syzbot

======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
kworker/u4:5/985 is trying to acquire lock:
ffff888077d5d0c8 (&ei->xattr_sem){++++}-{3:3}, at: ext4_write_lock_xattr fs/ext4/xattr.h:158 [inline]
ffff888077d5d0c8 (&ei->xattr_sem){++++}-{3:3}, at: ext4_destroy_inline_data+0x28/0xe0 fs/ext4/inline.c:1894

but task is already holding lock:
ffff88802cb30bd8 (&sbi->s_writepages_rwsem){++++}-{0:0}, at: ext4_writepages_down_read fs/ext4/ext4.h:1767 [inline]
ffff88802cb30bd8 (&sbi->s_writepages_rwsem){++++}-{0:0}, at: ext4_writepages+0x1a4/0x350 fs/ext4/inode.c:2806

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+0x44/0x1a0 include/linux/percpu-rwsem.h:51
       ext4_writepages_down_read fs/ext4/ext4.h:1767 [inline]
       ext4_writepages+0x1a4/0x350 fs/ext4/inode.c:2806
       do_writepages+0x3b3/0x630 mm/page-writeback.c:2575
       __writeback_single_inode+0x153/0xec0 fs/fs-writeback.c:1635
       writeback_single_inode+0x21f/0x760 fs/fs-writeback.c:1756
       write_inode_now+0x183/0x210 fs/fs-writeback.c:2808
       iput_final fs/inode.c:1807 [inline]
       iput+0x5ae/0x920 fs/inode.c:1846
       ext4_xattr_block_set+0x273f/0x32b0 fs/ext4/xattr.c:2199
       ext4_xattr_move_to_block fs/ext4/xattr.c:2664 [inline]
       ext4_xattr_make_inode_space fs/ext4/xattr.c:2739 [inline]
       ext4_expand_extra_isize_ea+0x12c5/0x1e80 fs/ext4/xattr.c:2827
       __ext4_expand_extra_isize+0x306/0x400 fs/ext4/inode.c:5971
       ext4_try_to_expand_extra_isize fs/ext4/inode.c:6014 [inline]
       __ext4_mark_inode_dirty+0x45d/0x6e0 fs/ext4/inode.c:6092
       ext4_evict_inode+0x7f3/0xea0 fs/ext4/inode.c:252
       evict+0x4ca/0x8d0 fs/inode.c:705
       ext4_orphan_cleanup+0xbec/0x1420 fs/ext4/orphan.c:472
       __ext4_fill_super fs/ext4/super.c:5617 [inline]
       ext4_fill_super+0x5ed0/0x6790 fs/ext4/super.c:5740
       get_tree_bdev+0x3f3/0x520 fs/super.c:1591
       vfs_get_tree+0x8c/0x280 fs/super.c:1764
       do_new_mount+0x24b/0xa40 fs/namespace.c:3386
       do_mount fs/namespace.c:3726 [inline]
       __do_sys_mount fs/namespace.c:3935 [inline]
       __se_sys_mount+0x2e7/0x3d0 fs/namespace.c:3912
       do_syscall_x64 arch/x86/entry/common.c:46 [inline]
       do_syscall_64+0x55/0xa0 arch/x86/entry/common.c:76
       entry_SYSCALL_64_after_hwframe+0x68/0xd2

-> #0 (&ei->xattr_sem){++++}-{3:3}:
       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+0x2df1/0x7d40 kernel/locking/lockdep.c:5137
       lock_acquire+0x19e/0x420 kernel/locking/lockdep.c:5754
       down_write+0x97/0x200 kernel/locking/rwsem.c:1573
       ext4_write_lock_xattr fs/ext4/xattr.h:158 [inline]
       ext4_destroy_inline_data+0x28/0xe0 fs/ext4/inline.c:1894
       ext4_do_writepages+0x4f0/0x3990 fs/ext4/inode.c:2604
       ext4_writepages+0x1dd/0x350 fs/ext4/inode.c:2807
       do_writepages+0x3b3/0x630 mm/page-writeback.c:2575
       __writeback_single_inode+0x153/0xec0 fs/fs-writeback.c:1635
       writeback_sb_inodes+0x7cd/0xf50 fs/fs-writeback.c:1926
       wb_writeback+0x46a/0xbf0 fs/fs-writeback.c:2105
       wb_do_writeback fs/fs-writeback.c:2252 [inline]
       wb_workfn+0x400/0xe60 fs/fs-writeback.c:2292
       process_one_work kernel/workqueue.c:2653 [inline]
       process_scheduled_works+0xa5d/0x15d0 kernel/workqueue.c:2730
       worker_thread+0xa55/0xfc0 kernel/workqueue.c:2811
       kthread+0x2fa/0x390 kernel/kthread.c:388
       ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
       ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293

