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If anyone has any objections, please let me know. ------------------ From: Sergey Senozhatsky [ Upstream commit 19e16597f9baf1b5719a3a6c710486446f6808fd ] We observe the following ABBA deadlock (casefolding enabled): INFO: task jbd2/dm-13-8:447 blocked for more than 720 seconds. task:jbd2/dm-13-8 state:D stack:0 pid:447 tgid:447 ppid:2 Call Trace: __schedule+0xc2c/0xe60 schedule+0x40/0xe0 jbd2_journal_wait_updates+0x8f/0xf0 jbd2_journal_commit_transaction+0x321/0x1850 kjournald2+0xa9/0x230 kthread+0x226/0x2a0 ret_from_fork+0x101/0x1e0 ret_from_fork_asm+0x1a/0x30 INFO: task Thread-10:4161 blocked for more than 720 seconds. task:Thread-10 state:D stack:0 pid:4161 tgid:3848 ppid:540 Call Trace: __schedule+0xc2c/0xe60 schedule+0x40/0xe0 wait_transaction_locked+0x8c/0xd0 start_this_handle+0x252/0x870 jbd2__journal_start+0x120/0x280 __ext4_journal_start_sb+0x11a/0x250 ext4_evict_inode+0x208/0x760 iput+0x222/0x5c0 dput+0x293/0x690 ____fput+0x145/0x2b0 task_work_run+0x7a/0xb0 exit_to_user_mode_loop+0xc0/0xd0 do_syscall_64+0x14b/0xf10 entry_SYSCALL_64_after_hwframe+0x76/0x7e NMI backtrace for cpu 0 CPU: 0 UID: 1010216 PID: 4160 Comm: Thread-7 RIP: 0010:d_walk+0x0/0x290 [..] Call Trace: shrink_dcache_parent+0xb2/0x100 d_invalidate+0x50/0x110 ext4_rmdir+0x3a2/0x3d0 vfs_rmdir+0x9d/0x1d0 do_rmdir+0xf0/0x330 __x64_sys_unlinkat+0x34/0x50 do_syscall_64+0x61/0xf10 The problem is that ext4_rmdir() calls d_invalidate() before stopping the jbd2 transaction handle. Because d_invalidate() traverses child dentries it can encounter dying or in-use dentries. If a concurrent thread executing __dentry_kill() on a child dentry invokes ext4_evict_inode(), it requests a new transaction handle via ext4_journal_start(), which waits for all running handles to close. However, the thread executing ext4_rmdir() still holds its active transaction handle while looping in shrink_dcache_parent() waiting for the dying child dentry to complete eviction. Stop transaction handle in ext4_rmdir() before calling d_invalidate(). Cc: stable@kernel.org Fixes: b886ee3e778e ("ext4: Support case-insensitive file name lookups") Co-developed-by: Sarthak Kukreti Signed-off-by: Sarthak Kukreti Signed-off-by: Sergey Senozhatsky Reviewed-by: Jan Kara Reviewed-by: Baokun Li Reviewed-by: Zhang Yi Link: https://patch.msgid.link/20260827125158.4030598-1-senozhatsky@chromium.org Signed-off-by: Theodore Ts'o Signed-off-by: Sasha Levin --- fs/ext4/namei.c | 11 ++++++----- 1 file changed, 6 insertions(+), 5 deletions(-) diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c index 2c661155158f8..49bd70aab2255 100644 --- a/fs/ext4/namei.c +++ b/fs/ext4/namei.c @@ -3204,19 +3204,20 @@ static int ext4_rmdir(struct inode *dir, struct dentry *dentry) ext4_fc_track_unlink(handle, dentry); retval = ext4_mark_inode_dirty(handle, dir); +end_rmdir: + brelse(bh); + if (handle) + ext4_journal_stop(handle); + /* VFS negative dentries are incompatible with Encoding and * Case-insensitiveness. Eventually we'll want avoid * invalidating the dentries here, alongside with returning the * negative dentries at ext4_lookup(), when it is better * supported by the VFS for the CI case. */ - if (IS_ENABLED(CONFIG_UNICODE) && IS_CASEFOLDED(dir)) + if (!retval && IS_ENABLED(CONFIG_UNICODE) && IS_CASEFOLDED(dir)) d_invalidate(dentry); -end_rmdir: - brelse(bh); - if (handle) - ext4_journal_stop(handle); return retval; } -- 2.53.0