc); btrfs_delalloc_release_metadata(BTRFS_I(inode), prealloc, true); goto out_put; } ret = btrfs_write_out_ino_cache(root, trans, path, inode); - btrfs_delalloc_release_extents(BTRFS_I(inode), prealloc, false); + btrfs_delalloc_release_extents(BTRFS_I(inode), prealloc); out_put: iput(inode); out_release: diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c index 0f2754eaa05b..c3f386b7cc0b 100644 --- a/fs/btrfs/inode.c +++ b/fs/btrfs/inode.c @@ -2206,7 +2206,7 @@ static void btrfs_writepage_fixup_worker(struct btrfs_work *work) ClearPageChecked(page); set_page_dirty(page); - btrfs_delalloc_release_extents(BTRFS_I(inode), PAGE_SIZE, false); + btrfs_delalloc_release_extents(BTRFS_I(inode), PAGE_SIZE); out: unlock_extent_cached(&BTRFS_I(inode)->io_tree, page_start, page_end, &cached_state); @@ -4951,7 +4951,7 @@ int btrfs_truncate_block(struct inode *inode, loff_t from, loff_t len, if (!page) { btrfs_delalloc_release_space(inode, data_reserved, block_start, blocksize, true); - btrfs_delalloc_release_extents(BTRFS_I(inode), blocksize, true); + btrfs_delalloc_release_extents(BTRFS_I(inode), blocksize); ret = -ENOMEM; goto out; } @@ -5018,7 +5018,7 @@ int btrfs_truncate_block(struct inode *inode, loff_t from, loff_t len, if (ret) btrfs_delalloc_release_space(inode, data_reserved, block_start, blocksize, true); - btrfs_delalloc_release_extents(BTRFS_I(inode), blocksize, (ret != 0)); + btrfs_delalloc_release_extents(BTRFS_I(inode), blocksize); unlock_page(page); put_page(page); out: @@ -8709,7 +8709,7 @@ static ssize_t btrfs_direct_IO(struct kiocb *iocb, struct iov_iter *iter) } else if (ret >= 0 && (size_t)ret < count) btrfs_delalloc_release_space(inode, data_reserved, offset, count - (size_t)ret, true); - btrfs_delalloc_release_extents(BTRFS_I(inode), count, false); + btrfs_delalloc_release_extents(BTRFS_I(inode), count); } out: if (wakeup) @@ -9059,7 +9059,7 @@ vm_fault_t btrfs_page_mkwrite(struct vm_fault *vmf) unlock_extent_cached(io_tree, page_start, page_end, &cached_state); if (!ret2) { - btrfs_delalloc_release_extents(BTRFS_I(inode), PAGE_SIZE, true); + btrfs_delalloc_release_extents(BTRFS_I(inode), PAGE_SIZE); sb_end_pagefault(inode->i_sb); extent_changeset_free(data_reserved); return VM_FAULT_LOCKED; @@ -9068,7 +9068,7 @@ vm_fault_t btrfs_page_mkwrite(struct vm_fault *vmf) out_unlock: unlock_page(page); out: - btrfs_delalloc_release_extents(BTRFS_I(inode), PAGE_SIZE, (ret != 0)); + btrfs_delalloc_release_extents(BTRFS_I(inode), PAGE_SIZE); btrfs_delalloc_release_space(inode, data_reserved, page_start, reserved_space, (ret != 0)); out_noreserve: diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c index de730e56d3f5..7c145a41decd 100644 --- a/fs/btrfs/ioctl.c +++ b/fs/btrfs/ioctl.c @@ -1360,8 +1360,7 @@ static int cluster_pages_for_defrag(struct inode *inode, unlock_page(pages[i]); put_page(pages[i]); } - btrfs_delalloc_release_extents(BTRFS_I(inode), page_cnt << PAGE_SHIFT, - false); + btrfs_delalloc_release_extents(BTRFS_I(inode), page_cnt << PAGE_SHIFT); extent_changeset_free(data_reserved); return i_done; out: @@ -1372,8 +1371,7 @@ static int cluster_pages_for_defrag(struct inode *inode, btrfs_delalloc_release_space(inode, data_reserved, start_index << PAGE_SHIFT, page_cnt << PAGE_SHIFT, true); - btrfs_delalloc_release_extents(BTRFS_I(inode), page_cnt << PAGE_SHIFT, - true); + btrfs_delalloc_release_extents(BTRFS_I(inode), page_cnt << PAGE_SHIFT); extent_changeset_free(data_reserved); return ret; diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c index 7b883239fa7e..5cd42b66818c 100644 --- a/fs/btrfs/relocation.c +++ b/fs/btrfs/relocation.c @@ -3278,7 +3278,7 @@ static int relocate_file_extent_cluster(struct inode *inode, btrfs_delalloc_release_metadata(BTRFS_I(inode), PAGE_SIZE, true); btrfs_delalloc_release_extents(BTRFS_I(inode), - PAGE_SIZE, true); + PAGE_SIZE); ret = -ENOMEM; goto out; } @@ -3299,7 +3299,7 @@ static int relocate_file_extent_cluster(struct inode *inode, btrfs_delalloc_release_metadata(BTRFS_I(inode), PAGE_SIZE, true); btrfs_delalloc_release_extents(BTRFS_I(inode), - PAGE_SIZE, true); + PAGE_SIZE); ret = -EIO; goto out; } @@ -3328,7 +3328,7 @@ static int relocate_file_extent_cluster(struct inode *inode, btrfs_delalloc_release_metadata(BTRFS_I(inode), PAGE_SIZE, true); btrfs_delalloc_release_extents(BTRFS_I(inode), - PAGE_SIZE, true); + PAGE_SIZE); clear_extent_bits(&BTRFS_I(inode)->io_tree, page_start, page_end, @@ -3344,8 +3344,7 @@ static int relocate_file_extent_cluster(struct inode *inode, put_page(page); index++; - btrfs_delalloc_release_extents(BTRFS_I(inode), PAGE_SIZE, - false); + btrfs_delalloc_release_extents(BTRFS_I(inode), PAGE_SIZE); balance_dirty_pages_ratelimited(inode->i_mapping); btrfs_throttle(fs_info); }

