I'm occasionally seeing a kmemleak warning in xfstest generic/013:
unreferenced object 0xffff8881fccca940 (size 32): comm "kworker/0:1", pid 12, jiffies 4295005883 (age 130.648s) hex dump (first 32 bytes): 01 00 00 00 00 00 00 00 01 00 00 00 00 00 00 00 ................ 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ backtrace: [<00000000d741a1ea>] build_snap_context+0x5b/0x2a0 [<0000000021a00533>] rebuild_snap_realms+0x27/0x90 [<00000000ac538600>] rebuild_snap_realms+0x42/0x90 [<000000000e955fac>] ceph_update_snap_trace+0x2ee/0x610 [<00000000a9550416>] ceph_handle_snap+0x317/0x5f3 [<00000000fc287b83>] dispatch+0x362/0x176c [<00000000a312c741>] ceph_con_workfn+0x9ce/0x2cf0 [<000000004168e3a9>] process_one_work+0x1d4/0x400 [<000000002188e9e7>] worker_thread+0x2d/0x3c0 [<00000000b593e4b3>] kthread+0x112/0x130 [<00000000a8587dca>] ret_from_fork+0x35/0x40 [<00000000ba1c9c1d>] 0xffffffffffffffff
It looks like it is possible that we miss a flush_ack from the MDS when, for example, umounting the filesystem. In that case, we can simply drop the reference to the ceph_snap_context obtained in ceph_queue_cap_snap().
Link: https://tracker.ceph.com/issues/38224 Cc: stable@vger.kernel.org Signed-off-by: Luis Henriques lhenriques@suse.com --- fs/ceph/caps.c | 7 +++++++ 1 file changed, 7 insertions(+)
diff --git a/fs/ceph/caps.c b/fs/ceph/caps.c index 36a8dc699448..208f4dc6f574 100644 --- a/fs/ceph/caps.c +++ b/fs/ceph/caps.c @@ -1054,6 +1054,7 @@ int ceph_is_any_caps(struct inode *inode) static void drop_inode_snap_realm(struct ceph_inode_info *ci) { struct ceph_snap_realm *realm = ci->i_snap_realm; + spin_lock(&realm->inodes_with_caps_lock); list_del_init(&ci->i_snap_realm_item); ci->i_snap_realm_counter++; @@ -1063,6 +1064,12 @@ static void drop_inode_snap_realm(struct ceph_inode_info *ci) spin_unlock(&realm->inodes_with_caps_lock); ceph_put_snap_realm(ceph_sb_to_client(ci->vfs_inode.i_sb)->mdsc, realm); + /* + * ci->i_head_snapc should be NULL, but we may still be waiting for a + * flush_ack from the MDS. In that case, we still hold a ref for the + * ceph_snap_context and we need to drop it. + */ + ceph_put_snap_context(ci->i_head_snapc); }
/*
On Fri, Mar 15, 2019 at 7:13 PM Luis Henriques lhenriques@suse.com wrote:
I'm occasionally seeing a kmemleak warning in xfstest generic/013:
unreferenced object 0xffff8881fccca940 (size 32): comm "kworker/0:1", pid 12, jiffies 4295005883 (age 130.648s) hex dump (first 32 bytes): 01 00 00 00 00 00 00 00 01 00 00 00 00 00 00 00 ................ 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ backtrace: [<00000000d741a1ea>] build_snap_context+0x5b/0x2a0 [<0000000021a00533>] rebuild_snap_realms+0x27/0x90 [<00000000ac538600>] rebuild_snap_realms+0x42/0x90 [<000000000e955fac>] ceph_update_snap_trace+0x2ee/0x610 [<00000000a9550416>] ceph_handle_snap+0x317/0x5f3 [<00000000fc287b83>] dispatch+0x362/0x176c [<00000000a312c741>] ceph_con_workfn+0x9ce/0x2cf0 [<000000004168e3a9>] process_one_work+0x1d4/0x400 [<000000002188e9e7>] worker_thread+0x2d/0x3c0 [<00000000b593e4b3>] kthread+0x112/0x130 [<00000000a8587dca>] ret_from_fork+0x35/0x40 [<00000000ba1c9c1d>] 0xffffffffffffffff
It looks like it is possible that we miss a flush_ack from the MDS when, for example, umounting the filesystem. In that case, we can simply drop the reference to the ceph_snap_context obtained in ceph_queue_cap_snap().
Link: https://tracker.ceph.com/issues/38224 Cc: stable@vger.kernel.org Signed-off-by: Luis Henriques lhenriques@suse.com
fs/ceph/caps.c | 7 +++++++ 1 file changed, 7 insertions(+)
diff --git a/fs/ceph/caps.c b/fs/ceph/caps.c index 36a8dc699448..208f4dc6f574 100644 --- a/fs/ceph/caps.c +++ b/fs/ceph/caps.c @@ -1054,6 +1054,7 @@ int ceph_is_any_caps(struct inode *inode) static void drop_inode_snap_realm(struct ceph_inode_info *ci) { struct ceph_snap_realm *realm = ci->i_snap_realm;
spin_lock(&realm->inodes_with_caps_lock); list_del_init(&ci->i_snap_realm_item); ci->i_snap_realm_counter++;@@ -1063,6 +1064,12 @@ static void drop_inode_snap_realm(struct ceph_inode_info *ci) spin_unlock(&realm->inodes_with_caps_lock); ceph_put_snap_realm(ceph_sb_to_client(ci->vfs_inode.i_sb)->mdsc, realm);
/** ci->i_head_snapc should be NULL, but we may still be waiting for a* flush_ack from the MDS. In that case, we still hold a ref for the* ceph_snap_context and we need to drop it.*/ceph_put_snap_context(ci->i_head_snapc);}
/*
This does not seem right. i_head_snapc is cleared when (ci->i_wrbuffer_ref_head == 0 && ci->i_dirty_caps == 0 && ci->i_flushing_caps == 0) . Nothing do with dropping ci->i_snap_realm. Did you see 'reconnect denied' during the test? If you did, the fix should be in iterate_session_caps()
"Yan, Zheng" ukernel@gmail.com writes:
On Fri, Mar 15, 2019 at 7:13 PM Luis Henriques lhenriques@suse.com wrote:
I'm occasionally seeing a kmemleak warning in xfstest generic/013:
unreferenced object 0xffff8881fccca940 (size 32): comm "kworker/0:1", pid 12, jiffies 4295005883 (age 130.648s) hex dump (first 32 bytes): 01 00 00 00 00 00 00 00 01 00 00 00 00 00 00 00 ................ 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ backtrace: [<00000000d741a1ea>] build_snap_context+0x5b/0x2a0 [<0000000021a00533>] rebuild_snap_realms+0x27/0x90 [<00000000ac538600>] rebuild_snap_realms+0x42/0x90 [<000000000e955fac>] ceph_update_snap_trace+0x2ee/0x610 [<00000000a9550416>] ceph_handle_snap+0x317/0x5f3 [<00000000fc287b83>] dispatch+0x362/0x176c [<00000000a312c741>] ceph_con_workfn+0x9ce/0x2cf0 [<000000004168e3a9>] process_one_work+0x1d4/0x400 [<000000002188e9e7>] worker_thread+0x2d/0x3c0 [<00000000b593e4b3>] kthread+0x112/0x130 [<00000000a8587dca>] ret_from_fork+0x35/0x40 [<00000000ba1c9c1d>] 0xffffffffffffffff
It looks like it is possible that we miss a flush_ack from the MDS when, for example, umounting the filesystem. In that case, we can simply drop the reference to the ceph_snap_context obtained in ceph_queue_cap_snap().
