| Message ID | a13181cccb5b199b9127016bfcc29a2476aba891.1720106304.git.fdmanana@suse.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | btrfs: use delayed iput during extent map shrinking | expand |
On Thu, Jul 04, 2024 at 04:18:42PM +0100, fdmanana@kernel.org wrote: > From: Filipe Manana <fdmanana@suse.com> > > When putting an inode during extent map shrinking we're doing a standard > iput() but that may take a long time in case the inode is dirty and we are > doing the final iput that triggers eviction - the VFS will have to wait > for writeback before calling the btrfs evict callback (see > fs/inode.c:evict()). > > This slows down the task running the shrinker which may have been > triggered while updating some tree for example, meaning locks are held > as well as an open transaction handle. > > Also if the iput() ends up triggering eviction and the inode has no links > anymore, then we trigger item truncation which requires flushing delayed > items, space reservation to start a transaction and that may trigger the > space reclaim task and wait for it, resulting in deadlocks in case the > reclaim task needs for example to commit a transaction and the shrinker > is being triggered from a path holding a transaction handle. > > Syzbot reported such a case with the following stack traces: > > ====================================================== > WARNING: possible circular locking dependency detected > 6.10.0-rc2-syzkaller-00010-g2ab795141095 #0 Not tainted > ------------------------------------------------------ > kswapd0/111 is trying to acquire lock: > ffff88801eae4610 (sb_internal#3){.+.+}-{0:0}, at: btrfs_commit_inode_delayed_inode+0x110/0x330 fs/btrfs/delayed-inode.c:1275 > > but task is already holding lock: > ffffffff8dd3a9a0 (fs_reclaim){+.+.}-{0:0}, at: balance_pgdat+0xa88/0x1970 mm/vmscan.c:6924 > > which lock already depends on the new lock. > > the existing dependency chain (in reverse order) is: > > -> #3 (fs_reclaim){+.+.}-{0:0}: > __fs_reclaim_acquire mm/page_alloc.c:3783 [inline] > fs_reclaim_acquire+0x102/0x160 mm/page_alloc.c:3797 > might_alloc include/linux/sched/mm.h:334 [inline] > slab_pre_alloc_hook mm/slub.c:3890 [inline] > slab_alloc_node mm/slub.c:3980 [inline] > kmem_cache_alloc_lru_noprof+0x58/0x2f0 mm/slub.c:4019 > btrfs_alloc_inode+0x118/0xb20 fs/btrfs/inode.c:8411 > alloc_inode+0x5d/0x230 fs/inode.c:261 > iget5_locked fs/inode.c:1235 [inline] > iget5_locked+0x1c9/0x2c0 fs/inode.c:1228 > btrfs_iget_locked fs/btrfs/inode.c:5590 [inline] > btrfs_iget_path fs/btrfs/inode.c:5607 [inline] > btrfs_iget+0xfb/0x230 fs/btrfs/inode.c:5636 > create_reloc_inode+0x403/0x820 fs/btrfs/relocation.c:3911 > btrfs_relocate_block_group+0x471/0xe60 fs/btrfs/relocation.c:4114 > btrfs_relocate_chunk+0x143/0x450 fs/btrfs/volumes.c:3373 > __btrfs_balance fs/btrfs/volumes.c:4157 [inline] > btrfs_balance+0x211a/0x3f00 fs/btrfs/volumes.c:4534 > btrfs_ioctl_balance fs/btrfs/ioctl.c:3675 [inline] > btrfs_ioctl+0x12ed/0x8290 fs/btrfs/ioctl.c:4742 > __do_compat_sys_ioctl+0x2c3/0x330 fs/ioctl.c:1007 > do_syscall_32_irqs_on arch/x86/entry/common.c:165 [inline] > __do_fast_syscall_32+0x73/0x120 arch/x86/entry/common.c:386 > do_fast_syscall_32+0x32/0x80 arch/x86/entry/common.c:411 > entry_SYSENTER_compat_after_hwframe+0x84/0x8e > > -> #2 (btrfs_trans_num_extwriters){++++}-{0:0}: > join_transaction+0x164/0xf40 fs/btrfs/transaction.c:315 > start_transaction+0x427/0x1a70 fs/btrfs/transaction.c:700 > btrfs_rebuild_free_space_tree+0xaa/0x480 fs/btrfs/free-space-tree.c:1323 > btrfs_start_pre_rw_mount+0x218/0xf60 fs/btrfs/disk-io.c:2999 > open_ctree+0x41ab/0x52e0 