5 years, 2 months

1
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FAILED: patch "[PATCH] Btrfs: check for the full sync flag while holding the inode" failed to apply to 4.4-stable tree

by gregkh＠linuxfoundation.org

The patch below does not apply to the 4.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable(a)vger.kernel.org>. thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From ba0b084ac309283db6e329785c1dc4f45fdbd379 Mon Sep 17 00:00:00 2001 From: Filipe Manana <fdmanana(a)suse.com> Date: Wed, 16 Oct 2019 16:28:52 +0100 Subject: [PATCH] Btrfs: check for the full sync flag while holding the inode lock during fsync We were checking for the full fsync flag in the inode before locking the inode, which is racy, since at that that time it might not be set but after we acquire the inode lock some other task set it. One case where this can happen is on a system low on memory and some concurrent task failed to allocate an extent map and therefore set the full sync flag on the inode, to force the next fsync to work in full mode. A consequence of missing the full fsync flag set is hitting the problems fixed by commit 0c713cbab620 ("Btrfs: fix race between ranged fsync and writeback of adjacent ranges"), BUG_ON() when dropping extents from a log tree, hitting assertion failures at tree-log.c:copy_items() or all sorts of weird inconsistencies after replaying a log due to file extents items representing ranges that overlap. So just move the check such that it's done after locking the inode and before starting writeback again. Fixes: 0c713cbab620 ("Btrfs: fix race between ranged fsync and writeback of adjacent ranges") CC: stable(a)vger.kernel.org # 5.2+ Signed-off-by: Filipe Manana <fdmanana(a)suse.com> Signed-off-by: David Sterba <dsterba(a)suse.com> diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c index e955e7fa9201..435a502a3226 100644 --- a/fs/btrfs/file.c +++ b/fs/btrfs/file.c @@ -2067,25 +2067,7 @@ int btrfs_sync_file(struct file *file, loff_t start, loff_t end, int datasync) struct btrfs_trans_handle *trans; struct btrfs_log_ctx ctx; int ret = 0, err; - u64 len; - /* - * If the inode needs a full sync, make sure we use a full range to - * avoid log tree corruption, due to hole detection racing with ordered - * extent completion for adjacent ranges, and assertion failures during - * hole detection. - */ - if (test_bit(BTRFS_INODE_NEEDS_FULL_SYNC, - &BTRFS_I(inode)->runtime_flags)) { - start = 0; - end = LLONG_MAX; - } - - /* - * The range length can be represented by u64, we have to do the typecasts - * to avoid signed overflow if it's [0, LLONG_MAX] eg. from fsync() - */ - len = (u64)end - (u64)start + 1; trace_btrfs_sync_file(file, datasync); btrfs_init_log_ctx(&ctx, inode); @@ -2111,6 +2093,19 @@ int btrfs_sync_file(struct file *file, loff_t start, loff_t end, int datasync) atomic_inc(&root->log_batch); + /* + * If the inode needs a full sync, make sure we use a full range to + * avoid log tree corruption, due to hole detection racing with ordered + * extent completion for adjacent ranges, and assertion failures during + * hole detection. Do this while holding the inode lock, to avoid races + * with other tasks. + */ + if (test_bit(BTRFS_INODE_NEEDS_FULL_SYNC, + &BTRFS_I(inode)->runtime_flags)) { + start = 0; + end = LLONG_MAX; + } + /* * Before we acquired the inode's lock, someone may have dirtied more * pages in the target range. We need to make sure that writeback for @@ -2138,8 +2133,11 @@ int btrfs_sync_file(struct file *file, loff_t start, loff_t end, int datasync) /* * We have to do this here to avoid the priority inversion of waiting on * IO of a lower priority task while holding a transaction open. + * + * Also, the range length can be represented by u64, we have to do the + * typecasts to avoid signed overflow if it's [0, LLONG_MAX]. */ - ret = btrfs_wait_ordered_range(inode, start, len); + ret = btrfs_wait_ordered_range(inode, start, (u64)end - (u64)start + 1); if (ret) { up_write(&BTRFS_I(inode)->dio_sem); inode_unlock(inode);

5 years, 2 months

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FAILED: patch "[PATCH] Btrfs: check for the full sync flag while holding the inode" failed to apply to 4.9-stable tree

by gregkh＠linuxfoundation.org

The patch below does not apply to the 4.9-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable(a)vger.kernel.org>. thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From ba0b084ac309283db6e329785c1dc4f45fdbd379 Mon Sep 17 00:00:00 2001 From: Filipe Manana <fdmanana(a)suse.com> Date: Wed, 16 Oct 2019 16:28:52 +0100 Subject: [PATCH] Btrfs: check for the full sync flag while holding the inode lock during fsync We were checking for the full fsync flag in the inode before locking the inode, which is racy, since at that that time it might not be set but after we acquire the inode lock some other task set it. One case where this can happen is on a system low on memory and some concurrent task failed to allocate an extent map and therefore set the full sync flag on the inode, to force the next fsync to work in full mode. A consequence of missing the full fsync flag set is hitting the problems fixed by commit 0c713cbab620 ("Btrfs: fix race between ranged fsync and writeback of adjacent ranges"), BUG_ON() when dropping extents from a log tree, hitting assertion failures at tree-log.c:copy_items() or all sorts of weird inconsistencies after replaying a log due to file extents items representing ranges that overlap. So just move the check such that it's done after locking the inode and before starting writeback again. Fixes: 0c713cbab620 ("Btrfs: fix race between ranged fsync and writeback of adjacent ranges") CC: stable(a)vger.kernel.org # 5.2+ Signed-off-by: Filipe Manana <fdmanana(a)suse.com> Signed-off-by: David Sterba <dsterba(a)suse.com> diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c index e955e7fa9201..435a502a3226 100644 --- a/fs/btrfs/file.c +++ b/fs/btrfs/file.c @@ -2067,25 +2067,7 @@ int btrfs_sync_file(struct file *file, loff_t start, loff_t end, int datasync) struct btrfs_trans_handle *trans; struct btrfs_log_ctx ctx; int ret = 0, err; - u64 len; - /* - * If the inode needs a full sync, make sure we use a full range to - * avoid log tree corruption, due to hole detection racing with ordered - * extent completion for adjacent ranges, and assertion failures during - * hole detection. - */ - if (test_bit(BTRFS_INODE_NEEDS_FULL_SYNC, - &BTRFS_I(inode)->runtime_flags)) { - start = 0; - end = LLONG_MAX; - } - - /* - * The range length can be represented by u64, we have to do the typecasts - * to avoid signed overflow if it's [0, LLONG_MAX] eg. from fsync() - */ - len = (u64)end - (u64)start + 1; trace_btrfs_sync_file(file, datasync); btrfs_init_log_ctx(&ctx, inode); @@ -2111,6 +2093,19 @@ int btrfs_sync_file(struct file *file, loff_t start, loff_t end, int datasync) atomic_inc(&root->log_batch); + /* + * If the inode needs a full sync, make sure we use a full range to + * avoid log tree corruption, due to hole detection racing with ordered + * extent completion for adjacent ranges, and assertion failures during + * hole detection. Do this while holding the inode lock, to avoid races + * with other tasks. + */ + if (test_bit(BTRFS_INODE_NEEDS_FULL_SYNC, + &BTRFS_I(inode)->runtime_flags)) { + start = 0; + end = LLONG_MAX; + } + /* * Before we acquired the inode's lock, someone may have dirtied more * pages in the target range. We need to make sure that writeback for @@ -2138,8 +2133,11 @@ int btrfs_sync_file(struct file *file, loff_t start, loff_t end, int datasync) /* * We have to do this here to avoid the priority inversion of waiting on * IO of a lower priority task while holding a transaction open. + * + * Also, the range length can be represented by u64, we have to do the + * typecasts to avoid signed overflow if it's [0, LLONG_MAX]. */ - ret = btrfs_wait_ordered_range(inode, start, len); + ret = btrfs_wait_ordered_range(inode, start, (u64)end - (u64)start + 1); if (ret) { up_write(&BTRFS_I(inode)->dio_sem); inode_unlock(inode);