Link: https://tracker.ceph.com/issues/38224 Cc: stable@vger.kernel.org Signed-off-by: Luis Henriques lhenriques@suse.com
fs/ceph/caps.c | 7 +++++++ 1 file changed, 7 insertions(+)
diff --git a/fs/ceph/caps.c b/fs/ceph/caps.c index 36a8dc699448..208f4dc6f574 100644 --- a/fs/ceph/caps.c +++ b/fs/ceph/caps.c @@ -1054,6 +1054,7 @@ int ceph_is_any_caps(struct inode *inode) static void drop_inode_snap_realm(struct ceph_inode_info *ci) { struct ceph_snap_realm *realm = ci->i_snap_realm;
spin_lock(&realm->inodes_with_caps_lock); list_del_init(&ci->i_snap_realm_item); ci->i_snap_realm_counter++;@@ -1063,6 +1064,12 @@ static void drop_inode_snap_realm(struct ceph_inode_info *ci) spin_unlock(&realm->inodes_with_caps_lock); ceph_put_snap_realm(ceph_sb_to_client(ci->vfs_inode.i_sb)->mdsc, realm);
/** ci->i_head_snapc should be NULL, but we may still be waiting for a* flush_ack from the MDS. In that case, we still hold a ref for the* ceph_snap_context and we need to drop it.*/ceph_put_snap_context(ci->i_head_snapc);}
/*
This does not seem right. i_head_snapc is cleared when (ci->i_wrbuffer_ref_head == 0 && ci->i_dirty_caps == 0 && ci->i_flushing_caps == 0) . Nothing do with dropping ci->i_snap_realm. Did you see 'reconnect denied' during the test? If you did, the fix should be in iterate_session_caps()
No, I didn't saw any 'reconnect denied' in the test. The test actually seems to execute fine, except from the memory leak.
It's very difficult to reproduce this issue, but last time I managed to get this memory leak to trigger I actually had some debugging code in drop_inode_snap_realm, something like:
if (ci->i_head_snapc) printk("i_head_snapc: 0x%px\n", ci->i_head_snapc);
This printk was only executed when the bug triggered (during a filesystem umount) and the address shown was the same as in the kmemleak warning.
After spending some time looking, I assumed this to be a missing call to handle_cap_flush_ack, which would do the i_head_snapc cleanup.
Cheers,
On Mon, Mar 18, 2019 at 6:33 PM Luis Henriques lhenriques@suse.com wrote:
"Yan, Zheng" ukernel@gmail.com writes:
On Fri, Mar 15, 2019 at 7:13 PM Luis Henriques lhenriques@suse.com wrote:
I'm occasionally seeing a kmemleak warning in xfstest generic/013:
unreferenced object 0xffff8881fccca940 (size 32): comm "kworker/0:1", pid 12, jiffies 4295005883 (age 130.648s) hex dump (first 32 bytes): 01 00 00 00 00 00 00 00 01 00 00 00 00 00 00 00 ................ 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ backtrace: [<00000000d741a1ea>] build_snap_context+0x5b/0x2a0 [<0000000021a00533>] rebuild_snap_realms+0x27/0x90 [<00000000ac538600>] rebuild_snap_realms+0x42/0x90 [<000000000e955fac>] ceph_update_snap_trace+0x2ee/0x610 [<00000000a9550416>] ceph_handle_snap+0x317/0x5f3 [<00000000fc287b83>] dispatch+0x362/0x176c [<00000000a312c741>] ceph_con_workfn+0x9ce/0x2cf0 [<000000004168e3a9>] process_one_work+0x1d4/0x400 [<000000002188e9e7>] worker_thread+0x2d/0x3c0 [<00000000b593e4b3>] kthread+0x112/0x130 [<00000000a8587dca>] ret_from_fork+0x35/0x40 [<00000000ba1c9c1d>] 0xffffffffffffffff
It looks like it is possible that we miss a flush_ack from the MDS when, for example, umounting the filesystem. In that case, we can simply drop the reference to the ceph_snap_context obtained in ceph_queue_cap_snap().
Link: https://tracker.ceph.com/issues/38224 Cc: stable@vger.kernel.org Signed-off-by: Luis Henriques lhenriques@suse.com
fs/ceph/caps.c | 7 +++++++ 1 file changed, 7 insertions(+)
diff --git a/fs/ceph/caps.c b/fs/ceph/caps.c index 36a8dc699448..208f4dc6f574 100644 --- a/fs/ceph/caps.c +++ b/fs/ceph/caps.c @@ -1054,6 +1054,7 @@ int ceph_is_any_caps(struct inode *inode) static void drop_inode_snap_realm(struct ceph_inode_info *ci) { struct ceph_snap_realm *realm = ci->i_snap_realm;
spin_lock(&realm->inodes_with_caps_lock); list_del_init(&ci->i_snap_realm_item); ci->i_snap_realm_counter++;@@ -1063,6 +1064,12 @@ static void drop_inode_snap_realm(struct ceph_inode_info *ci) spin_unlock(&realm->inodes_with_caps_lock); ceph_put_snap_realm(ceph_sb_to_client(ci->vfs_inode.i_sb)->mdsc, realm);
/** ci->i_head_snapc should be NULL, but we may still be waiting for a* flush_ack from the MDS. In that case, we still hold a ref for the* ceph_snap_context and we need to drop it.*/ceph_put_snap_context(ci->i_head_snapc);}
/*
This does not seem right. i_head_snapc is cleared when (ci->i_wrbuffer_ref_head == 0 && ci->i_dirty_caps == 0 && ci->i_flushing_caps == 0) . Nothing do with dropping ci->i_snap_realm. Did you see 'reconnect denied' during the test? If you did, the fix should be in iterate_session_caps()
No, I didn't saw any 'reconnect denied' in the test. The test actually seems to execute fine, except from the memory leak.
It's very difficult to reproduce this issue, but last time I managed to get this memory leak to trigger I actually had some debugging code in drop_inode_snap_realm, something like:
if (ci->i_head_snapc) printk("i_head_snapc: 0x%px\n", ci->i_head_snapc);
please add code that prints i_wrbuffer_ref_head, i_dirty_caps, i_flushing_caps. and try reproducing it again.
This printk was only executed when the bug triggered (during a filesystem umount) and the address shown was the same as in the kmemleak warning.
After spending some time looking, I assumed this to be a missing call to handle_cap_flush_ack, which would do the i_head_snapc cleanup.