other info that might help us debug this:

 Possible unsafe locking scenario:

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

 *** DEADLOCK ***

3 locks held by kworker/u4:5/985:
 #0: ffff88814005a138 ((wq_completion)writeback){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2628 [inline]
 #0: ffff88814005a138 ((wq_completion)writeback){+.+.}-{0:0}, at: process_scheduled_works+0x96f/0x15d0 kernel/workqueue.c:2730
 #1: ffffc90004437d00 ((work_completion)(&(&wb->dwork)->work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2628 [inline]
 #1: ffffc90004437d00 ((work_completion)(&(&wb->dwork)->work)){+.+.}-{0:0}, at: process_scheduled_works+0x96f/0x15d0 kernel/workqueue.c:2730
 #2: ffff88802cb30bd8 (&sbi->s_writepages_rwsem){++++}-{0:0}, at: ext4_writepages_down_read fs/ext4/ext4.h:1767 [inline]
 #2: ffff88802cb30bd8 (&sbi->s_writepages_rwsem){++++}-{0:0}, at: ext4_writepages+0x1a4/0x350 fs/ext4/inode.c:2806

stack backtrace:
CPU: 1 PID: 985 Comm: kworker/u4:5 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
Workqueue: writeback wb_workfn (flush-7:3)
Call Trace:
 <TASK>
 dump_stack_lvl+0x18c/0x250 lib/dump_stack.c:106
 check_noncircular+0x2fc/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+0x2df1/0x7d40 kernel/locking/lockdep.c:5137
 lock_acquire+0x19e/0x420 kernel/locking/lockdep.c:5754
 down_write+0x97/0x200 kernel/locking/rwsem.c:1573
 ext4_write_lock_xattr fs/ext4/xattr.h:158 [inline]
 ext4_destroy_inline_data+0x28/0xe0 fs/ext4/inline.c:1894
 ext4_do_writepages+0x4f0/0x3990 fs/ext4/inode.c:2604
 ext4_writepages+0x1dd/0x350 fs/ext4/inode.c:2807
 do_writepages+0x3b3/0x630 mm/page-writeback.c:2575
 __writeback_single_inode+0x153/0xec0 fs/fs-writeback.c:1635
 writeback_sb_inodes+0x7cd/0xf50 fs/fs-writeback.c:1926
 wb_writeback+0x46a/0xbf0 fs/fs-writeback.c:2105
 wb_do_writeback fs/fs-writeback.c:2252 [inline]
 wb_workfn+0x400/0xe60 fs/fs-writeback.c:2292
 process_one_work kernel/workqueue.c:2653 [inline]
 process_scheduled_works+0xa5d/0x15d0 kernel/workqueue.c:2730
 worker_thread+0xa55/0xfc0 kernel/workqueue.c:2811
 kthread+0x2fa/0x390 kernel/kthread.c:388
 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293
 </TASK>
EXT4-fs error (device loop3): ext4_mb_generate_buddy:1229: group 0, block bitmap and bg descriptor inconsistent: 25 vs 281 free clusters
EXT4-fs (loop3): Delayed block allocation failed for inode 15 at logical offset 0 with max blocks 1 with error 28
EXT4-fs (loop3): This should not happen!! Data will be lost

EXT4-fs (loop3): Total free blocks count 0
EXT4-fs (loop3): Free/Dirty block details
EXT4-fs (loop3): free_blocks=4096
EXT4-fs (loop3): dirty_blocks=496
EXT4-fs (loop3): Block reservation details
EXT4-fs (loop3): i_reserved_data_blocks=31