5 years, 2 months

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FAILED: patch "[PATCH] Btrfs: check for the full sync flag while holding the inode" failed to apply to 4.14-stable tree

by gregkh＠linuxfoundation.org

The patch below does not apply to the 4.14-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable(a)vger.kernel.org>. thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From ba0b084ac309283db6e329785c1dc4f45fdbd379 Mon Sep 17 00:00:00 2001 From: Filipe Manana <fdmanana(a)suse.com> Date: Wed, 16 Oct 2019 16:28:52 +0100 Subject: [PATCH] Btrfs: check for the full sync flag while holding the inode lock during fsync We were checking for the full fsync flag in the inode before locking the inode, which is racy, since at that that time it might not be set but after we acquire the inode lock some other task set it. One case where this can happen is on a system low on memory and some concurrent task failed to allocate an extent map and therefore set the full sync flag on the inode, to force the next fsync to work in full mode. A consequence of missing the full fsync flag set is hitting the problems fixed by commit 0c713cbab620 ("Btrfs: fix race between ranged fsync and writeback of adjacent ranges"), BUG_ON() when dropping extents from a log tree, hitting assertion failures at tree-log.c:copy_items() or all sorts of weird inconsistencies after replaying a log due to file extents items representing ranges that overlap. So just move the check such that it's done after locking the inode and before starting writeback again. Fixes: 0c713cbab620 ("Btrfs: fix race between ranged fsync and writeback of adjacent ranges") CC: stable(a)vger.kernel.org # 5.2+ Signed-off-by: Filipe Manana <fdmanana(a)suse.com> Signed-off-by: David Sterba <dsterba(a)suse.com> diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c index e955e7fa9201..435a502a3226 100644 --- a/fs/btrfs/file.c +++ b/fs/btrfs/file.c @@ -2067,25 +2067,7 @@ int btrfs_sync_file(struct file *file, loff_t start, loff_t end, int datasync) struct btrfs_trans_handle *trans; struct btrfs_log_ctx ctx; int ret = 0, err; - u64 len; - /* - * If the inode needs a full sync, make sure we use a full range to - * avoid log tree corruption, due to hole detection racing with ordered - * extent completion for adjacent ranges, and assertion failures during - * hole detection. - */ - if (test_bit(BTRFS_INODE_NEEDS_FULL_SYNC, - &BTRFS_I(inode)->runtime_flags)) { - start = 0; - end = LLONG_MAX; - } - - /* - * The range length can be represented by u64, we have to do the typecasts - * to avoid signed overflow if it's [0, LLONG_MAX] eg. from fsync() - */ - len = (u64)end - (u64)start + 1; trace_btrfs_sync_file(file, datasync); btrfs_init_log_ctx(&ctx, inode); @@ -2111,6 +2093,19 @@ int btrfs_sync_file(struct file *file, loff_t start, loff_t end, int datasync) atomic_inc(&root->log_batch); + /* + * If the inode needs a full sync, make sure we use a full range to + * avoid log tree corruption, due to hole detection racing with ordered + * extent completion for adjacent ranges, and assertion failures during + * hole detection. Do this while holding the inode lock, to avoid races + * with other tasks. + */ + if (test_bit(BTRFS_INODE_NEEDS_FULL_SYNC, + &BTRFS_I(inode)->runtime_flags)) { + start = 0; + end = LLONG_MAX; + } + /* * Before we acquired the inode's lock, someone may have dirtied more * pages in the target range. We need to make sure that writeback for @@ -2138,8 +2133,11 @@ int btrfs_sync_file(struct file *file, loff_t start, loff_t end, int datasync) /* * We have to do this here to avoid the priority inversion of waiting on * IO of a lower priority task while holding a transaction open. + * + * Also, the range length can be represented by u64, we have to do the + * typecasts to avoid signed overflow if it's [0, LLONG_MAX]. */ - ret = btrfs_wait_ordered_range(inode, start, len); + ret = btrfs_wait_ordered_range(inode, start, (u64)end - (u64)start + 1); if (ret) { up_write(&BTRFS_I(inode)->dio_sem); inode_unlock(inode);

5 years, 2 months

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FAILED: patch "[PATCH] dm snapshot: rework COW throttling to fix deadlock" failed to apply to 4.4-stable tree