Cheers,
Luis
"Yan, Zheng" ukernel@gmail.com writes:
On Mon, Mar 18, 2019 at 6:33 PM Luis Henriques lhenriques@suse.com wrote:
"Yan, Zheng" ukernel@gmail.com writes:
On Fri, Mar 15, 2019 at 7:13 PM Luis Henriques lhenriques@suse.com wrote:
I'm occasionally seeing a kmemleak warning in xfstest generic/013:
unreferenced object 0xffff8881fccca940 (size 32): comm "kworker/0:1", pid 12, jiffies 4295005883 (age 130.648s) hex dump (first 32 bytes): 01 00 00 00 00 00 00 00 01 00 00 00 00 00 00 00 ................ 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ backtrace: [<00000000d741a1ea>] build_snap_context+0x5b/0x2a0 [<0000000021a00533>] rebuild_snap_realms+0x27/0x90 [<00000000ac538600>] rebuild_snap_realms+0x42/0x90 [<000000000e955fac>] ceph_update_snap_trace+0x2ee/0x610 [<00000000a9550416>] ceph_handle_snap+0x317/0x5f3 [<00000000fc287b83>] dispatch+0x362/0x176c [<00000000a312c741>] ceph_con_workfn+0x9ce/0x2cf0 [<000000004168e3a9>] process_one_work+0x1d4/0x400 [<000000002188e9e7>] worker_thread+0x2d/0x3c0 [<00000000b593e4b3>] kthread+0x112/0x130 [<00000000a8587dca>] ret_from_fork+0x35/0x40 [<00000000ba1c9c1d>] 0xffffffffffffffff
It looks like it is possible that we miss a flush_ack from the MDS when, for example, umounting the filesystem. In that case, we can simply drop the reference to the ceph_snap_context obtained in ceph_queue_cap_snap().
Link: https://tracker.ceph.com/issues/38224 Cc: stable@vger.kernel.org Signed-off-by: Luis Henriques lhenriques@suse.com
fs/ceph/caps.c | 7 +++++++ 1 file changed, 7 insertions(+)
diff --git a/fs/ceph/caps.c b/fs/ceph/caps.c index 36a8dc699448..208f4dc6f574 100644 --- a/fs/ceph/caps.c +++ b/fs/ceph/caps.c @@ -1054,6 +1054,7 @@ int ceph_is_any_caps(struct inode *inode) static void drop_inode_snap_realm(struct ceph_inode_info *ci) { struct ceph_snap_realm *realm = ci->i_snap_realm;
spin_lock(&realm->inodes_with_caps_lock); list_del_init(&ci->i_snap_realm_item); ci->i_snap_realm_counter++;@@ -1063,6 +1064,12 @@ static void drop_inode_snap_realm(struct ceph_inode_info *ci) spin_unlock(&realm->inodes_with_caps_lock); ceph_put_snap_realm(ceph_sb_to_client(ci->vfs_inode.i_sb)->mdsc, realm);
/** ci->i_head_snapc should be NULL, but we may still be waiting for a* flush_ack from the MDS. In that case, we still hold a ref for the* ceph_snap_context and we need to drop it.*/ceph_put_snap_context(ci->i_head_snapc);}
/*
This does not seem right. i_head_snapc is cleared when (ci->i_wrbuffer_ref_head == 0 && ci->i_dirty_caps == 0 && ci->i_flushing_caps == 0) . Nothing do with dropping ci->i_snap_realm. Did you see 'reconnect denied' during the test? If you did, the fix should be in iterate_session_caps()
No, I didn't saw any 'reconnect denied' in the test. The test actually seems to execute fine, except from the memory leak.
It's very difficult to reproduce this issue, but last time I managed to get this memory leak to trigger I actually had some debugging code in drop_inode_snap_realm, something like:
if (ci->i_head_snapc) printk("i_head_snapc: 0x%px\n", ci->i_head_snapc);
please add code that prints i_wrbuffer_ref_head, i_dirty_caps, i_flushing_caps. and try reproducing it again.
Ok, it took me a few hours, but I managed to reproduce the bug, with those extra printks. All those values are set to 0 when the bug triggers (and i_head_snapc != NULL).
Cheers,
On Tue, Mar 19, 2019 at 12:22 AM Luis Henriques lhenriques@suse.com wrote:
"Yan, Zheng" ukernel@gmail.com writes:
On Mon, Mar 18, 2019 at 6:33 PM Luis Henriques lhenriques@suse.com wrote:
"Yan, Zheng" ukernel@gmail.com writes:
On Fri, Mar 15, 2019 at 7:13 PM Luis Henriques lhenriques@suse.com wrote:
I'm occasionally seeing a kmemleak warning in xfstest generic/013:
unreferenced object 0xffff8881fccca940 (size 32): comm "kworker/0:1", pid 12, jiffies 4295005883 (age 130.648s) hex dump (first 32 bytes): 01 00 00 00 00 00 00 00 01 00 00 00 00 00 00 00 ................ 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ backtrace: [<00000000d741a1ea>] build_snap_context+0x5b/0x2a0 [<0000000021a00533>] rebuild_snap_realms+0x27/0x90 [<00000000ac538600>] rebuild_snap_realms+0x42/0x90 [<000000000e955fac>] ceph_update_snap_trace+0x2ee/0x610 [<00000000a9550416>] ceph_handle_snap+0x317/0x5f3 [<00000000fc287b83>] dispatch+0x362/0x176c [<00000000a312c741>] ceph_con_workfn+0x9ce/0x2cf0 [<000000004168e3a9>] process_one_work+0x1d4/0x400 [<000000002188e9e7>] worker_thread+0x2d/0x3c0 [<00000000b593e4b3>] kthread+0x112/0x130 [<00000000a8587dca>] ret_from_fork+0x35/0x40 [<00000000ba1c9c1d>] 0xffffffffffffffff
It looks like it is possible that we miss a flush_ack from the MDS when, for example, umounting the filesystem. In that case, we can simply drop the reference to the ceph_snap_context obtained in ceph_queue_cap_snap().
Link: https://tracker.ceph.com/issues/38224 Cc: stable@vger.kernel.org Signed-off-by: Luis Henriques lhenriques@suse.com
fs/ceph/caps.c | 7 +++++++ 1 file changed, 7 insertions(+)
diff --git a/fs/ceph/caps.c b/fs/ceph/caps.c index 36a8dc699448..208f4dc6f574 100644 --- a/fs/ceph/caps.c +++ b/fs/ceph/caps.c @@ -1054,6 +1054,7 @@ int ceph_is_any_caps(struct inode *inode) static void drop_inode_snap_realm(struct ceph_inode_info *ci) { struct ceph_snap_realm *realm = ci->i_snap_realm;
spin_lock(&realm->inodes_with_caps_lock); list_del_init(&ci->i_snap_realm_item); ci->i_snap_realm_counter++;@@ -1063,6 +1064,12 @@ static void drop_inode_snap_realm(struct ceph_inode_info *ci) spin_unlock(&realm->inodes_with_caps_lock); ceph_put_snap_realm(ceph_sb_to_client(ci->vfs_inode.i_sb)->mdsc, realm);
/** ci->i_head_snapc should be NULL, but we may still be waiting for a* flush_ack from the MDS. In that case, we still hold a ref for the* ceph_snap_context and we need to drop it.*/ceph_put_snap_context(ci->i_head_snapc);}
/*
This does not seem right. i_head_snapc is cleared when (ci->i_wrbuffer_ref_head == 0 && ci->i_dirty_caps == 0 && ci->i_flushing_caps == 0) . Nothing do with dropping ci->i_snap_realm. Did you see 'reconnect denied' during the test? If you did, the fix should be in iterate_session_caps()
No, I didn't saw any 'reconnect denied' in the test. The test actually seems to execute fine, except from the memory leak.
It's very difficult to reproduce this issue, but last time I managed to get this memory leak to trigger I actually had some debugging code in drop_inode_snap_realm, something like:
if (ci->i_head_snapc) printk("i_head_snapc: 0x%px\n", ci->i_head_snapc);
please add code that prints i_wrbuffer_ref_head, i_dirty_caps, i_flushing_caps. and try reproducing it again.
Ok, it took me a few hours, but I managed to reproduce the bug, with those extra printks. All those values are set to 0 when the bug triggers (and i_head_snapc != NULL).
