| Message ID | 5dccee8f9d7fe7b5072090327854fcbfdbd45b28.1598996236.git.josef@toxicpanda.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Lockdep fixes | expand |
On 2/9/20 5:40 am, Josef Bacik wrote: > While running btrfs/187 I hit the following lockdep splat > > ====================================================== > WARNING: possible circular locking dependency detected > 5.9.0-rc3+ #4 Not tainted > ------------------------------------------------------ > kswapd0/100 is trying to acquire lock: > ffff96ecc22ef4a0 (&delayed_node->mutex){+.+.}-{3:3}, at: __btrfs_release_delayed_node.part.0+0x3f/0x330 > > but task is already holding lock: > ffffffff8dd74700 (fs_reclaim){+.+.}-{0:0}, at: __fs_reclaim_acquire+0x5/0x30 > > which lock already depends on the new lock. > > the existing dependency chain (in reverse order) is: > > -> #3 (fs_reclaim){+.+.}-{0:0}: > fs_reclaim_acquire+0x65/0x80 > slab_pre_alloc_hook.constprop.0+0x20/0x200 > kmem_cache_alloc+0x37/0x270 > alloc_inode+0x82/0xb0 > iget_locked+0x10d/0x2c0 > kernfs_get_inode+0x1b/0x130 > kernfs_get_tree+0x136/0x240 > sysfs_get_tree+0x16/0x40 > vfs_get_tree+0x28/0xc0 > path_mount+0x434/0xc00 > __x64_sys_mount+0xe3/0x120 > do_syscall_64+0x33/0x40 > entry_SYSCALL_64_after_hwframe+0x44/0xa9 > > -> #2 (kernfs_mutex){+.+.}-{3:3}: > __mutex_lock+0x7e/0x7e0 > kernfs_add_one+0x23/0x150 > kernfs_create_link+0x63/0xa0 > sysfs_do_create_link_sd+0x5e/0xd0 > btrfs_sysfs_add_devices_dir+0x81/0x130 > btrfs_init_new_device+0x67f/0x1250 > btrfs_ioctl+0x1ef/0x2e20 > __x64_sys_ioctl+0x83/0xb0 > do_syscall_64+0x33/0x40 > entry_SYSCALL_64_after_hwframe+0x44/0xa9 > > -> #1 (&fs_info->chunk_mutex){+.+.}-{3:3}: > __mutex_lock+0x7e/0x7e0 > btrfs_chunk_alloc+0x125/0x3a0 > find_free_extent+0xdf6/0x1210 > btrfs_reserve_extent+0xb3/0x1b0 > btrfs_alloc_tree_block+0xb0/0x310 > alloc_tree_block_no_bg_flush+0x4a/0x60 > __btrfs_cow_block+0x11a/0x530 > btrfs_cow_block+0x104/0x220 > btrfs_search_slot+0x52e/0x9d0 > btrfs_insert_empty_items+0x64/0xb0 > btrfs_insert_delayed_items+0x90/0x4f0 > btrfs_commit_inode_delayed_items+0x93/0x140 > btrfs_log_inode+0x5de/0x2020 > btrfs_log_inode_parent+0x429/0xc90 > btrfs_log_new_name+0x95/0x9b > btrfs_rename2+0xbb9/0x1800 > vfs_rename+0x64f/0x9f0 > do_renameat2+0x320/0x4e0 > __x64_sys_rename+0x1f/0x30 > do_syscall_64+0x33/0x40 > entry_SYSCALL_64_after_hwframe+0x44/0xa9 > > -> #0 (&delayed_node->mutex){+.+.}-{3:3}: > __lock_acquire+0x119c/0x1fc0 > lock_acquire+0xa7/0x3d0 > __mutex_lock+0x7e/0x7e0 > __btrfs_release_delayed_node.part.0+0x3f/0x330 > btrfs_evict_inode+0x24c/0x500 > evict+0xcf/0x1f0 > dispose_list+0x48/0x70 > prune_icache_sb+0x44/0x50 > super_cache_scan+0x161/0x1e0 > do_shrink_slab+0x178/0x3c0 > shrink_slab+0x17c/0x290 > shrink_node+0x2b2/0x6d0 > balance_pgdat+0x30a/0x670 > kswapd+0x213/0x4c0 > kthread+0x138/0x160 > ret_from_fork+0x1f/0x30 > > other info that might help us debug this: > > Chain exists of: > &delayed_node->mutex --> kernfs_mutex --> fs_reclaim > > Possible unsafe locking scenario: > > CPU0 CPU1 > ---- ---- > lock(fs_reclaim); > lock(kernfs_mutex); > lock(fs_reclaim); > lock(&delayed_node->mutex); > > *** DEADLOCK *** > > 3 locks held by kswapd0/100: > #0: ffffffff8dd74700 (fs_reclaim){+.+.