by gregkh＠linuxfoundation.org

The patch below does not apply to the 4.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable(a)vger.kernel.org>. thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From b21555786f18cd77f2311ad89074533109ae3ffa Mon Sep 17 00:00:00 2001 From: Mikulas Patocka <mpatocka(a)redhat.com> Date: Wed, 2 Oct 2019 06:15:53 -0400 Subject: [PATCH] dm snapshot: rework COW throttling to fix deadlock Commit 721b1d98fb517a ("dm snapshot: Fix excessive memory usage and workqueue stalls") introduced a semaphore to limit the maximum number of in-flight kcopyd (COW) jobs. The implementation of this throttling mechanism is prone to a deadlock: 1. One or more threads write to the origin device causing COW, which is performed by kcopyd. 2. At some point some of these threads might reach the s->cow_count semaphore limit and block in down(&s->cow_count), holding a read lock on _origins_lock. 3. Someone tries to acquire a write lock on _origins_lock, e.g., snapshot_ctr(), which blocks because the threads at step (2) already hold a read lock on it. 4. A COW operation completes and kcopyd runs dm-snapshot's completion callback, which ends up calling pending_complete(). pending_complete() tries to resubmit any deferred origin bios. This requires acquiring a read lock on _origins_lock, which blocks. This happens because the read-write semaphore implementation gives priority to writers, meaning that as soon as a writer tries to enter the critical section, no readers will be allowed in, until all writers have completed their work. So, pending_complete() waits for the writer at step (3) to acquire and release the lock. This writer waits for the readers at step (2) to release the read lock and those readers wait for pending_complete() (the kcopyd thread) to signal the s->cow_count semaphore: DEADLOCK. The above was thoroughly analyzed and documented by Nikos Tsironis as part of his initial proposal for fixing this deadlock, see: https://www.redhat.com/archives/dm-devel/2019-October/msg00001.html Fix this deadlock by reworking COW throttling so that it waits without holding any locks. Add a variable 'in_progress' that counts how many kcopyd jobs are running. A function wait_for_in_progress() will sleep if 'in_progress' is over the limit. It drops _origins_lock in order to avoid the deadlock. Reported-by: Guruswamy Basavaiah <guru2018(a)gmail.com> Reported-by: Nikos Tsironis <ntsironis(a)arrikto.com> Reviewed-by: Nikos Tsironis <ntsironis(a)arrikto.com> Tested-by: Nikos Tsironis <ntsironis(a)arrikto.com> Fixes: 721b1d98fb51 ("dm snapshot: Fix excessive memory usage and workqueue stalls") Cc: stable(a)vger.kernel.org # v5.0+ Depends-on: 4a3f111a73a8c ("dm snapshot: introduce account_start_copy() and account_end_copy()") Signed-off-by: Mikulas Patocka <mpatocka(a)redhat.com> Signed-off-by: Mike Snitzer <snitzer(a)redhat.com> diff --git a/drivers/md/dm-snap.c b/drivers/md/dm-snap.c index da3bd1794ee0..4fb1a40e68a0 100644 --- a/drivers/md/dm-snap.c +++ b/drivers/md/dm-snap.c @@ -18,7 +18,6 @@ #include <linux/vmalloc.h> #include <linux/log2.h> #include <linux/dm-kcopyd.h> -#include <linux/semaphore.h> #include "dm.h" @@ -107,8 +106,8 @@ struct dm_snapshot { /* The on disk metadata handler */ struct dm_exception_store *store; - /* Maximum number of in-flight COW jobs. */ - struct semaphore cow_count; + unsigned in_progress; + struct wait_queue_head in_progress_wait; struct dm_kcopyd_client *kcopyd_client; @@ -162,8 +161,8 @@ struct dm_snapshot { */ #define DEFAULT_COW_THRESHOLD 2048 -static int cow_threshold = DEFAULT_COW_THRESHOLD; -module_param_named(snapshot_cow_threshold, cow_threshold, int, 0644); +static unsigned cow_threshold = DEFAULT_COW_THRESHOLD; +module_param_named(snapshot_cow_threshold, cow_threshold, uint, 0644); MODULE_PARM_DESC(snapshot_cow_threshold, "Maximum number of chunks being copied on write"); DECLARE_DM_KCOPYD_THROTTLE_WITH_MODULE_PARM(snapshot_copy_throttle, @@ -1327,7 +1326,7 @@ static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv) goto bad_hash_tables; } - sema_init(&s->cow_count, (cow_threshold > 0) ? cow_threshold : INT_MAX); + init_waitqueue_head(&s->in_progress_wait); s->kcopyd_client = dm_kcopyd_client_create(&dm_kcopyd_throttle); if (IS_ERR(s->kcopyd_client)) { @@ -1509,17 +1508,54 @@ static void snapshot_dtr(struct dm_target *ti) dm_put_device(ti, s->origin); + WARN_ON(s->in_progress); + kfree(s); } static void account_start_copy(struct dm_snapshot *s) { - down(&s->cow_count); + spin_lock(&s->in_progress_wait.lock); + s->in_progress++; + spin_unlock(&s->in_progress_wait.lock); } static void account_end_copy(struct dm_snapshot *s) { - up(&s->cow_count); + spin_lock(&s->in_progress_wait.lock); + BUG_ON(!s->in_progress); + s->in_progress--; + if (likely(s->in_progress <= cow_threshold) && + unlikely(waitqueue_active(&s->in_progress_wait))) + wake_up_locked(&s->in_progress_wait); + spin_unlock(&s->in_progress_wait.lock); +} + +static bool wait_for_in_progress(struct dm_snapshot *s, bool unlock_origins) +{ + if (unlikely(s->in_progress > cow_threshold)) { + spin_lock(&s->in_progress_wait.lock); + if (likely(s->in_progress > cow_threshold)) { + /* + * NOTE: this throttle doesn't account for whether + * the caller is servicing an IO that will trigger a COW + * so excess throttling may result for chunks not required + * to be COW'd. But if cow_threshold was reached, extra + * throttling is unlikely to negatively impact performance. + */ + DECLARE_WAITQUEUE(wait, current); + __add_wait_queue(&s->in_progress_wait, &wait); + __set_current_state(TASK_UNINTERRUPTIBLE); + spin_unlock(&s->in_progress_wait.lock); + if (unlock_origins) + up_read(&_origins_lock); + io_schedule(); + remove_wait_queue(&s->in_progress_wait, &wait); + return false; + } + spin_unlock(&s->in_progress_wait.lock); + } + return true; } /* @@ -1537,7 +1573,7 @@ static void flush_bios(struct bio *bio) } } -static int do_origin(struct dm_dev *origin, struct bio *bio); +static int do_origin(struct dm_dev *origin, struct bio *bio, bool limit); /* * Flush a list of buffers. @@ -1550,7 +1586,7 @@ static void retry_origin_bios(struct dm_snapshot *s, struct bio *bio) while (bio) { n = bio->bi_next; bio->bi_next = NULL; - r = do_origin(s->origin, bio); + r = do_origin(s->origin, bio, false); if (r == DM_MAPIO_REMAPPED) generic_make_request(bio); bio = n; @@ -1926,6 +1962,11 @@ static int snapshot_map(struct dm_target *ti, struct bio *bio) if (!s->valid) return DM_MAPIO_KILL; + if (bio_data_dir(bio) == WRITE) { + while (unlikely(!wait_for_in_progress(s, false))) + ; /* wait_for_in_progress() has slept */ + } + down_read(&s->lock); dm_exception_table_lock(&lock); @@ -2122,7 +2163,7 @@ static int snapshot_merge_map(struct dm_target *ti, struct bio *bio) if (bio_data_dir(bio) == WRITE) { up_write(&s->lock); - return do_origin(s->origin, bio); + return do_origin(s->origin, bio, false); } out_unlock: @@ -2497,15 +2538,24 @@ static int __origin_write(struct list_head *snapshots, sector_t sector, /* * Called on a write from the origin driver. */ -static int do_origin(struct dm_dev *origin, struct bio *bio) +static int do_origin(struct dm_dev *origin, struct bio *bio, bool limit) { struct origin *o; int r = DM_MAPIO_REMAPPED; +again: down_read(&_origins_lock); o = __lookup_origin(origin->bdev); - if (o) + if (o) { + if (limit) { + struct dm_snapshot *s; + list_for_each_entry(s, &o->snapshots, list) + if (unlikely(!wait_for_in_progress(s, true))) + goto again; + } + r = __origin_write(&o->snapshots, bio->bi_iter.bi_sector, bio); + } up_read(&_origins_lock); return r; @@ -2618,7 +2668,7 @@ static int origin_map(struct dm_target *ti, struct bio *bio) dm_accept_partial_bio(bio, available_sectors); /* Only tell snapshots if this is a write */ - return do_origin(o->dev, bio); + return do_origin(o->dev, bio, true); } /*