Thanks, which test triggers this bug?
I searched that code, found we may fail to cleanup i_head_snap in two places. One is in ceph_queue_cap_snap, Another is in remove_session_caps_cb().
Cheers,
Luis
This printk was only executed when the bug triggered (during a filesystem umount) and the address shown was the same as in the kmemleak warning.
After spending some time looking, I assumed this to be a missing call to handle_cap_flush_ack, which would do the i_head_snapc cleanup.
Cheers,
Luis
"Yan, Zheng" ukernel@gmail.com writes:
On Tue, Mar 19, 2019 at 12:22 AM Luis Henriques lhenriques@suse.com wrote:
"Yan, Zheng" ukernel@gmail.com writes:
On Mon, Mar 18, 2019 at 6:33 PM Luis Henriques lhenriques@suse.com wrote:
"Yan, Zheng" ukernel@gmail.com writes:
On Fri, Mar 15, 2019 at 7:13 PM Luis Henriques lhenriques@suse.com wrote:
I'm occasionally seeing a kmemleak warning in xfstest generic/013:
unreferenced object 0xffff8881fccca940 (size 32): comm "kworker/0:1", pid 12, jiffies 4295005883 (age 130.648s) hex dump (first 32 bytes): 01 00 00 00 00 00 00 00 01 00 00 00 00 00 00 00 ................ 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ backtrace: [<00000000d741a1ea>] build_snap_context+0x5b/0x2a0 [<0000000021a00533>] rebuild_snap_realms+0x27/0x90 [<00000000ac538600>] rebuild_snap_realms+0x42/0x90 [<000000000e955fac>] ceph_update_snap_trace+0x2ee/0x610 [<00000000a9550416>] ceph_handle_snap+0x317/0x5f3 [<00000000fc287b83>] dispatch+0x362/0x176c [<00000000a312c741>] ceph_con_workfn+0x9ce/0x2cf0 [<000000004168e3a9>] process_one_work+0x1d4/0x400 [<000000002188e9e7>] worker_thread+0x2d/0x3c0 [<00000000b593e4b3>] kthread+0x112/0x130 [<00000000a8587dca>] ret_from_fork+0x35/0x40 [<00000000ba1c9c1d>] 0xffffffffffffffff
It looks like it is possible that we miss a flush_ack from the MDS when, for example, umounting the filesystem. In that case, we can simply drop the reference to the ceph_snap_context obtained in ceph_queue_cap_snap().
Link: https://tracker.ceph.com/issues/38224 Cc: stable@vger.kernel.org Signed-off-by: Luis Henriques lhenriques@suse.com
fs/ceph/caps.c | 7 +++++++ 1 file changed, 7 insertions(+)
diff --git a/fs/ceph/caps.c b/fs/ceph/caps.c index 36a8dc699448..208f4dc6f574 100644 --- a/fs/ceph/caps.c +++ b/fs/ceph/caps.c @@ -1054,6 +1054,7 @@ int ceph_is_any_caps(struct inode *inode) static void drop_inode_snap_realm(struct ceph_inode_info *ci) { struct ceph_snap_realm *realm = ci->i_snap_realm;
spin_lock(&realm->inodes_with_caps_lock); list_del_init(&ci->i_snap_realm_item); ci->i_snap_realm_counter++;@@ -1063,6 +1064,12 @@ static void drop_inode_snap_realm(struct ceph_inode_info *ci) spin_unlock(&realm->inodes_with_caps_lock); ceph_put_snap_realm(ceph_sb_to_client(ci->vfs_inode.i_sb)->mdsc, realm);
/** ci->i_head_snapc should be NULL, but we may still be waiting for a* flush_ack from the MDS. In that case, we still hold a ref for the* ceph_snap_context and we need to drop it.*/ceph_put_snap_context(ci->i_head_snapc);}
/*
This does not seem right. i_head_snapc is cleared when (ci->i_wrbuffer_ref_head == 0 && ci->i_dirty_caps == 0 && ci->i_flushing_caps == 0) . Nothing do with dropping ci->i_snap_realm. Did you see 'reconnect denied' during the test? If you did, the fix should be in iterate_session_caps()
No, I didn't saw any 'reconnect denied' in the test. The test actually seems to execute fine, except from the memory leak.
It's very difficult to reproduce this issue, but last time I managed to get this memory leak to trigger I actually had some debugging code in drop_inode_snap_realm, something like:
if (ci->i_head_snapc) printk("i_head_snapc: 0x%px\n", ci->i_head_snapc);
please add code that prints i_wrbuffer_ref_head, i_dirty_caps, i_flushing_caps. and try reproducing it again.
Ok, it took me a few hours, but I managed to reproduce the bug, with those extra printks. All those values are set to 0 when the bug triggers (and i_head_snapc != NULL).
Thanks, which test triggers this bug?
That's generic/013. It usually triggers after a few hours of running it in a loop (I'm using a vstart cluster for that).
I searched that code, found we may fail to cleanup i_head_snap in two places. One is in ceph_queue_cap_snap, Another is in remove_session_caps_cb().
Ah, great! I spent a lot of time looking but I couldn't really find it. My bet was that ceph_queue_cap_snap was doing the ceph_get_snap_context and that the corresponding ceph_put_snap_context would be done in handle_cap_flush_ack. That's why I mentioned the missing flush_ack from MDS.
Cheers,
Luis Henriques lhenriques@suse.com writes:
"Yan, Zheng" ukernel@gmail.com writes:
On Tue, Mar 19, 2019 at 12:22 AM Luis Henriques lhenriques@suse.com wrote:
"Yan, Zheng" ukernel@gmail.com writes:
On Mon, Mar 18, 2019 at 6:33 PM Luis Henriques lhenriques@suse.com wrote:
"Yan, Zheng" ukernel@gmail.com writes:
On Fri, Mar 15, 2019 at 7:13 PM Luis Henriques lhenriques@suse.com wrote: > > I'm occasionally seeing a kmemleak warning in xfstest generic/013: > > unreferenced object 0xffff8881fccca940 (size 32): > comm "kworker/0:1", pid 12, jiffies 4295005883 (age 130.648s) > hex dump (first 32 bytes): > 01 00 00 00 00 00 00 00 01 00 00 00 00 00 00 00 ................ > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ > backtrace: > [<00000000d741a1ea>] build_snap_context+0x5b/0x2a0 > [<0000000021a00533>] rebuild_snap_realms+0x27/0x90 > [<00000000ac538600>] rebuild_snap_realms+0x42/0x90 > [<000000000e955fac>] ceph_update_snap_trace+0x2ee/0x610 > [<00000000a9550416>] ceph_handle_snap+0x317/0x5f3 > [<00000000fc287b83>] dispatch+0x362/0x176c > [<00000000a312c741>] ceph_con_workfn+0x9ce/0x2cf0 > [<000000004168e3a9>] process_one_work+0x1d4/0x400 > [<000000002188e9e7>] worker_thread+0x2d/0x3c0 > [<00000000b593e4b3>] kthread+0x112/0x130 > [<00000000a8587dca>] ret_from_fork+0x35/0x40 > [<00000000ba1c9c1d>] 0xffffffffffffffff > > It looks like it is possible that we miss a flush_ack from the MDS when, > for example, umounting the filesystem. In that case, we can simply drop > the reference to the ceph_snap_context obtained in ceph_queue_cap_snap(). > > Link: https://tracker.ceph.com/issues/38224 > Cc: stable@vger.kernel.org > Signed-off-by: Luis Henriques lhenriques@suse.com > --- > fs/ceph/caps.c | 7 +++++++ > 1 file changed, 7 insertions(+) > > diff --git a/fs/ceph/caps.c b/fs/ceph/caps.c > index 36a8dc699448..208f4dc6f574 100644 > --- a/fs/ceph/caps.c > +++ b/fs/ceph/caps.c > @@ -1054,6 +1054,7 @@ int ceph_is_any_caps(struct inode *inode) > static void drop_inode_snap_realm(struct ceph_inode_info *ci) > { > struct ceph_snap_realm *realm = ci->i_snap_realm; > + > spin_lock(&realm->inodes_with_caps_lock); > list_del_init(&ci->i_snap_realm_item); > ci->i_snap_realm_counter++; > @@ -1063,6 +1064,12 @@ static void drop_inode_snap_realm(struct ceph_inode_info *ci) > spin_unlock(&realm->inodes_with_caps_lock); > ceph_put_snap_realm(ceph_sb_to_client(ci->vfs_inode.i_sb)->mdsc, > realm); > + /* > + * ci->i_head_snapc should be NULL, but we may still be waiting for a > + * flush_ack from the MDS. In that case, we still hold a ref for the > + * ceph_snap_context and we need to drop it. > + */ > + ceph_put_snap_context(ci->i_head_snapc); > } > > /*
This does not seem right. i_head_snapc is cleared when (ci->i_wrbuffer_ref_head == 0 && ci->i_dirty_caps == 0 && ci->i_flushing_caps == 0) . Nothing do with dropping ci->i_snap_realm. Did you see 'reconnect denied' during the test? If you did, the fix should be in iterate_session_caps()
No, I didn't saw any 'reconnect denied' in the test. The test actually seems to execute fine, except from the memory leak.