}-{0:0}, at: __fs_reclaim_acquire+0x5/0x30 > #1: ffffffff8dd65c50 (shrinker_rwsem){++++}-{3:3}, at: shrink_slab+0x115/0x290 > #2: ffff96ed2ade30e0 (&type->s_umount_key#36){++++}-{3:3}, at: super_cache_scan+0x38/0x1e0 > > stack backtrace: > CPU: 0 PID: 100 Comm: kswapd0 Not tainted 5.9.0-rc3+ #4 > Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.13.0-2.fc32 04/01/2014 > Call Trace: > dump_stack+0x8b/0xb8 > check_noncircular+0x12d/0x150 > __lock_acquire+0x119c/0x1fc0 > lock_acquire+0xa7/0x3d0 > ? __btrfs_release_delayed_node.part.0+0x3f/0x330 > __mutex_lock+0x7e/0x7e0 > ? __btrfs_release_delayed_node.part.0+0x3f/0x330 > ? __btrfs_release_delayed_node.part.0+0x3f/0x330 > ? lock_acquire+0xa7/0x3d0 > ? find_held_lock+0x2b/0x80 > __btrfs_release_delayed_node.part.0+0x3f/0x330 > btrfs_evict_inode+0x24c/0x500 > evict+0xcf/0x1f0 > dispose_list+0x48/0x70 > prune_icache_sb+0x44/0x50 > super_cache_scan+0x161/0x1e0 > do_shrink_slab+0x178/0x3c0 > shrink_slab+0x17c/0x290 > shrink_node+0x2b2/0x6d0 > balance_pgdat+0x30a/0x670 > kswapd+0x213/0x4c0 > ? _raw_spin_unlock_irqrestore+0x41/0x50 > ? add_wait_queue_exclusive+0x70/0x70 > ? balance_pgdat+0x670/0x670 > kthread+0x138/0x160 > ? kthread_create_worker_on_cpu+0x40/0x40 > ret_from_fork+0x1f/0x30 > > This happens because we are holding the chunk_mutex at the time of > adding in a new device. However we only need to hold the > device_list_mutex, as we're going to iterate over the fs_devices > devices. Move the sysfs init stuff outside of the chunk_mutex to get > rid of this lockdep splat. > > Signed-off-by: Josef Bacik <josef@toxicpanda.com> > > --- > fs/btrfs/volumes.c | 7 ++++--- > 1 file changed, 4 insertions(+), 3 deletions(-) > > diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c > index d6bbbe1986bb..77b7da42c651 100644 > --- a/fs/btrfs/volumes.c > +++ b/fs/btrfs/volumes.c > @@ -2599,9 +2599,6 @@ int btrfs_init_new_device(struct btrfs_fs_info *fs_info, const char *device_path > btrfs_set_super_num_devices(fs_info->super_copy, > orig_super_num_devices + 1); > > - /* add sysfs device entry */ > - btrfs_sysfs_add_devices_dir(fs_devices, device); > - > /* > * we've got more storage, clear any full flags on the space > * infos > @@ -2609,6 +2606,10 @@ int btrfs_init_new_device(struct btrfs_fs_info *fs_info, const char *device_path > btrfs_clear_space_info_full(fs_info); > > mutex_unlock(&fs_info->chunk_mutex); > + > + /* add sysfs device entry */ > + btrfs_sysfs_add_devices_dir(fs_devices, device); > + > mutex_unlock(&fs_devices->device_list_mutex); > > if (seeding_dev) { > Strange we should get this splat when btrfs_sysfs_add_devices_dir() already has implicit GFP_NOFS allocation scope right? What did I miss? Thanks, Anand
On Wed, Sep 02, 2020 at 02:21:31PM +0800, Anand Jain wrote: > > @@ -2609,6 +2606,10 @@ int btrfs_init_new_device(struct btrfs_fs_info *fs_info, const char *device_path > > btrfs_clear_space_info_full(fs_info); > > > > mutex_unlock(&fs_info->chunk_mutex); > > + > > + /* add sysfs device entry */ > > + btrfs_sysfs_add_devices_dir(fs_devices, device); > > + > > mutex_unlock(&fs_devices->device_list_mutex); > > > > if (seeding_dev) { > > > > Strange we should get this splat when btrfs_sysfs_add_devices_dir() > already has implicit GFP_NOFS allocation scope right? What did I > miss? The problem is the sysfs' kernfs_mutex, all sysfs allocations are GFP_KERNEL thus it can grab fs_reclaim at some point.
On Tue, Sep 01, 2020 at 05:40:36PM -0400, Josef Bacik wrote:
> Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Added to misc-next, thanks.
