syzbot

EXT4-fs (loop0): mounted filesystem 00000000-0000-0000-0000-000000000000 r/w without journal. Quota mode: none.
EXT4-fs error (device loop0): ext4_mb_generate_buddy:1317: group 0, block bitmap and bg descriptor inconsistent: 25 vs 1305 free clusters
======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.0.22/5956 is trying to acquire lock:
ffff88805b2fc7c8 (&ei->xattr_sem){++++}-{4:4}, at: ext4_write_lock_xattr fs/ext4/xattr.h:157 [inline]
ffff88805b2fc7c8 (&ei->xattr_sem){++++}-{4:4}, at: ext4_destroy_inline_data+0x28/0xe0 fs/ext4/inline.c:1805

but task is already holding lock:
ffff888037f34cd8 (&sbi->s_writepages_rwsem){++++}-{0:0}, at: percpu_down_read include/linux/percpu-rwsem.h:77 [inline]
ffff888037f34cd8 (&sbi->s_writepages_rwsem){++++}-{0:0}, at: ext4_writepages_down_read fs/ext4/ext4.h:1876 [inline]
ffff888037f34cd8 (&sbi->s_writepages_rwsem){++++}-{0:0}, at: ext4_writepages+0x205/0x3b0 fs/ext4/inode.c:3042

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_internal+0x48/0x1d0 include/linux/percpu-rwsem.h:53
       percpu_down_read include/linux/percpu-rwsem.h:77 [inline]
       ext4_writepages_down_read fs/ext4/ext4.h:1876 [inline]
       ext4_writepages+0x205/0x3b0 fs/ext4/inode.c:3042
       do_writepages+0x338/0x560 mm/page-writeback.c:2571
       __writeback_single_inode+0x12e/0xf90 fs/fs-writeback.c:1787
       writeback_single_inode+0x4dd/0xe10 fs/fs-writeback.c:1906
       write_inode_now+0x1c2/0x290 fs/fs-writeback.c:3060
       iput_final fs/inode.c:2009 [inline]
       iput+0x98b/0xf00 fs/inode.c:2068
       ext4_xattr_block_set+0x22e4/0x2a80 fs/ext4/xattr.c:2153
       ext4_xattr_move_to_block fs/ext4/xattr.c:2671 [inline]
       ext4_xattr_make_inode_space fs/ext4/xattr.c:2746 [inline]
       ext4_expand_extra_isize_ea+0x1342/0x1e70 fs/ext4/xattr.c:2834
       __ext4_expand_extra_isize+0x30d/0x400 fs/ext4/inode.c:6486
       ext4_try_to_expand_extra_isize fs/ext4/inode.c:6529 [inline]
       __ext4_mark_inode_dirty+0x455/0x700 fs/ext4/inode.c:6607
       ext4_evict_inode+0x976/0x10c0 fs/ext4/inode.c:267
       evict+0x624/0xb50 fs/inode.c:825
       ext4_orphan_cleanup+0xc7a/0x14c0 fs/ext4/orphan.c:472
       __ext4_fill_super fs/ext4/super.c:5705 [inline]
       ext4_fill_super+0x5cc0/0x65d0 fs/ext4/super.c:5828
       get_tree_bdev_flags+0x430/0x4f0 fs/super.c:1634
       vfs_get_tree+0x92/0x2a0 fs/super.c:1694
       fc_mount fs/namespace.c:1198 [inline]
       do_new_mount_fc fs/namespace.c:3765 [inline]
       do_new_mount+0x319/0xdc0 fs/namespace.c:3841
       do_mount fs/namespace.c:4174 [inline]
       __do_sys_mount fs/namespace.c:4390 [inline]
       __se_sys_mount+0x31d/0x420 fs/namespace.c:4367
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (&ei->xattr_sem){++++}-{4:4}:
       check_prev_add kernel/locking/lockdep.c:3165 [inline]
       check_prevs_add kernel/locking/lockdep.c:3284 [inline]
       validate_chain kernel/locking/lockdep.c:3908 [inline]
       __lock_acquire+0x1520/0x2ce0 kernel/locking/lockdep.c:5237
       lock_acquire+0x106/0x350 kernel/locking/lockdep.c:5868
       down_write+0x3a/0x50 kernel/locking/rwsem.c:1631
       ext4_write_lock_xattr fs/ext4/xattr.h:157 [inline]
       ext4_destroy_inline_data+0x28/0xe0 fs/ext4/inline.c:1805
       ext4_do_writepages+0x576/0x47a0 fs/ext4/inode.c:2828
       ext4_writepages+0x241/0x3b0 fs/ext4/inode.c:3043
       do_writepages+0x338/0x560 mm/page-writeback.c:2571
       filemap_writeback mm/filemap.c:387 [inline]
       filemap_fdatawrite_range mm/filemap.c:412 [inline]
       file_write_and_wait_range+0x374/0x440 mm/filemap.c:786
       mmb_fsync_noflush+0x76/0x1d0 fs/buffer.c:652
       ext4_fsync_nojournal fs/ext4/fsync.c:92 [inline]
       ext4_sync_file+0x423/0xd10 fs/ext4/fsync.c:160
       generic_write_sync include/linux/fs.h:2666 [inline]
       ext4_buffered_write_iter+0x2ca/0x370 fs/ext4/file.c:322
       ext4_file_write_iter+0x94b/0x1c90 fs/ext4/file.c:-1
       do_iter_readv_writev+0x624/0x8d0 fs/read_write.c:-1
       vfs_writev+0x34c/0x990 fs/read_write.c:1058
       do_pwritev fs/read_write.c:1154 [inline]
       __do_sys_pwritev2 fs/read_write.c:1212 [inline]
       __se_sys_pwritev2+0x17a/0x2a0 fs/read_write.c:1203
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