It's very difficult to reproduce this issue, but last time I managed to get this memory leak to trigger I actually had some debugging code in drop_inode_snap_realm, something like:
if (ci->i_head_snapc) printk("i_head_snapc: 0x%px\n", ci->i_head_snapc);
please add code that prints i_wrbuffer_ref_head, i_dirty_caps, i_flushing_caps. and try reproducing it again.
Ok, it took me a few hours, but I managed to reproduce the bug, with those extra printks. All those values are set to 0 when the bug triggers (and i_head_snapc != NULL).
Thanks, which test triggers this bug?
That's generic/013. It usually triggers after a few hours of running it in a loop (I'm using a vstart cluster for that).
I searched that code, found we may fail to cleanup i_head_snap in two places. One is in ceph_queue_cap_snap, Another is in remove_session_caps_cb().
Ah, great! I spent a lot of time looking but I couldn't really find it. My bet was that ceph_queue_cap_snap was doing the ceph_get_snap_context and that the corresponding ceph_put_snap_context would be done in handle_cap_flush_ack. That's why I mentioned the missing flush_ack from MDS.
Something that I didn't said explicitly is that I *know* that the unbalanced ceph_get_snap_context() is the one in function ceph_queue_cap_snap(). I know this for sure because I've managed to reproduce the issue several times with an instrumented kernel (with tracepoints) that allowed me to keep track of all ceph_snap_context operations (create, get, put, delete).
Cheers,
On Fri, Mar 22, 2019 at 6:04 PM Luis Henriques lhenriques@suse.com wrote:
Luis Henriques lhenriques@suse.com writes:
"Yan, Zheng" ukernel@gmail.com writes:
On Tue, Mar 19, 2019 at 12:22 AM Luis Henriques lhenriques@suse.com wrote:
"Yan, Zheng" ukernel@gmail.com writes:
On Mon, Mar 18, 2019 at 6:33 PM Luis Henriques lhenriques@suse.com wrote:
"Yan, Zheng" ukernel@gmail.com writes:
> On Fri, Mar 15, 2019 at 7:13 PM Luis Henriques lhenriques@suse.com wrote: >> >> I'm occasionally seeing a kmemleak warning in xfstest generic/013: >> >> unreferenced object 0xffff8881fccca940 (size 32): >> comm "kworker/0:1", pid 12, jiffies 4295005883 (age 130.648s) >> hex dump (first 32 bytes): >> 01 00 00 00 00 00 00 00 01 00 00 00 00 00 00 00 ................ >> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ >> backtrace: >> [<00000000d741a1ea>] build_snap_context+0x5b/0x2a0 >> [<0000000021a00533>] rebuild_snap_realms+0x27/0x90 >> [<00000000ac538600>] rebuild_snap_realms+0x42/0x90 >> [<000000000e955fac>] ceph_update_snap_trace+0x2ee/0x610 >> [<00000000a9550416>] ceph_handle_snap+0x317/0x5f3 >> [<00000000fc287b83>] dispatch+0x362/0x176c >> [<00000000a312c741>] ceph_con_workfn+0x9ce/0x2cf0 >> [<000000004168e3a9>] process_one_work+0x1d4/0x400 >> [<000000002188e9e7>] worker_thread+0x2d/0x3c0 >> [<00000000b593e4b3>] kthread+0x112/0x130 >> [<00000000a8587dca>] ret_from_fork+0x35/0x40 >> [<00000000ba1c9c1d>] 0xffffffffffffffff >> >> It looks like it is possible that we miss a flush_ack from the MDS when, >> for example, umounting the filesystem. In that case, we can simply drop >> the reference to the ceph_snap_context obtained in ceph_queue_cap_snap(). >> >> Link: https://tracker.ceph.com/issues/38224 >> Cc: stable@vger.kernel.org >> Signed-off-by: Luis Henriques lhenriques@suse.com >> --- >> fs/ceph/caps.c | 7 +++++++ >> 1 file changed, 7 insertions(+) >> >> diff --git a/fs/ceph/caps.c b/fs/ceph/caps.c >> index 36a8dc699448..208f4dc6f574 100644 >> --- a/fs/ceph/caps.c >> +++ b/fs/ceph/caps.c >> @@ -1054,6 +1054,7 @@ int ceph_is_any_caps(struct inode *inode) >> static void drop_inode_snap_realm(struct ceph_inode_info *ci) >> { >> struct ceph_snap_realm *realm = ci->i_snap_realm; >> + >> spin_lock(&realm->inodes_with_caps_lock); >> list_del_init(&ci->i_snap_realm_item); >> ci->i_snap_realm_counter++; >> @@ -1063,6 +1064,12 @@ static void drop_inode_snap_realm(struct ceph_inode_info *ci) >> spin_unlock(&realm->inodes_with_caps_lock); >> ceph_put_snap_realm(ceph_sb_to_client(ci->vfs_inode.i_sb)->mdsc, >> realm); >> + /* >> + * ci->i_head_snapc should be NULL, but we may still be waiting for a >> + * flush_ack from the MDS. In that case, we still hold a ref for the >> + * ceph_snap_context and we need to drop it. >> + */ >> + ceph_put_snap_context(ci->i_head_snapc); >> } >> >> /* > > This does not seem right. i_head_snapc is cleared when > (ci->i_wrbuffer_ref_head == 0 && ci->i_dirty_caps == 0 && > ci->i_flushing_caps == 0) . Nothing do with dropping ci->i_snap_realm. > Did you see 'reconnect denied' during the test? If you did, the fix > should be in iterate_session_caps() >
No, I didn't saw any 'reconnect denied' in the test. The test actually seems to execute fine, except from the memory leak.
