syzbot

======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
kworker/u4:2/154 is trying to acquire lock:
ffff888058c828a8 (&ei->xattr_sem){++++}-{3:3}, at: ext4_write_lock_xattr fs/ext4/xattr.h:155 [inline]
ffff888058c828a8 (&ei->xattr_sem){++++}-{3:3}, at: ext4_destroy_inline_data+0x24/0xe0 fs/ext4/inline.c:1890

but task is already holding lock:
ffff88807d504bd8 (&sbi->s_writepages_rwsem){++++}-{0:0}, at: ext4_writepages+0x1c0/0x2d20 fs/ext4/inode.c:2689

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (&sbi->s_writepages_rwsem){++++}-{0:0}:
       percpu_down_read+0x46/0x1b0 include/linux/percpu-rwsem.h:51
       ext4_writepages+0x1c0/0x2d20 fs/ext4/inode.c:2689
       do_writepages+0x48d/0x6d0 mm/page-writeback.c:2386
       __writeback_single_inode+0x153/0xda0 fs/fs-writeback.c:1657
       writeback_single_inode+0x221/0x8b0 fs/fs-writeback.c:1770
       write_inode_now+0x217/0x280 fs/fs-writeback.c:2811
       iput_final fs/inode.c:1756 [inline]
       iput+0x5ab/0x8a0 fs/inode.c:1795
       ext4_xattr_set_entry+0x10ff/0x3d30 fs/ext4/xattr.c:1837
       ext4_xattr_block_set+0x4f7/0x2d30 fs/ext4/xattr.c:1936
       ext4_xattr_move_to_block fs/ext4/xattr.c:2633 [inline]
       ext4_xattr_make_inode_space fs/ext4/xattr.c:2708 [inline]
       ext4_expand_extra_isize_ea+0xf4b/0x19a0 fs/ext4/xattr.c:2800
       __ext4_expand_extra_isize+0x301/0x3e0 fs/ext4/inode.c:5901
       ext4_try_to_expand_extra_isize fs/ext4/inode.c:5944 [inline]
       __ext4_mark_inode_dirty+0x469/0x700 fs/ext4/inode.c:6022
       ext4_evict_inode+0xa81/0x1080 fs/ext4/inode.c:282
       evict+0x485/0x870 fs/inode.c:647
       ext4_orphan_cleanup+0xaa9/0x12e0 fs/ext4/orphan.c:470
       ext4_fill_super+0x92f0/0x9a60 fs/ext4/super.c:4975
       mount_bdev+0x287/0x3c0 fs/super.c:1400
       legacy_get_tree+0xe6/0x180 fs/fs_context.c:611
       vfs_get_tree+0x88/0x270 fs/super.c:1530
       do_new_mount+0x24a/0xa40 fs/namespace.c:3034
       do_mount fs/namespace.c:3377 [inline]
       __do_sys_mount fs/namespace.c:3585 [inline]
       __se_sys_mount+0x2d6/0x3c0 fs/namespace.c:3562
       do_syscall_x64 arch/x86/entry/common.c:50 [inline]
       do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
       entry_SYSCALL_64_after_hwframe+0x66/0xd0

-> #0 (&ei->xattr_sem){++++}-{3:3}:
       check_prev_add kernel/locking/lockdep.c:3053 [inline]
       check_prevs_add kernel/locking/lockdep.c:3172 [inline]
       validate_chain kernel/locking/lockdep.c:3788 [inline]
       __lock_acquire+0x2c33/0x7c60 kernel/locking/lockdep.c:5012
       lock_acquire+0x197/0x3f0 kernel/locking/lockdep.c:5623
       down_write+0x38/0x60 kernel/locking/rwsem.c:1551
       ext4_write_lock_xattr fs/ext4/xattr.h:155 [inline]
       ext4_destroy_inline_data+0x24/0xe0 fs/ext4/inline.c:1890
       ext4_writepages+0x5df/0x2d20 fs/ext4/inode.c:2735
       do_writepages+0x48d/0x6d0 mm/page-writeback.c:2386
       __writeback_single_inode+0x153/0xda0 fs/fs-writeback.c:1657
       writeback_sb_inodes+0x9fe/0x1610 fs/fs-writeback.c:1940
       wb_writeback+0x443/0xb90 fs/fs-writeback.c:2114
       wb_do_writeback fs/fs-writeback.c:2257 [inline]
       wb_workfn+0x423/0xe60 fs/fs-writeback.c:2298
       process_one_work+0x863/0x1000 kernel/workqueue.c:2310
       worker_thread+0xaa8/0x12a0 kernel/workqueue.c:2457
       kthread+0x436/0x520 kernel/kthread.c:334
       ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287