5 years, 2 months

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FAILED: patch "[PATCH] dm snapshot: rework COW throttling to fix deadlock" failed to apply to 4.9-stable tree

by gregkh＠linuxfoundation.org

The patch below does not apply to the 4.9-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable(a)vger.kernel.org>. thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From b21555786f18cd77f2311ad89074533109ae3ffa Mon Sep 17 00:00:00 2001 From: Mikulas Patocka <mpatocka(a)redhat.com> Date: Wed, 2 Oct 2019 06:15:53 -0400 Subject: [PATCH] dm snapshot: rework COW throttling to fix deadlock Commit 721b1d98fb517a ("dm snapshot: Fix excessive memory usage and workqueue stalls") introduced a semaphore to limit the maximum number of in-flight kcopyd (COW) jobs. The implementation of this throttling mechanism is prone to a deadlock: 1. One or more threads write to the origin device causing COW, which is performed by kcopyd. 2. At some point some of these threads might reach the s->cow_count semaphore limit and block in down(&s->cow_count), holding a read lock on _origins_lock. 3. Someone tries to acquire a write lock on _origins_lock, e.g., snapshot_ctr(), which blocks because the threads at step (2) already hold a read lock on it. 4. A COW operation completes and kcopyd runs dm-snapshot's completion callback, which ends up calling pending_complete(). pending_complete() tries to resubmit any deferred origin bios. This requires acquiring a read lock on _origins_lock, which blocks. This happens because the read-write semaphore implementation gives priority to writers, meaning that as soon as a writer tries to enter the critical section, no readers will be allowed in, until all writers have completed their work. So, pending_complete() waits for the writer at step (3) to acquire and release the lock. This writer waits for the readers at step (2) to release the read lock and those readers wait for pending_complete() (the kcopyd thread) to signal the s->cow_count semaphore: DEADLOCK. The above was thoroughly analyzed and documented by Nikos Tsironis as part of his initial proposal for fixing this deadlock, see: https://www.redhat.com/archives/dm-devel/2019-October/msg00001.html Fix this deadlock by reworking COW throttling so that it waits without holding any locks. Add a variable 'in_progress' that counts how many kcopyd jobs are running. A function wait_for_in_progress() will sleep if 'in_progress' is over the limit. It drops _origins_lock in order to avoid the deadlock. Reported-by: Guruswamy Basavaiah <guru2018(a)gmail.com> Reported-by: Nikos Tsironis <ntsironis(a)arrikto.com> Reviewed-by: Nikos Tsironis <ntsironis(a)arrikto.com> Tested-by: Nikos Tsironis <ntsironis(a)arrikto.com> Fixes: 721b1d98fb51 ("dm snapshot: Fix excessive memory usage and workqueue stalls") Cc: stable(a)vger.kernel.org # v5.0+ Depends-on: 4a3f111a73a8c ("dm snapshot: introduce account_start_copy() and account_end_copy()") Signed-off-by: Mikulas Patocka <mpatocka(a)redhat.com> Signed-off-by: Mike Snitzer <snitzer(a)redhat.com> diff --git a/drivers/md/dm-snap.c b/drivers/md/dm-snap.c index da3bd1794ee0..4fb1a40e68a0 100644 --- a/drivers/md/dm-snap.c +++ b/drivers/md/dm-snap.c @@ -18,7 +18,6 @@ #include <linux/vmalloc.h> #include <linux/log2.h> #include <linux/dm-kcopyd.h> -#include <linux/semaphore.h> #include "dm.h" @@ -107,8 +106,8 @@ struct dm_snapshot { /* The on disk metadata handler */ struct dm_exception_store *store; - /* Maximum number of in-flight COW jobs. */ - struct semaphore cow_count; + unsigned in_progress; + struct wait_queue_head in_progress_wait; struct dm_kcopyd_client *kcopyd_client; @@ -162,8 +161,8 @@ struct dm_snapshot { */ #define DEFAULT_COW_THRESHOLD 2048 -static int cow_threshold = DEFAULT_COW_THRESHOLD; -module_param_named(snapshot_cow_threshold, cow_threshold, int, 0644); +static unsigned cow_threshold = DEFAULT_COW_THRESHOLD; +module_param_named(snapshot_cow_threshold, cow_threshold, uint, 0644); MODULE_PARM_DESC(snapshot_cow_threshold, "Maximum number of chunks being copied on write"); DECLARE_DM_KCOPYD_THROTTLE_WITH_MODULE_PARM(snapshot_copy_throttle, @@ -1327,7 +1326,7 @@ static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv) goto bad_hash_tables; } - sema_init(&s->cow_count, (cow_threshold > 0) ? cow_threshold : INT_MAX); + init_waitqueue_head(&s->in_progress_wait); s->kcopyd_client = dm_kcopyd_client_create(&dm_kcopyd_throttle); if (IS_ERR(s->kcopyd_client)) { @@ -1509,17 +1508,54 @@ static void snapshot_dtr(struct dm_target *ti) dm_put_device(ti, s->origin); + WARN_ON(s->in_progress); + kfree(s); } static void account_start_copy(struct dm_snapshot *s) { - down(&s->cow_count); + spin_lock(&s->in_progress_wait.lock); + s->in_progress++; + spin_unlock(&s->in_progress_wait.lock); } static void account_end_copy(struct dm_snapshot *s) { - up(&s->cow_count); + spin_lock(&s->in_progress_wait.lock); + BUG_ON(!s->in_progress); + s->in_progress--; + if (likely(s->in_progress <= cow_threshold) && + unlikely(waitqueue_active(&s->in_progress_wait))) + wake_up_locked(&s->in_progress_wait); + spin_unlock(&s->in_progress_wait.lock); +} + +static bool wait_for_in_progress(struct dm_snapshot *s, bool unlock_origins) +{ + if (unlikely(s->in_progress > cow_threshold)) { + spin_lock(&s->in_progress_wait.lock); + if (likely(s->in_progress > cow_threshold)) { + /* + * NOTE: this throttle doesn't account for whether + * the caller is servicing an IO that will trigger a COW + * so excess throttling may result for chunks not required + * to be COW'd. But if cow_threshold was reached, extra + * throttling is unlikely to negatively impact performance. + */ + DECLARE_WAITQUEUE(wait, current); + __add_wait_queue(&s->in_progress_wait, &wait); + __set_current_state(TASK_UNINTERRUPTIBLE); + spin_unlock(&s->in_progress_wait.lock); + if (unlock_origins) + up_read(&_origins_lock); + io_schedule(); + remove_wait_queue(&s->in_progress_wait, &wait); + return false; + } + spin_unlock(&s->in_progress_wait.lock); + } + return true; } /* @@ -1537,7 +1573,7 @@ static void flush_bios(struct bio *bio) } } -static int do_origin(struct dm_dev *origin, struct bio *bio); +static int do_origin(struct dm_dev *origin, struct bio *bio, bool limit); /* * Flush a list of buffers. @@ -1550,7 +1586,7 @@ static void retry_origin_bios(struct dm_snapshot *s, struct bio *bio) while (bio) { n = bio->bi_next; bio->bi_next = NULL; - r = do_origin(s->origin, bio); + r = do_origin(s->origin, bio, false); if (r == DM_MAPIO_REMAPPED) generic_make_request(bio); bio = n; @@ -1926,6 +1962,11 @@ static int snapshot_map(struct dm_target *ti, struct bio *bio) if (!s->valid) return DM_MAPIO_KILL; + if (bio_data_dir(bio) == WRITE) { + while (unlikely(!wait_for_in_progress(s, false))) + ; /* wait_for_in_progress() has slept */ + } + down_read(&s->lock); dm_exception_table_lock(&lock); @@ -2122,7 +2163,7 @@ static int snapshot_merge_map(struct dm_target *ti, struct bio *bio) if (bio_data_dir(bio) == WRITE) { up_write(&s->lock); - return do_origin(s->origin, bio); + return do_origin(s->origin, bio, false); } out_unlock: @@ -2497,15 +2538,24 @@ static int __origin_write(struct list_head *snapshots, sector_t sector, /* * Called on a write from the origin driver. */ -static int do_origin(struct dm_dev *origin, struct bio *bio) +static int do_origin(struct dm_dev *origin, struct bio *bio, bool limit) { struct origin *o; int r = DM_MAPIO_REMAPPED; +again: down_read(&_origins_lock); o = __lookup_origin(origin->bdev); - if (o) + if (o) { + if (limit) { + struct dm_snapshot *s; + list_for_each_entry(s, &o->snapshots, list) + if (unlikely(!wait_for_in_progress(s, true))) + goto again; + } + r = __origin_write(&o->snapshots, bio->bi_iter.bi_sector, bio); + } up_read(&_origins_lock); return r; @@ -2618,7 +2668,7 @@ static int origin_map(struct dm_target *ti, struct bio *bio) dm_accept_partial_bio(bio, available_sectors); /* Only tell snapshots if this is a write */ - return do_origin(o->dev, bio); + return do_origin(o->dev, bio, true); } /*