fs/btrfs/disk-io.c:3554 > btrfs_fill_super fs/btrfs/super.c:946 [inline] > btrfs_get_tree_super fs/btrfs/super.c:1863 [inline] > btrfs_get_tree+0x11e9/0x1b90 fs/btrfs/super.c:2089 > vfs_get_tree+0x8f/0x380 fs/super.c:1780 > fc_mount+0x16/0xc0 fs/namespace.c:1125 > btrfs_get_tree_subvol fs/btrfs/super.c:2052 [inline] > btrfs_get_tree+0xa53/0x1b90 fs/btrfs/super.c:2090 > vfs_get_tree+0x8f/0x380 fs/super.c:1780 > do_new_mount fs/namespace.c:3352 [inline] > path_mount+0x6e1/0x1f10 fs/namespace.c:3679 > do_mount fs/namespace.c:3692 [inline] > __do_sys_mount fs/namespace.c:3898 [inline] > __se_sys_mount fs/namespace.c:3875 [inline] > __ia32_sys_mount+0x295/0x320 fs/namespace.c:3875 > do_syscall_32_irqs_on arch/x86/entry/common.c:165 [inline] > __do_fast_syscall_32+0x73/0x120 arch/x86/entry/common.c:386 > do_fast_syscall_32+0x32/0x80 arch/x86/entry/common.c:411 > entry_SYSENTER_compat_after_hwframe+0x84/0x8e > > -> #1 (btrfs_trans_num_writers){++++}-{0:0}: > join_transaction+0x148/0xf40 fs/btrfs/transaction.c:314 > start_transaction+0x427/0x1a70 fs/btrfs/transaction.c:700 > btrfs_rebuild_free_space_tree+0xaa/0x480 fs/btrfs/free-space-tree.c:1323 > btrfs_start_pre_rw_mount+0x218/0xf60 fs/btrfs/disk-io.c:2999 > open_ctree+0x41ab/0x52e0 fs/btrfs/disk-io.c:3554 > btrfs_fill_super fs/btrfs/super.c:946 [inline] > btrfs_get_tree_super fs/btrfs/super.c:1863 [inline] > btrfs_get_tree+0x11e9/0x1b90 fs/btrfs/super.c:2089 > vfs_get_tree+0x8f/0x380 fs/super.c:1780 > fc_mount+0x16/0xc0 fs/namespace.c:1125 > btrfs_get_tree_subvol fs/btrfs/super.c:2052 [inline] > btrfs_get_tree+0xa53/0x1b90 fs/btrfs/super.c:2090 > vfs_get_tree+0x8f/0x380 fs/super.c:1780 > do_new_mount fs/namespace.c:3352 [inline] > path_mount+0x6e1/0x1f10 fs/namespace.c:3679 > do_mount fs/namespace.c:3692 [inline] > __do_sys_mount fs/namespace.c:3898 [inline] > __se_sys_mount fs/namespace.c:3875 [inline] > __ia32_sys_mount+0x295/0x320 fs/namespace.c:3875 > do_syscall_32_irqs_on arch/x86/entry/common.c:165 [inline] > __do_fast_syscall_32+0x73/0x120 arch/x86/entry/common.c:386 > do_fast_syscall_32+0x32/0x80 arch/x86/entry/common.c:411 > entry_SYSENTER_compat_after_hwframe+0x84/0x8e > > -> #0 (sb_internal#3){.+.+}-{0:0}: > check_prev_add kernel/locking/lockdep.c:3134 [inline] > check_prevs_add kernel/locking/lockdep.c:3253 [inline] > validate_chain kernel/locking/lockdep.c:3869 [inline] > __lock_acquire+0x2478/0x3b30 kernel/locking/lockdep.c:5137 > lock_acquire kernel/locking/lockdep.c:5754 [inline] > lock_acquire+0x1b1/0x560 kernel/locking/lockdep.c:5719 > percpu_down_read include/linux/percpu-rwsem.h:51 [inline] > __sb_start_write include/linux/fs.h:1655 [inline] > sb_start_intwrite include/linux/fs.h:1838 [inline] > start_transaction+0xbc1/0x1a70 fs/btrfs/transaction.c:694 > btrfs_commit_inode_delayed_inode+0x110/0x330 fs/btrfs/delayed-inode.c:1275 > btrfs_evict_inode+0x960/0xe80 fs/btrfs/inode.c:5291 > evict+0x2ed/0x6c0 fs/inode.c:667 > iput_final fs/inode.c:1741 [inline] > iput.part.0+0x5a8/0x7f0 fs/inode.c:1767 > iput+0x5c/0x80 fs/inode.c:1757 > btrfs_scan_root fs/btrfs/extent_map.c:1118 [inline] > btrfs_free_extent_maps+0xbd3/0x1320 fs/btrfs/extent_map.c:1189 > super_cache_scan+0x409/0x550 fs/super.c:227 > do_shrink_slab+0x44f/0x11c0 mm/shrinker.c:435 > shrink_slab+0x18a/0x1310 mm/shrinker.c:662 > shrink_one+0x493/0x7c0 mm/vmscan.c:4790 > shrink_many mm/vmscan.c:4851 [inline] > lru_gen_shrink_node+0x89f/0x1750 mm/vmscan.c:4951 > shrink_node mm/vmscan.c:5910 [inline] > kswapd_shrink_node mm/vmscan.c:6720 [inline] > balance_pgdat+0x1105/0x1970 mm/vmscan.c:6911 > kswapd+0x5ea/0xbf0 mm/vmscan.c:7180 > kthread+0x2c1/0x3a0 kernel/kthread.c:389 > ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147 > ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244 > > other info that might help us debug this: > > Chain exists of: > sb_internal#3 --> btrfs_trans_num_extwriters --> fs_reclaim > > Possible unsafe locking scenario: > > CPU0 CPU1 > ---- ---- > lock(fs_reclaim); > lock(btrfs_trans_num_extwriters); > lock(fs_reclaim); > rlock(sb_internal#3); > > *** DEADLOCK *** > > 2 locks held by kswapd0/111: > #0: ffffffff8dd3a9a0 (fs_reclaim){+.