It's very difficult to reproduce this issue, but last time I managed to get this memory leak to trigger I actually had some debugging code in drop_inode_snap_realm, something like:
if (ci->i_head_snapc) printk("i_head_snapc: 0x%px\n", ci->i_head_snapc);
please add code that prints i_wrbuffer_ref_head, i_dirty_caps, i_flushing_caps. and try reproducing it again.
Ok, it took me a few hours, but I managed to reproduce the bug, with those extra printks. All those values are set to 0 when the bug triggers (and i_head_snapc != NULL).
Thanks, which test triggers this bug?
That's generic/013. It usually triggers after a few hours of running it in a loop (I'm using a vstart cluster for that).
I searched that code, found we may fail to cleanup i_head_snap in two places. One is in ceph_queue_cap_snap, Another is in remove_session_caps_cb().
Ah, great! I spent a lot of time looking but I couldn't really find it. My bet was that ceph_queue_cap_snap was doing the ceph_get_snap_context and that the corresponding ceph_put_snap_context would be done in handle_cap_flush_ack. That's why I mentioned the missing flush_ack from MDS.
Something that I didn't said explicitly is that I *know* that the unbalanced ceph_get_snap_context() is the one in function ceph_queue_cap_snap(). I know this for sure because I've managed to reproduce the issue several times with an instrumented kernel (with tracepoints) that allowed me to keep track of all ceph_snap_context operations (create, get, put, delete).
Sorry for the delay. please try
diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c index 45f061e47721..5bc30e0d252a 100644 --- a/fs/ceph/mds_client.c +++ b/fs/ceph/mds_client.c @@ -1420,6 +1420,15 @@ static int remove_session_caps_cb(struct inode *inode, struct ceph_cap *cap, list_add(&ci->i_prealloc_cap_flush->i_list, &to_remove); ci->i_prealloc_cap_flush = NULL; } + + if (drop && + ci->i_wrbuffer_ref_head == 0 && + ci->i_wr_ref == 0 && + ci->i_dirty_caps == 0 && + ci->i_flushing_caps == 0) { + ceph_put_snap_context(ci->i_head_snapc); + ci->i_head_snapc = NULL; + } } spin_unlock(&ci->i_ceph_lock); while (!list_empty(&to_remove)) { diff --git a/fs/ceph/snap.c b/fs/ceph/snap.c index 89aa37fa0f84..0af4b3d32122 100644 --- a/fs/ceph/snap.c +++ b/fs/ceph/snap.c @@ -572,7 +572,12 @@ void ceph_queue_cap_snap(struct ceph_inode_info *ci) old_snapc = NULL;
update_snapc: - if (ci->i_head_snapc) { + if (ci->i_wrbuffer_ref_head == 0 && + ci->i_wr_ref == 0 && + ci->i_dirty_caps == 0 && + ci->i_flushing_caps == 0) { + ci->i_head_snapc = NULL; + } else { ci->i_head_snapc = ceph_get_snap_context(new_snapc); dout(" new snapc is %p\n", new_snapc); }
Cheers,
Luis
"Yan, Zheng" ukernel@gmail.com writes:
On Fri, Mar 22, 2019 at 6:04 PM Luis Henriques lhenriques@suse.com wrote:
Luis Henriques lhenriques@suse.com writes:
"Yan, Zheng" ukernel@gmail.com writes:
On Tue, Mar 19, 2019 at 12:22 AM Luis Henriques lhenriques@suse.com wrote:
"Yan, Zheng" ukernel@gmail.com writes:
On Mon, Mar 18, 2019 at 6:33 PM Luis Henriques lhenriques@suse.com wrote: > > "Yan, Zheng" ukernel@gmail.com writes: > > > On Fri, Mar 15, 2019 at 7:13 PM Luis Henriques lhenriques@suse.com wrote: > >> > >> I'm occasionally seeing a kmemleak warning in xfstest generic/013: > >> > >> unreferenced object 0xffff8881fccca940 (size 32): > >> comm "kworker/0:1", pid 12, jiffies 4295005883 (age 130.648s) > >> hex dump (first 32 bytes): > >> 01 00 00 00 00 00 00 00 01 00 00 00 00 00 00 00 ................ > >> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ > >> backtrace: > >> [<00000000d741a1ea>] build_snap_context+0x5b/0x2a0 > >> [<0000000021a00533>] rebuild_snap_realms+0x27/0x90 > >> [<00000000ac538600>] rebuild_snap_realms+0x42/0x90 > >> [<000000000e955fac>] ceph_update_snap_trace+0x2ee/0x610 > >> [<00000000a9550416>] ceph_handle_snap+0x317/0x5f3 > >> [<00000000fc287b83>] dispatch+0x362/0x176c > >> [<00000000a312c741>] ceph_con_workfn+0x9ce/0x2cf0 > >> [<000000004168e3a9>] process_one_work+0x1d4/0x400 > >> [<000000002188e9e7>] worker_thread+0x2d/0x3c0 > >> [<00000000b593e4b3>] kthread+0x112/0x130 > >> [<00000000a8587dca>] ret_from_fork+0x35/0x40 > >> [<00000000ba1c9c1d>] 0xffffffffffffffff > >> > >> It looks like it is possible that we miss a flush_ack from the MDS when, > >> for example, umounting the filesystem. In that case, we can simply drop > >> the reference to the ceph_snap_context obtained in ceph_queue_cap_snap(). > >> > >> Link: https://tracker.ceph.com/issues/38224 > >> Cc: stable@vger.kernel.org > >> Signed-off-by: Luis Henriques lhenriques@suse.com > >> --- > >> fs/ceph/caps.c | 7 +++++++ > >> 1 file changed, 7 insertions(+) > >> > >> diff --git a/fs/ceph/caps.c b/fs/ceph/caps.c > >> index 36a8dc699448..208f4dc6f574 100644 > >> --- a/fs/ceph/caps.c > >> +++ b/fs/ceph/caps.c > >> @@ -1054,6 +1054,7 @@ int ceph_is_any_caps(struct inode *inode) > >> static void drop_inode_snap_realm(struct ceph_inode_info *ci) > >> { > >> struct ceph_snap_realm *realm = ci->i_snap_realm; > >> + > >> spin_lock(&realm->inodes_with_caps_lock); > >> list_del_init(&ci->i_snap_realm_item); > >> ci->i_snap_realm_counter++; > >> @@ -1063,6 +1064,12 @@ static void drop_inode_snap_realm(struct ceph_inode_info *ci) > >> spin_unlock(&realm->inodes_with_caps_lock); > >> ceph_put_snap_realm(ceph_sb_to_client(ci->vfs_inode.i_sb)->mdsc, > >> realm); > >> + /* > >> + * ci->i_head_snapc should be NULL, but we may still be waiting for a > >> + * flush_ack from the MDS. In that case, we still hold a ref for the > >> + * ceph_snap_context and we need to drop it. > >> + */ > >> + ceph_put_snap_context(ci->i_head_snapc); > >> } > >> > >> /* > > > > This does not seem right. i_head_snapc is cleared when > > (ci->i_wrbuffer_ref_head == 0 && ci->i_dirty_caps == 0 && > > ci->i_flushing_caps == 0) . Nothing do with dropping ci->i_snap_realm. > > Did you see 'reconnect denied' during the test? If you did, the fix > > should be in iterate_session_caps() > > > > No, I didn't saw any 'reconnect denied' in the test. The test actually > seems to execute fine, except from the memory leak. > > It's very difficult to reproduce this issue, but last time I managed to > get this memory leak to trigger I actually had some debugging code in > drop_inode_snap_realm, something like: > > if (ci->i_head_snapc) > printk("i_head_snapc: 0x%px\n", ci->i_head_snapc);
please add code that prints i_wrbuffer_ref_head, i_dirty_caps, i_flushing_caps. and try reproducing it again.