On 3/9/20 1:45 am, David Sterba wrote: > On Wed, Sep 02, 2020 at 02:21:31PM +0800, Anand Jain wrote: >>> @@ -2609,6 +2606,10 @@ int btrfs_init_new_device(struct btrfs_fs_info *fs_info, const char *device_path >>> btrfs_clear_space_info_full(fs_info); >>> >>> mutex_unlock(&fs_info->chunk_mutex); >>> + >>> + /* add sysfs device entry */ >>> + btrfs_sysfs_add_devices_dir(fs_devices, device); >>> + >>> mutex_unlock(&fs_devices->device_list_mutex); >>> >>> if (seeding_dev) { >>> >> >> Strange we should get this splat when btrfs_sysfs_add_devices_dir() >> already has implicit GFP_NOFS allocation scope right? What did I >> miss? > > The problem is the sysfs' kernfs_mutex, all sysfs allocations are > GFP_KERNEL thus it can grab fs_reclaim at some point. > Oh. Thanks. Anand
On 3/9/20 1:45 am, David Sterba wrote: > On Wed, Sep 02, 2020 at 02:21:31PM +0800, Anand Jain wrote: >>> @@ -2609,6 +2606,10 @@ int btrfs_init_new_device(struct btrfs_fs_info *fs_info, const char *device_path >>> btrfs_clear_space_info_full(fs_info); >>> >>> mutex_unlock(&fs_info->chunk_mutex); >>> + >>> + /* add sysfs device entry */ >>> + btrfs_sysfs_add_devices_dir(fs_devices, device); >>> + >>> mutex_unlock(&fs_devices->device_list_mutex); >>> >>> if (seeding_dev) { >>> >> >> Strange we should get this splat when btrfs_sysfs_add_devices_dir() >> already has implicit GFP_NOFS allocation scope right? What did I >> miss? > > The problem is the sysfs' kernfs_mutex, all sysfs allocations are > GFP_KERNEL thus it can grab fs_reclaim at some point. > Oh. Thanks. Reviewed-by: Anand Jain <anand.jain@oracle.com> Anand
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c index d6bbbe1986bb..77b7da42c651 100644 --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -2599,9 +2599,6 @@ int btrfs_init_new_device(struct btrfs_fs_info *fs_info, const char *device_path btrfs_set_super_num_devices(fs_info->super_copy, orig_super_num_devices + 1); - /* add sysfs device entry */ - btrfs_sysfs_add_devices_dir(fs_devices, device); - /* * we've got more storage, clear any full flags on the space * infos @@ -2609,6 +2606,10 @@ int btrfs_init_new_device(struct btrfs_fs_info *fs_info, const char *device_path btrfs_clear_space_info_full(fs_info); mutex_unlock(&fs_info->chunk_mutex); + + /* add sysfs device entry */ + btrfs_sysfs_add_devices_dir(fs_devices, device); + mutex_unlock(&fs_devices->device_list_mutex); if (seeding_dev) {
While running btrfs/187 I hit the following lockdep splat ====================================================== WARNING: possible circular locking dependency detected 5.9.0-rc3+ #4 Not tainted ------------------------------------------------------ kswapd0/100 is trying to acquire lock: ffff96ecc22ef4a0 (&delayed_node->mutex){+.+.}-{3:3}, at: __btrfs_release_delayed_node.part.0+0x3f/0x330 but task is already holding lock: ffffffff8dd74700 (fs_reclaim){+.+.}-{0:0}, at: __fs_reclaim_acquire+0x5/0x30 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #3 (fs_reclaim){+.+.}-{0:0}: fs_reclaim_acquire+0x65/0x80 slab_pre_alloc_hook.constprop.0+0x20/0x200 kmem_cache_alloc+0x37/0x270 alloc_inode+0x82/0xb0 iget_locked+0x10d/0x2c0 kernfs_get_inode+0x1b/0x130 kernfs_get_tree+0x136/0x240 sysfs_get_tree+0x16/0x40 vfs_get_tree+0x28/0xc0 path_mount+0x434/0xc00 __x64_sys_mount+0xe3/0x120 do_syscall_64+0x33/0x40 entry_SYSCALL_64_after_hwframe+0x44/0xa9 -> #2 (kernfs_mutex){+.+.