5 years, 2 months

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FAILED: patch "[PATCH] dm snapshot: rework COW throttling to fix deadlock" failed to apply to 4.14-stable tree

by gregkh＠linuxfoundation.org

The patch below does not apply to the 4.14-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable(a)vger.kernel.org>. thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From b21555786f18cd77f2311ad89074533109ae3ffa Mon Sep 17 00:00:00 2001 From: Mikulas Patocka <mpatocka(a)redhat.com> Date: Wed, 2 Oct 2019 06:15:53 -0400 Subject: [PATCH] dm snapshot: rework COW throttling to fix deadlock Commit 721b1d98fb517a ("dm snapshot: Fix excessive memory usage and workqueue stalls") introduced a semaphore to limit the maximum number of in-flight kcopyd (COW) jobs. The implementation of this throttling mechanism is prone to a deadlock: 1. One or more threads write to the origin device causing COW, which is performed by kcopyd. 2. At some point some of these threads might reach the s->cow_count semaphore limit and block in down(&s->cow_count), holding a read lock on _origins_lock. 3. Someone tries to acquire a write lock on _origins_lock, e.g., snapshot_ctr(), which blocks because the threads at step (2) already hold a read lock on it. 4. A COW operation completes and kcopyd runs dm-snapshot's completion callback, which ends up calling pending_complete(). pending_complete() tries to resubmit any deferred origin bios. This requires acquiring a read lock on _origins_lock, which blocks. This happens because the read-write semaphore implementation gives priority to writers, meaning that as soon as a writer tries to enter the critical section, no readers will be allowed in, until all writers have completed their work. So, pending_complete() waits for the writer at step (3) to acquire and release the lock. This writer waits for the readers at step (2) to release the read lock and those readers wait for pending_complete() (the kcopyd thread) to signal the s->cow_count semaphore: DEADLOCK. The above was thoroughly analyzed and documented by Nikos Tsironis as part of his initial proposal for fixing this deadlock, see: https://www.redhat.com/archives/dm-devel/2019-October/msg00001.html Fix this deadlock by reworking COW throttling so that it waits without holding any locks. Add a variable 'in_progress' that counts how many kcopyd jobs are running. A function wait_for_in_progress() will sleep if 'in_progress' is over the limit. It drops _origins_lock in order to avoid the deadlock. Reported-by: Guruswamy Basavaiah <guru2018(a)gmail.com> Reported-by: Nikos Tsironis <ntsironis(a)arrikto.com> Reviewed-by: Nikos Tsironis <ntsironis(a)arrikto.com> Tested-by: Nikos Tsironis <ntsironis(a)arrikto.com> Fixes: 721b1d98fb51 ("dm snapshot: Fix excessive memory usage and workqueue stalls") Cc: stable(a)vger.kernel.org # v5.0+ Depends-on: 4a3f111a73a8c ("dm snapshot: introduce account_start_copy() and account_end_copy()") Signed-off-by: Mikulas Patocka <mpatocka(a)redhat.com> Signed-off-by: Mike Snitzer <snitzer(a)redhat.com> diff --git a/drivers/md/dm-snap.c b/drivers/md/dm-snap.c index da3bd1794ee0..4fb1a40e68a0 100644 --- a/drivers/md/dm-snap.c +++ b/drivers/md/dm-snap.c @@ -18,7 +18,6 @@ #include <linux/vmalloc.h> #include <linux/log2.h> #include <linux/dm-kcopyd.h> -#include <linux/semaphore.h> #include "dm.h" @@ -107,8 +106,8 @@ struct dm_snapshot { /* The on disk metadata handler */ struct dm_exception_store *store; - /* Maximum number of in-flight COW jobs. */ - struct semaphore cow_count; + unsigned in_progress; + struct wait_queue_head in_progress_wait; struct dm_kcopyd_client *kcopyd_client; @@ -162,8 +161,8 @@ struct dm_snapshot { */ #define DEFAULT_COW_THRESHOLD 2048 -static int cow_threshold = DEFAULT_COW_THRESHOLD; -module_param_named(snapshot_cow_threshold, cow_threshold, int, 0644); +static unsigned cow_threshold = DEFAULT_COW_THRESHOLD; +module_param_named(snapshot_cow_threshold, cow_threshold, uint, 0644); MODULE_PARM_DESC(snapshot_cow_threshold, "Maximum number of chunks being copied on write"); DECLARE_DM_KCOPYD_THROTTLE_WITH_MODULE_PARM(snapshot_copy_throttle, @@ -1327,7 +1326,7 @@ static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv) goto bad_hash_tables; } - sema_init(&s->cow_count, (cow_threshold > 0) ? cow_threshold : INT_MAX); + init_waitqueue_head(&s->in_progress_wait); s->kcopyd_client = dm_kcopyd_client_create(&dm_kcopyd_throttle); if (IS_ERR(s->kcopyd_client)) { @@ -1509,17 +1508,54 @@ static void snapshot_dtr(struct dm_target *ti) dm_put_device(ti, s->origin); + WARN_ON(s->in_progress); + kfree(s); } static void account_start_copy(struct dm_snapshot *s) { - down(&s->cow_count); + spin_lock(&s->in_progress_wait.lock); + s->in_progress++; + spin_unlock(&s->in_progress_wait.lock); } static void account_end_copy(struct dm_snapshot *s) { - up(&s->cow_count); + spin_lock(&s->in_progress_wait.lock); + BUG_ON(!s->in_progress); + s->in_progress--; + if (likely(s->in_progress <= cow_threshold) && + unlikely(waitqueue_active(&s->in_progress_wait))) + wake_up_locked(&s->in_progress_wait); + spin_unlock(&s->in_progress_wait.lock); +} + +static bool wait_for_in_progress(struct dm_snapshot *s, bool unlock_origins) +{ + if (unlikely(s->in_progress > cow_threshold)) { + spin_lock(&s->in_progress_wait.lock); + if (likely(s->in_progress > cow_threshold)) { + /* + * NOTE: this throttle doesn't account for whether + * the caller is servicing an IO that will trigger a COW + * so excess throttling may result for chunks not required + * to be COW'd. But if cow_threshold was reached, extra + * throttling is unlikely to negatively impact performance. + */ + DECLARE_WAITQUEUE(wait, current); + __add_wait_queue(&s->in_progress_wait, &wait); + __set_current_state(TASK_UNINTERRUPTIBLE); + spin_unlock(&s->in_progress_wait.lock); + if (unlock_origins) + up_read(&_origins_lock); + io_schedule(); + remove_wait_queue(&s->in_progress_wait, &wait); + return false; + } + spin_unlock(&s->in_progress_wait.lock); + } + return true; } /* @@ -1537,7 +1573,7 @@ static void flush_bios(struct bio *bio) } } -static int do_origin(struct dm_dev *origin, struct bio *bio); +static int do_origin(struct dm_dev *origin, struct bio *bio, bool limit); /* * Flush a list of buffers. @@ -1550,7 +1586,7 @@ static void retry_origin_bios(struct dm_snapshot *s, struct bio *bio) while (bio) { n = bio->bi_next; bio->bi_next = NULL; - r = do_origin(s->origin, bio); + r = do_origin(s->origin, bio, false); if (r == DM_MAPIO_REMAPPED) generic_make_request(bio); bio = n; @@ -1926,6 +1962,11 @@ static int snapshot_map(struct dm_target *ti, struct bio *bio) if (!s->valid) return DM_MAPIO_KILL; + if (bio_data_dir(bio) == WRITE) { + while (unlikely(!wait_for_in_progress(s, false))) + ; /* wait_for_in_progress() has slept */ + } + down_read(&s->lock); dm_exception_table_lock(&lock); @@ -2122,7 +2163,7 @@ static int snapshot_merge_map(struct dm_target *ti, struct bio *bio) if (bio_data_dir(bio) == WRITE) { up_write(&s->lock); - return do_origin(s->origin, bio); + return do_origin(s->origin, bio, false); } out_unlock: @@ -2497,15 +2538,24 @@ static int __origin_write(struct list_head *snapshots, sector_t sector, /* * Called on a write from the origin driver. */ -static int do_origin(struct dm_dev *origin, struct bio *bio) +static int do_origin(struct dm_dev *origin, struct bio *bio, bool limit) { struct origin *o; int r = DM_MAPIO_REMAPPED; +again: down_read(&_origins_lock); o = __lookup_origin(origin->bdev); - if (o) + if (o) { + if (limit) { + struct dm_snapshot *s; + list_for_each_entry(s, &o->snapshots, list) + if (unlikely(!wait_for_in_progress(s, true))) + goto again; + } + r = __origin_write(&o->snapshots, bio->bi_iter.bi_sector, bio); + } up_read(&_origins_lock); return r; @@ -2618,7 +2668,7 @@ static int origin_map(struct dm_target *ti, struct bio *bio) dm_accept_partial_bio(bio, available_sectors); /* Only tell snapshots if this is a write */ - return do_origin(o->dev, bio); + return do_origin(o->dev, bio, true); } /*

5 years, 2 months

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FAILED: patch "[PATCH] dm snapshot: rework COW throttling to fix deadlock" failed to apply to 4.19-stable tree