Ok, it took me a few hours, but I managed to reproduce the bug, with those extra printks. All those values are set to 0 when the bug triggers (and i_head_snapc != NULL).
Thanks, which test triggers this bug?
That's generic/013. It usually triggers after a few hours of running it in a loop (I'm using a vstart cluster for that).
I searched that code, found we may fail to cleanup i_head_snap in two places. One is in ceph_queue_cap_snap, Another is in remove_session_caps_cb().
Ah, great! I spent a lot of time looking but I couldn't really find it. My bet was that ceph_queue_cap_snap was doing the ceph_get_snap_context and that the corresponding ceph_put_snap_context would be done in handle_cap_flush_ack. That's why I mentioned the missing flush_ack from MDS.
Something that I didn't said explicitly is that I *know* that the unbalanced ceph_get_snap_context() is the one in function ceph_queue_cap_snap(). I know this for sure because I've managed to reproduce the issue several times with an instrumented kernel (with tracepoints) that allowed me to keep track of all ceph_snap_context operations (create, get, put, delete).
Sorry for the delay. please try
Thank you, I'll try the test with your patch applied and see if I still see the issue (obviously, this will take some time as it takes several hours for the bug to trigger).
Cheers,
Luis Henriques lhenriques@suse.com writes:
"Yan, Zheng" ukernel@gmail.com writes:
On Fri, Mar 22, 2019 at 6:04 PM Luis Henriques lhenriques@suse.com wrote:
Luis Henriques lhenriques@suse.com writes:
"Yan, Zheng" ukernel@gmail.com writes:
On Tue, Mar 19, 2019 at 12:22 AM Luis Henriques lhenriques@suse.com wrote:
"Yan, Zheng" ukernel@gmail.com writes:
> On Mon, Mar 18, 2019 at 6:33 PM Luis Henriques lhenriques@suse.com wrote: >> >> "Yan, Zheng" ukernel@gmail.com writes: >> >> > On Fri, Mar 15, 2019 at 7:13 PM Luis Henriques lhenriques@suse.com wrote: >> >> >> >> I'm occasionally seeing a kmemleak warning in xfstest generic/013: >> >> >> >> unreferenced object 0xffff8881fccca940 (size 32): >> >> comm "kworker/0:1", pid 12, jiffies 4295005883 (age 130.648s) >> >> hex dump (first 32 bytes): >> >> 01 00 00 00 00 00 00 00 01 00 00 00 00 00 00 00 ................ >> >> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ >> >> backtrace: >> >> [<00000000d741a1ea>] build_snap_context+0x5b/0x2a0 >> >> [<0000000021a00533>] rebuild_snap_realms+0x27/0x90 >> >> [<00000000ac538600>] rebuild_snap_realms+0x42/0x90 >> >> [<000000000e955fac>] ceph_update_snap_trace+0x2ee/0x610 >> >> [<00000000a9550416>] ceph_handle_snap+0x317/0x5f3 >> >> [<00000000fc287b83>] dispatch+0x362/0x176c >> >> [<00000000a312c741>] ceph_con_workfn+0x9ce/0x2cf0 >> >> [<000000004168e3a9>] process_one_work+0x1d4/0x400 >> >> [<000000002188e9e7>] worker_thread+0x2d/0x3c0 >> >> [<00000000b593e4b3>] kthread+0x112/0x130 >> >> [<00000000a8587dca>] ret_from_fork+0x35/0x40 >> >> [<00000000ba1c9c1d>] 0xffffffffffffffff >> >> >> >> It looks like it is possible that we miss a flush_ack from the MDS when, >> >> for example, umounting the filesystem. In that case, we can simply drop >> >> the reference to the ceph_snap_context obtained in ceph_queue_cap_snap(). >> >> >> >> Link: https://tracker.ceph.com/issues/38224 >> >> Cc: stable@vger.kernel.org >> >> Signed-off-by: Luis Henriques lhenriques@suse.com >> >> --- >> >> fs/ceph/caps.c | 7 +++++++ >> >> 1 file changed, 7 insertions(+) >> >> >> >> diff --git a/fs/ceph/caps.c b/fs/ceph/caps.c >> >> index 36a8dc699448..208f4dc6f574 100644 >> >> --- a/fs/ceph/caps.c >> >> +++ b/fs/ceph/caps.c >> >> @@ -1054,6 +1054,7 @@ int ceph_is_any_caps(struct inode *inode) >> >> static void drop_inode_snap_realm(struct ceph_inode_info *ci) >> >> { >> >> struct ceph_snap_realm *realm = ci->i_snap_realm; >> >> + >> >> spin_lock(&realm->inodes_with_caps_lock); >> >> list_del_init(&ci->i_snap_realm_item); >> >> ci->i_snap_realm_counter++; >> >> @@ -1063,6 +1064,12 @@ static void drop_inode_snap_realm(struct ceph_inode_info *ci) >> >> spin_unlock(&realm->inodes_with_caps_lock); >> >> ceph_put_snap_realm(ceph_sb_to_client(ci->vfs_inode.i_sb)->mdsc, >> >> realm); >> >> + /* >> >> + * ci->i_head_snapc should be NULL, but we may still be waiting for a >> >> + * flush_ack from the MDS. In that case, we still hold a ref for the >> >> + * ceph_snap_context and we need to drop it. >> >> + */ >> >> + ceph_put_snap_context(ci->i_head_snapc); >> >> } >> >> >> >> /* >> > >> > This does not seem right. i_head_snapc is cleared when >> > (ci->i_wrbuffer_ref_head == 0 && ci->i_dirty_caps == 0 && >> > ci->i_flushing_caps == 0) . Nothing do with dropping ci->i_snap_realm. >> > Did you see 'reconnect denied' during the test? If you did, the fix >> > should be in iterate_session_caps() >> > >> >> No, I didn't saw any 'reconnect denied' in the test. The test actually >> seems to execute fine, except from the memory leak. >> >> It's very difficult to reproduce this issue, but last time I managed to >> get this memory leak to trigger I actually had some debugging code in >> drop_inode_snap_realm, something like: >> >> if (ci->i_head_snapc) >> printk("i_head_snapc: 0x%px\n", ci->i_head_snapc); > > please add code that prints i_wrbuffer_ref_head, i_dirty_caps, > i_flushing_caps. and try reproducing it again. >
Ok, it took me a few hours, but I managed to reproduce the bug, with those extra printks. All those values are set to 0 when the bug triggers (and i_head_snapc != NULL).
Thanks, which test triggers this bug?
That's generic/013. It usually triggers after a few hours of running it in a loop (I'm using a vstart cluster for that).
I searched that code, found we may fail to cleanup i_head_snap in two places. One is in ceph_queue_cap_snap, Another is in remove_session_caps_cb().
Ah, great! I spent a lot of time looking but I couldn't really find it. My bet was that ceph_queue_cap_snap was doing the ceph_get_snap_context and that the corresponding ceph_put_snap_context would be done in handle_cap_flush_ack. That's why I mentioned the missing flush_ack from MDS.