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 ***

2 locks held by syz.0.22/5956:
 #0: ffff88803ccca500 (sb_writers#4){.+.+}-{0:0}, at: file_start_write include/linux/fs.h:2733 [inline]
 #0: ffff88803ccca500 (sb_writers#4){.+.+}-{0:0}, at: vfs_writev+0x2b5/0x990 fs/read_write.c:1056
 #1: ffff888037f34cd8 (&sbi->s_writepages_rwsem){++++}-{0:0}, at: percpu_down_read include/linux/percpu-rwsem.h:77 [inline]
 #1: ffff888037f34cd8 (&sbi->s_writepages_rwsem){++++}-{0:0}, at: ext4_writepages_down_read fs/ext4/ext4.h:1876 [inline]
 #1: ffff888037f34cd8 (&sbi->s_writepages_rwsem){++++}-{0:0}, at: ext4_writepages+0x205/0x3b0 fs/ext4/inode.c:3042

stack backtrace:
CPU: 1 UID: 0 PID: 5956 Comm: syz.0.22 Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 print_circular_bug+0x2e1/0x300 kernel/locking/lockdep.c:2043
 check_noncircular+0x12e/0x150 kernel/locking/lockdep.c:2175
 check_prev_add kernel/locking/lockdep.c:3165 [inline]
 check_prevs_add kernel/locking/lockdep.c:3284 [inline]
 validate_chain kernel/locking/lockdep.c:3908 [inline]
 __lock_acquire+0x1520/0x2ce0 kernel/locking/lockdep.c:5237
 lock_acquire+0x106/0x350 kernel/locking/lockdep.c:5868
 down_write+0x3a/0x50 kernel/locking/rwsem.c:1631
 ext4_write_lock_xattr fs/ext4/xattr.h:157 [inline]
 ext4_destroy_inline_data+0x28/0xe0 fs/ext4/inline.c:1805
 ext4_do_writepages+0x576/0x47a0 fs/ext4/inode.c:2828
 ext4_writepages+0x241/0x3b0 fs/ext4/inode.c:3043
 do_writepages+0x338/0x560 mm/page-writeback.c:2571
 filemap_writeback mm/filemap.c:387 [inline]
 filemap_fdatawrite_range mm/filemap.c:412 [inline]
 file_write_and_wait_range+0x374/0x440 mm/filemap.c:786
 mmb_fsync_noflush+0x76/0x1d0 fs/buffer.c:652
 ext4_fsync_nojournal fs/ext4/fsync.c:92 [inline]
 ext4_sync_file+0x423/0xd10 fs/ext4/fsync.c:160
 generic_write_sync include/linux/fs.h:2666 [inline]
 ext4_buffered_write_iter+0x2ca/0x370 fs/ext4/file.c:322
 ext4_file_write_iter+0x94b/0x1c90 fs/ext4/file.c:-1
 do_iter_readv_writev+0x624/0x8d0 fs/read_write.c:-1
 vfs_writev+0x34c/0x990 fs/read_write.c:1058
 do_pwritev fs/read_write.c:1154 [inline]
 __do_sys_pwritev2 fs/read_write.c:1212 [inline]
 __se_sys_pwritev2+0x17a/0x2a0 fs/read_write.c:1203
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f2e5251de59
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffd1b97f6a8 EFLAGS: 00000246 ORIG_RAX: 0000000000000148
RAX: ffffffffffffffda RBX: 00007f2e527a5fa0 RCX: 00007f2e5251de59
RDX: 0000000000000001 RSI: 0000200000000140 RDI: 0000000000000004
RBP: 00007f2e525b3e6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000e7b R11: 0000000000000246 R12: 0000000000000000
R13: 00007f2e527a5fac R14: 00007f2e527a5fa0 R15: 00007f2e527a5fa0
 </TASK>
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=20480
EXT4-fs (loop0): dirty_blocks=16
EXT4-fs (loop0): Block reservation details
EXT4-fs (loop0): i_reserved_data_blocks=1