by gregkh＠linuxfoundation.org

The patch below does not apply to the 4.19-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable(a)vger.kernel.org>. thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From b21555786f18cd77f2311ad89074533109ae3ffa Mon Sep 17 00:00:00 2001 From: Mikulas Patocka <mpatocka(a)redhat.com> Date: Wed, 2 Oct 2019 06:15:53 -0400 Subject: [PATCH] dm snapshot: rework COW throttling to fix deadlock Commit 721b1d98fb517a ("dm snapshot: Fix excessive memory usage and workqueue stalls") introduced a semaphore to limit the maximum number of in-flight kcopyd (COW) jobs. The implementation of this throttling mechanism is prone to a deadlock: 1. One or more threads write to the origin device causing COW, which is performed by kcopyd. 2. At some point some of these threads might reach the s->cow_count semaphore limit and block in down(&s->cow_count), holding a read lock on _origins_lock. 3. Someone tries to acquire a write lock on _origins_lock, e.g., snapshot_ctr(), which blocks because the threads at step (2) already hold a read lock on it. 4. A COW operation completes and kcopyd runs dm-snapshot's completion callback, which ends up calling pending_complete(). pending_complete() tries to resubmit any deferred origin bios. This requires acquiring a read lock on _origins_lock, which blocks. This happens because the read-write semaphore implementation gives priority to writers, meaning that as soon as a writer tries to enter the critical section, no readers will be allowed in, until all writers have completed their work. So, pending_complete() waits for the writer at step (3) to acquire and release the lock. This writer waits for the readers at step (2) to release the read lock and those readers wait for pending_complete() (the kcopyd thread) to signal the s->cow_count semaphore: DEADLOCK. The above was thoroughly analyzed and documented by Nikos Tsironis as part of his initial proposal for fixing this deadlock, see: https://www.redhat.com/archives/dm-devel/2019-October/msg00001.html Fix this deadlock by reworking COW throttling so that it waits without holding any locks. Add a variable 'in_progress' that counts how many kcopyd jobs are running. A function wait_for_in_progress() will sleep if 'in_progress' is over the limit. It drops _origins_lock in order to avoid the deadlock. Reported-by: Guruswamy Basavaiah <guru2018(a)gmail.com> Reported-by: Nikos Tsironis <ntsironis(a)arrikto.com> Reviewed-by: Nikos Tsironis <ntsironis(a)arrikto.com> Tested-by: Nikos Tsironis <ntsironis(a)arrikto.com> Fixes: 721b1d98fb51 ("dm snapshot: Fix excessive memory usage and workqueue stalls") Cc: stable(a)vger.kernel.org # v5.0+ Depends-on: 4a3f111a73a8c ("dm snapshot: introduce account_start_copy() and account_end_copy()") Signed-off-by: Mikulas Patocka <mpatocka(a)redhat.com> Signed-off-by: Mike Snitzer <snitzer(a)redhat.com> diff --git a/drivers/md/dm-snap.c b/drivers/md/dm-snap.c index da3bd1794ee0..4fb1a40e68a0 100644 --- a/drivers/md/dm-snap.c +++ b/drivers/md/dm-snap.c @@ -18,7 +18,6 @@ #include <linux/vmalloc.h> #include <linux/log2.h> #include <linux/dm-kcopyd.h> -#include <linux/semaphore.h> #include "dm.h" @@ -107,8 +106,8 @@ struct dm_snapshot { /* The on disk metadata handler */ struct dm_exception_store *store; - /* Maximum number of in-flight COW jobs. */ - struct semaphore cow_count; + unsigned in_progress; + struct wait_queue_head in_progress_wait; struct dm_kcopyd_client *kcopyd_client; @@ -162,8 +161,8 @@ struct dm_snapshot { */ #define DEFAULT_COW_THRESHOLD 2048 -static int cow_threshold = DEFAULT_COW_THRESHOLD; -module_param_named(snapshot_cow_threshold, cow_threshold, int, 0644); +static unsigned cow_threshold = DEFAULT_COW_THRESHOLD; +module_param_named(snapshot_cow_threshold, cow_threshold, uint, 0644); MODULE_PARM_DESC(snapshot_cow_threshold, "Maximum number of chunks being copied on write"); DECLARE_DM_KCOPYD_THROTTLE_WITH_MODULE_PARM(snapshot_copy_throttle, @@ -1327,7 +1326,7 @@ static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv) goto bad_hash_tables; } - sema_init(&s->cow_count, (cow_threshold > 0) ? cow_threshold : INT_MAX); + init_waitqueue_head(&s->in_progress_wait); s->kcopyd_client = dm_kcopyd_client_create(&dm_kcopyd_throttle); if (IS_ERR(s->kcopyd_client)) { @@ -1509,17 +1508,54 @@ static void snapshot_dtr(struct dm_target *ti) dm_put_device(ti, s->origin); + WARN_ON(s->in_progress); + kfree(s); } static void account_start_copy(struct dm_snapshot *s) { - down(&s->cow_count); + spin_lock(&s->in_progress_wait.lock); + s->in_progress++; + spin_unlock(&s->in_progress_wait.lock); } static void account_end_copy(struct dm_snapshot *s) { - up(&s->cow_count); + spin_lock(&s->in_progress_wait.lock); + BUG_ON(!s->in_progress); + s->in_progress--; + if (likely(s->in_progress <= cow_threshold) && + unlikely(waitqueue_active(&s->in_progress_wait))) + wake_up_locked(&s->in_progress_wait); + spin_unlock(&s->in_progress_wait.lock); +} + +static bool wait_for_in_progress(struct dm_snapshot *s, bool unlock_origins) +{ + if (unlikely(s->in_progress > cow_threshold)) { + spin_lock(&s->in_progress_wait.lock); + if (likely(s->in_progress > cow_threshold)) { + /* + * NOTE: this throttle doesn't account for whether + * the caller is servicing an IO that will trigger a COW + * so excess throttling may result for chunks not required + * to be COW'd. But if cow_threshold was reached, extra + * throttling is unlikely to negatively impact performance. + */ + DECLARE_WAITQUEUE(wait, current); + __add_wait_queue(&s->in_progress_wait, &wait); + __set_current_state(TASK_UNINTERRUPTIBLE); + spin_unlock(&s->in_progress_wait.lock); + if (unlock_origins) + up_read(&_origins_lock); + io_schedule(); + remove_wait_queue(&s->in_progress_wait, &wait); + return false; + } + spin_unlock(&s->in_progress_wait.lock); + } + return true; } /* @@ -1537,7 +1573,7 @@ static void flush_bios(struct bio *bio) } } -static int do_origin(struct dm_dev *origin, struct bio *bio); +static int do_origin(struct dm_dev *origin, struct bio *bio, bool limit); /* * Flush a list of buffers. @@ -1550,7 +1586,7 @@ static void retry_origin_bios(struct dm_snapshot *s, struct bio *bio) while (bio) { n = bio->bi_next; bio->bi_next = NULL; - r = do_origin(s->origin, bio); + r = do_origin(s->origin, bio, false); if (r == DM_MAPIO_REMAPPED) generic_make_request(bio); bio = n; @@ -1926,6 +1962,11 @@ static int snapshot_map(struct dm_target *ti, struct bio *bio) if (!s->valid) return DM_MAPIO_KILL; + if (bio_data_dir(bio) == WRITE) { + while (unlikely(!wait_for_in_progress(s, false))) + ; /* wait_for_in_progress() has slept */ + } + down_read(&s->lock); dm_exception_table_lock(&lock); @@ -2122,7 +2163,7 @@ static int snapshot_merge_map(struct dm_target *ti, struct bio *bio) if (bio_data_dir(bio) == WRITE) { up_write(&s->lock); - return do_origin(s->origin, bio); + return do_origin(s->origin, bio, false); } out_unlock: @@ -2497,15 +2538,24 @@ static int __origin_write(struct list_head *snapshots, sector_t sector, /* * Called on a write from the origin driver. */ -static int do_origin(struct dm_dev *origin, struct bio *bio) +static int do_origin(struct dm_dev *origin, struct bio *bio, bool limit) { struct origin *o; int r = DM_MAPIO_REMAPPED; +again: down_read(&_origins_lock); o = __lookup_origin(origin->bdev); - if (o) + if (o) { + if (limit) { + struct dm_snapshot *s; + list_for_each_entry(s, &o->snapshots, list) + if (unlikely(!wait_for_in_progress(s, true))) + goto again; + } + r = __origin_write(&o->snapshots, bio->bi_iter.bi_sector, bio); + } up_read(&_origins_lock); return r; @@ -2618,7 +2668,7 @@ static int origin_map(struct dm_target *ti, struct bio *bio) dm_accept_partial_bio(bio, available_sectors); /* Only tell snapshots if this is a write */ - return do_origin(o->dev, bio); + return do_origin(o->dev, bio, true); } /*

5 years, 2 months

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