}-{3:3}: __mutex_lock+0x7e/0x7e0 kernfs_add_one+0x23/0x150 kernfs_create_link+0x63/0xa0 sysfs_do_create_link_sd+0x5e/0xd0 btrfs_sysfs_add_devices_dir+0x81/0x130 btrfs_init_new_device+0x67f/0x1250 btrfs_ioctl+0x1ef/0x2e20 __x64_sys_ioctl+0x83/0xb0 do_syscall_64+0x33/0x40 entry_SYSCALL_64_after_hwframe+0x44/0xa9 -> #1 (&fs_info->chunk_mutex){+.+.}-{3:3}: __mutex_lock+0x7e/0x7e0 btrfs_chunk_alloc+0x125/0x3a0 find_free_extent+0xdf6/0x1210 btrfs_reserve_extent+0xb3/0x1b0 btrfs_alloc_tree_block+0xb0/0x310 alloc_tree_block_no_bg_flush+0x4a/0x60 __btrfs_cow_block+0x11a/0x530 btrfs_cow_block+0x104/0x220 btrfs_search_slot+0x52e/0x9d0 btrfs_insert_empty_items+0x64/0xb0 btrfs_insert_delayed_items+0x90/0x4f0 btrfs_commit_inode_delayed_items+0x93/0x140 btrfs_log_inode+0x5de/0x2020 btrfs_log_inode_parent+0x429/0xc90 btrfs_log_new_name+0x95/0x9b btrfs_rename2+0xbb9/0x1800 vfs_rename+0x64f/0x9f0 do_renameat2+0x320/0x4e0 __x64_sys_rename+0x1f/0x30 do_syscall_64+0x33/0x40 entry_SYSCALL_64_after_hwframe+0x44/0xa9 -> #0 (&delayed_node->mutex){+.+.}-{3:3}: __lock_acquire+0x119c/0x1fc0 lock_acquire+0xa7/0x3d0 __mutex_lock+0x7e/0x7e0 __btrfs_release_delayed_node.part.0+0x3f/0x330 btrfs_evict_inode+0x24c/0x500 evict+0xcf/0x1f0 dispose_list+0x48/0x70 prune_icache_sb+0x44/0x50 super_cache_scan+0x161/0x1e0 do_shrink_slab+0x178/0x3c0 shrink_slab+0x17c/0x290 shrink_node+0x2b2/0x6d0 balance_pgdat+0x30a/0x670 kswapd+0x213/0x4c0 kthread+0x138/0x160 ret_from_fork+0x1f/0x30 other info that might help us debug this: Chain exists of: &delayed_node->mutex --> kernfs_mutex --> fs_reclaim Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(fs_reclaim); lock(kernfs_mutex); lock(fs_reclaim); lock(&delayed_node->mutex); *** DEADLOCK *** 3 locks held by kswapd0/100: #0: ffffffff8dd74700 (fs_reclaim){+.+.}-{0:0}, at: __fs_reclaim_acquire+0x5/0x30 #1: ffffffff8dd65c50 (shrinker_rwsem){++++}-{3:3}, at: shrink_slab+0x115/0x290 #2: ffff96ed2ade30e0 (&type->s_umount_key#36){++++}-{3:3}, at: super_cache_scan+0x38/0x1e0 stack backtrace: CPU: 0 PID: 100 Comm: kswapd0 Not tainted 5.9.0-rc3+ #4 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.13.0-2.fc32 04/01/2014 Call Trace: dump_stack+0x8b/0xb8 check_noncircular+0x12d/0x150 __lock_acquire+0x119c/0x1fc0 lock_acquire+0xa7/0x3d0 ? __btrfs_release_delayed_node.part.0+0x3f/0x330 __mutex_lock+0x7e/0x7e0 ? __btrfs_release_delayed_node.part.0+0x3f/0x330 ? __btrfs_release_delayed_node.part.0+0x3f/0x330 ? lock_acquire+0xa7/0x3d0 ? find_held_lock+0x2b/0x80 __btrfs_release_delayed_node.part.0+0x3f/0x330 btrfs_evict_inode+0x24c/0x500 evict+0xcf/0x1f0 dispose_list+0x48/0x70 prune_icache_sb+0x44/0x50 super_cache_scan+0x161/0x1e0 do_shrink_slab+0x178/0x3c0 shrink_slab+0x17c/0x290 shrink_node+0x2b2/0x6d0 balance_pgdat+0x30a/0x670 kswapd+0x213/0x4c0 ? _raw_spin_unlock_irqrestore+0x41/0x50 ? add_wait_queue_exclusive+0x70/0x70 ? balance_pgdat+0x670/0x670 kthread+0x138/0x160 ? kthread_create_worker_on_cpu+0x40/0x40 ret_from_fork+0x1f/0x30 This happens because we are holding the chunk_mutex at the time of adding in a new device. However we only need to hold the device_list_mutex, as we're going to iterate over the fs_devices devices. Move the sysfs init stuff outside of the chunk_mutex to get rid of this lockdep splat. Signed-off-by: Josef Bacik <josef@toxicpanda.com> --- fs/btrfs/volumes.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-)