Something that I didn't said explicitly is that I *know* that the unbalanced ceph_get_snap_context() is the one in function ceph_queue_cap_snap(). I know this for sure because I've managed to reproduce the issue several times with an instrumented kernel (with tracepoints) that allowed me to keep track of all ceph_snap_context operations (create, get, put, delete).
Sorry for the delay. please try
Thank you, I'll try the test with your patch applied and see if I still see the issue (obviously, this will take some time as it takes several hours for the bug to trigger).
Ok, after several hours of running it, I confirm that I was not able to reproduce the issue with your patch. It took me a while because my test environment changed a bit and I was failing to reproduce it even without the patch.
Cheers,
On Tue, Apr 16, 2019 at 9:30 PM Luis Henriques lhenriques@suse.com wrote:
Luis Henriques lhenriques@suse.com writes:
"Yan, Zheng" ukernel@gmail.com writes:
On Fri, Mar 22, 2019 at 6:04 PM Luis Henriques lhenriques@suse.com wrote:
Luis Henriques lhenriques@suse.com writes:
"Yan, Zheng" ukernel@gmail.com writes:
On Tue, Mar 19, 2019 at 12:22 AM Luis Henriques lhenriques@suse.com wrote: > > "Yan, Zheng" ukernel@gmail.com writes: > > > On Mon, Mar 18, 2019 at 6:33 PM Luis Henriques lhenriques@suse.com wrote: > >> > >> "Yan, Zheng" ukernel@gmail.com writes: > >> > >> > On Fri, Mar 15, 2019 at 7:13 PM Luis Henriques lhenriques@suse.com wrote: > >> >> > >> >> I'm occasionally seeing a kmemleak warning in xfstest generic/013: > >> >> > >> >> unreferenced object 0xffff8881fccca940 (size 32): > >> >> comm "kworker/0:1", pid 12, jiffies 4295005883 (age 130.648s) > >> >> hex dump (first 32 bytes): > >> >> 01 00 00 00 00 00 00 00 01 00 00 00 00 00 00 00 ................ > >> >> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ > >> >> backtrace: > >> >> [<00000000d741a1ea>] build_snap_context+0x5b/0x2a0 > >> >> [<0000000021a00533>] rebuild_snap_realms+0x27/0x90 > >> >> [<00000000ac538600>] rebuild_snap_realms+0x42/0x90 > >> >> [<000000000e955fac>] ceph_update_snap_trace+0x2ee/0x610 > >> >> [<00000000a9550416>] ceph_handle_snap+0x317/0x5f3 > >> >> [<00000000fc287b83>] dispatch+0x362/0x176c > >> >> [<00000000a312c741>] ceph_con_workfn+0x9ce/0x2cf0 > >> >> [<000000004168e3a9>] process_one_work+0x1d4/0x400 > >> >> [<000000002188e9e7>] worker_thread+0x2d/0x3c0 > >> >> [<00000000b593e4b3>] kthread+0x112/0x130 > >> >> [<00000000a8587dca>] ret_from_fork+0x35/0x40 > >> >> [<00000000ba1c9c1d>] 0xffffffffffffffff > >> >> > >> >> It looks like it is possible that we miss a flush_ack from the MDS when, > >> >> for example, umounting the filesystem. In that case, we can simply drop > >> >> the reference to the ceph_snap_context obtained in ceph_queue_cap_snap(). > >> >> > >> >> Link: https://tracker.ceph.com/issues/38224 > >> >> Cc: stable@vger.kernel.org > >> >> Signed-off-by: Luis Henriques lhenriques@suse.com > >> >> --- > >> >> fs/ceph/caps.c | 7 +++++++ > >> >> 1 file changed, 7 insertions(+) > >> >> > >> >> diff --git a/fs/ceph/caps.c b/fs/ceph/caps.c > >> >> index 36a8dc699448..208f4dc6f574 100644 > >> >> --- a/fs/ceph/caps.c > >> >> +++ b/fs/ceph/caps.c > >> >> @@ -1054,6 +1054,7 @@ int ceph_is_any_caps(struct inode *inode) > >> >> static void drop_inode_snap_realm(struct ceph_inode_info *ci) > >> >> { > >> >> struct ceph_snap_realm *realm = ci->i_snap_realm; > >> >> + > >> >> spin_lock(&realm->inodes_with_caps_lock); > >> >> list_del_init(&ci->i_snap_realm_item); > >> >> ci->i_snap_realm_counter++; > >> >> @@ -1063,6 +1064,12 @@ static void drop_inode_snap_realm(struct ceph_inode_info *ci) > >> >> spin_unlock(&realm->inodes_with_caps_lock); > >> >> ceph_put_snap_realm(ceph_sb_to_client(ci->vfs_inode.i_sb)->mdsc, > >> >> realm); > >> >> + /* > >> >> + * ci->i_head_snapc should be NULL, but we may still be waiting for a > >> >> + * flush_ack from the MDS. In that case, we still hold a ref for the > >> >> + * ceph_snap_context and we need to drop it. > >> >> + */ > >> >> + ceph_put_snap_context(ci->i_head_snapc); > >> >> } > >> >> > >> >> /* > >> > > >> > This does not seem right. i_head_snapc is cleared when > >> > (ci->i_wrbuffer_ref_head == 0 && ci->i_dirty_caps == 0 && > >> > ci->i_flushing_caps == 0) . Nothing do with dropping ci->i_snap_realm. > >> > Did you see 'reconnect denied' during the test? If you did, the fix > >> > should be in iterate_session_caps() > >> > > >> > >> No, I didn't saw any 'reconnect denied' in the test. The test actually > >> seems to execute fine, except from the memory leak. > >> > >> It's very difficult to reproduce this issue, but last time I managed to > >> get this memory leak to trigger I actually had some debugging code in > >> drop_inode_snap_realm, something like: > >> > >> if (ci->i_head_snapc) > >> printk("i_head_snapc: 0x%px\n", ci->i_head_snapc); > > > > please add code that prints i_wrbuffer_ref_head, i_dirty_caps, > > i_flushing_caps. and try reproducing it again. > > > > Ok, it took me a few hours, but I managed to reproduce the bug, with > those extra printks. All those values are set to 0 when the bug > triggers (and i_head_snapc != NULL). >
Thanks, which test triggers this bug?
That's generic/013. It usually triggers after a few hours of running it in a loop (I'm using a vstart cluster for that).
I searched that code, found we may fail to cleanup i_head_snap in two places. One is in ceph_queue_cap_snap, Another is in remove_session_caps_cb().
Ah, great! I spent a lot of time looking but I couldn't really find it. My bet was that ceph_queue_cap_snap was doing the ceph_get_snap_context and that the corresponding ceph_put_snap_context would be done in handle_cap_flush_ack. That's why I mentioned the missing flush_ack from MDS.
Something that I didn't said explicitly is that I *know* that the unbalanced ceph_get_snap_context() is the one in function ceph_queue_cap_snap(). I know this for sure because I've managed to reproduce the issue several times with an instrumented kernel (with tracepoints) that allowed me to keep track of all ceph_snap_context operations (create, get, put, delete).
Sorry for the delay. please try
Thank you, I'll try the test with your patch applied and see if I still see the issue (obviously, this will take some time as it takes several hours for the bug to trigger).
Ok, after several hours of running it, I confirm that I was not able to reproduce the issue with your patch. It took me a while because my test environment changed a bit and I was failing to reproduce it even without the patch.
Thanks, I pushed the patch to testing branch.
Yan, Zheng
Cheers,
Luis
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Luis Henriques -
Yan, Zheng