+.}-{0:0}, at: balance_pgdat+0xa88/0x1970 mm/vmscan.c:6924 > #1: ffff88801eae40e0 (&type->s_umount_key#62){++++}-{3:3}, at: super_trylock_shared fs/super.c:562 [inline] > #1: ffff88801eae40e0 (&type->s_umount_key#62){++++}-{3:3}, at: super_cache_scan+0x96/0x550 fs/super.c:196 > > stack backtrace: > CPU: 0 PID: 111 Comm: kswapd0 Not tainted 6.10.0-rc2-syzkaller-00010-g2ab795141095 #0 > Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014 > Call Trace: > <TASK> > __dump_stack lib/dump_stack.c:88 [inline] > dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:114 > check_noncircular+0x31a/0x400 kernel/locking/lockdep.c:2187 > check_prev_add kernel/locking/lockdep.c:3134 [inline] > check_prevs_add kernel/locking/lockdep.c:3253 [inline] > validate_chain kernel/locking/lockdep.c:3869 [inline] > __lock_acquire+0x2478/0x3b30 kernel/locking/lockdep.c:5137 > lock_acquire kernel/locking/lockdep.c:5754 [inline] > lock_acquire+0x1b1/0x560 kernel/locking/lockdep.c:5719 > percpu_down_read include/linux/percpu-rwsem.h:51 [inline] > __sb_start_write include/linux/fs.h:1655 [inline] > sb_start_intwrite include/linux/fs.h:1838 [inline] > start_transaction+0xbc1/0x1a70 fs/btrfs/transaction.c:694 > btrfs_commit_inode_delayed_inode+0x110/0x330 fs/btrfs/delayed-inode.c:1275 > btrfs_evict_inode+0x960/0xe80 fs/btrfs/inode.c:5291 > evict+0x2ed/0x6c0 fs/inode.c:667 > iput_final fs/inode.c:1741 [inline] > iput.part.0+0x5a8/0x7f0 fs/inode.c:1767 > iput+0x5c/0x80 fs/inode.c:1757 > btrfs_scan_root fs/btrfs/extent_map.c:1118 [inline] > btrfs_free_extent_maps+0xbd3/0x1320 fs/btrfs/extent_map.c:1189 > super_cache_scan+0x409/0x550 fs/super.c:227 > do_shrink_slab+0x44f/0x11c0 mm/shrinker.c:435 > shrink_slab+0x18a/0x1310 mm/shrinker.c:662 > shrink_one+0x493/0x7c0 mm/vmscan.c:4790 > shrink_many mm/vmscan.c:4851 [inline] > lru_gen_shrink_node+0x89f/0x1750 mm/vmscan.c:4951 > shrink_node mm/vmscan.c:5910 [inline] > kswapd_shrink_node mm/vmscan.c:6720 [inline] > balance_pgdat+0x1105/0x1970 mm/vmscan.c:6911 > kswapd+0x5ea/0xbf0 mm/vmscan.c:7180 > kthread+0x2c1/0x3a0 kernel/kthread.c:389 > ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147 > ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244 > </TASK> > > So fix this by using btrfs_add_delayed_iput() so that the final iput is > delegated to the cleaner kthread. > > Link: https://lore.kernel.org/linux-btrfs/000000000000892280061a344581@google.com/ > Reported-by: syzbot+3dad89b3993a4b275e72@syzkaller.appspotmail.com > Fixes: 956a17d9d050 ("btrfs: add a shrinker for extent maps") > Signed-off-by: Filipe Manana <fdmanana@suse.com> Reviewed-by: David Sterba <dsterba@suse.com>
diff --git a/fs/btrfs/extent_map.c b/fs/btrfs/extent_map.c index 54e3a52f2280..7c03016441ab 100644 --- a/fs/btrfs/extent_map.c +++ b/fs/btrfs/extent_map.c @@ -1211,7 +1211,7 @@ static long btrfs_scan_root(struct btrfs_root *root, long *scanned, long nr_to_s min_ino = btrfs_ino(inode) + 1; fs_info->extent_map_shrinker_last_ino = btrfs_ino(inode); - iput(&inode->vfs_inode); + btrfs_add_delayed_iput(inode); if (*scanned >= nr_to_scan) break;