From: Jaegeuk Kim jaegeuk@kernel.org
[ Upstream commit a1933c09ef84c2fd187e05b560ddc6e1267d6508 ]
[ 155.018460] ====================================================== [ 155.021431] WARNING: possible circular locking dependency detected [ 155.024339] 4.18.0-rc3+ #5 Tainted: G OE [ 155.026879] ------------------------------------------------------ [ 155.029783] umount/2901 is trying to acquire lock: [ 155.032187] 00000000c4282f1f (kn->count#130){++++}, at: kernfs_remove+0x1f/0x30 [ 155.035439] [ 155.035439] but task is already holding lock: [ 155.038892] 0000000056e4307b (&type->s_umount_key#41){++++}, at: deactivate_super+0x33/0x50 [ 155.042602] [ 155.042602] which lock already depends on the new lock. [ 155.042602] [ 155.047465] [ 155.047465] the existing dependency chain (in reverse order) is: [ 155.051354] [ 155.051354] -> #1 (&type->s_umount_key#41){++++}: [ 155.054768] f2fs_sbi_store+0x61/0x460 [f2fs] [ 155.057083] kernfs_fop_write+0x113/0x1a0 [ 155.059277] __vfs_write+0x36/0x180 [ 155.061250] vfs_write+0xbe/0x1b0 [ 155.063179] ksys_write+0x55/0xc0 [ 155.065068] do_syscall_64+0x60/0x1b0 [ 155.067071] entry_SYSCALL_64_after_hwframe+0x49/0xbe [ 155.069529] [ 155.069529] -> #0 (kn->count#130){++++}: [ 155.072421] __kernfs_remove+0x26f/0x2e0 [ 155.074452] kernfs_remove+0x1f/0x30 [ 155.076342] kobject_del.part.5+0xe/0x40 [ 155.078354] f2fs_put_super+0x12d/0x290 [f2fs] [ 155.080500] generic_shutdown_super+0x6c/0x110 [ 155.082655] kill_block_super+0x21/0x50 [ 155.084634] kill_f2fs_super+0x9c/0xc0 [f2fs] [ 155.086726] deactivate_locked_super+0x3f/0x70 [ 155.088826] cleanup_mnt+0x3b/0x70 [ 155.090584] task_work_run+0x93/0xc0 [ 155.092367] exit_to_usermode_loop+0xf0/0x100 [ 155.094466] do_syscall_64+0x162/0x1b0 [ 155.096312] entry_SYSCALL_64_after_hwframe+0x49/0xbe [ 155.098603] [ 155.098603] other info that might help us debug this: [ 155.098603] [ 155.102418] Possible unsafe locking scenario: [ 155.102418] [ 155.105134] CPU0 CPU1 [ 155.107037] ---- ---- [ 155.108910] lock(&type->s_umount_key#41); [ 155.110674] lock(kn->count#130); [ 155.113010] lock(&type->s_umount_key#41); [ 155.115608] lock(kn->count#130);
Reviewed-by: Chao Yu yuchao0@huawei.com Signed-off-by: Jaegeuk Kim jaegeuk@kernel.org Signed-off-by: Sasha Levin alexander.levin@microsoft.com --- fs/f2fs/sysfs.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/fs/f2fs/sysfs.c b/fs/f2fs/sysfs.c index 5344e21853b2..bca1236fd6fa 100644 --- a/fs/f2fs/sysfs.c +++ b/fs/f2fs/sysfs.c @@ -287,8 +287,10 @@ static ssize_t f2fs_sbi_store(struct f2fs_attr *a, bool gc_entry = (!strcmp(a->attr.name, "gc_urgent") || a->struct_type == GC_THREAD);
- if (gc_entry) - down_read(&sbi->sb->s_umount); + if (gc_entry) { + if (!down_read_trylock(&sbi->sb->s_umount)) + return -EAGAIN; + } ret = __sbi_store(a, sbi, buf, count); if (gc_entry) up_read(&sbi->sb->s_umount);