other info that might help us debug this:

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&sbi->s_writepages_rwsem);
                               lock(&ei->xattr_sem);
                               lock(&sbi->s_writepages_rwsem);
  lock(&ei->xattr_sem);

 *** DEADLOCK ***

3 locks held by kworker/u4:2/154:
 #0: ffff8880191f0938 ((wq_completion)writeback
){+.+.}-{0:0}, at: process_one_work+0x760/0x1000 kernel/workqueue.c:-1
 #1: ffffc90001ff7d00 ((work_completion)(&(&wb->dwork)->work)){+.+.}-{0:0}, at: process_one_work+0x7a3/0x1000 kernel/workqueue.c:2285
 #2: ffff88807d504bd8 (&sbi->s_writepages_rwsem){++++}-{0:0}, at: ext4_writepages+0x1c0/0x2d20 fs/ext4/inode.c:2689

stack backtrace:
CPU: 1 PID: 154 Comm: kworker/u4:2 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
Workqueue: writeback wb_workfn (flush-7:0)
Call Trace:
 <TASK>
 dump_stack_lvl+0x168/0x230 lib/dump_stack.c:106
 check_noncircular+0x274/0x310 kernel/locking/lockdep.c:2133
 check_prev_add kernel/locking/lockdep.c:3053 [inline]
 check_prevs_add kernel/locking/lockdep.c:3172 [inline]
 validate_chain kernel/locking/lockdep.c:3788 [inline]
 __lock_acquire+0x2c33/0x7c60 kernel/locking/lockdep.c:5012
 lock_acquire+0x197/0x3f0 kernel/locking/lockdep.c:5623
 down_write+0x38/0x60 kernel/locking/rwsem.c:1551
 ext4_write_lock_xattr fs/ext4/xattr.h:155 [inline]
 ext4_destroy_inline_data+0x24/0xe0 fs/ext4/inline.c:1890
 ext4_writepages+0x5df/0x2d20 fs/ext4/inode.c:2735
 do_writepages+0x48d/0x6d0 mm/page-writeback.c:2386
 __writeback_single_inode+0x153/0xda0 fs/fs-writeback.c:1657
 writeback_sb_inodes+0x9fe/0x1610 fs/fs-writeback.c:1940
 wb_writeback+0x443/0xb90 fs/fs-writeback.c:2114
 wb_do_writeback fs/fs-writeback.c:2257 [inline]
 wb_workfn+0x423/0xe60 fs/fs-writeback.c:2298
 process_one_work+0x863/0x1000 kernel/workqueue.c:2310
 worker_thread+0xaa8/0x12a0 kernel/workqueue.c:2457
 kthread+0x436/0x520 kernel/kthread.c:334
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
 </TASK>
EXT4-fs error (device loop0): ext4_mb_generate_buddy:1147: group 0, block bitmap and bg descriptor inconsistent: 25 vs 4278190105 free clusters
EXT4-fs (loop0): Delayed block allocation failed for inode 15 at logical offset 0 with max blocks 1 with error 28
EXT4-fs (loop0): This should not happen!! Data will be lost

EXT4-fs (loop0): Total free blocks count 0
EXT4-fs (loop0): Free/Dirty block details
EXT4-fs (loop0): free_blocks=68451041280
EXT4-fs (loop0): dirty_blocks=0
EXT4-fs (loop0): Block reservation details
EXT4-fs (loop0): i_reserved_data_blocks=0