syzbot

======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.1.2341/14908 is trying to acquire lock:
ffff88804b0a8650 (sb_internal){.+.+}-{0:0}, at: __sb_start_write include/linux/fs.h:1811 [inline]
ffff88804b0a8650 (sb_internal){.+.+}-{0:0}, at: sb_start_intwrite include/linux/fs.h:1928 [inline]
ffff88804b0a8650 (sb_internal){.+.+}-{0:0}, at: ext4_evict_inode+0x44a/0x1090 fs/ext4/inode.c:245

but task is already holding lock:
ffff888065c6ec58 (&sbi->s_writepages_rwsem){++++}-{0:0}, at: ext4_ext_migrate+0x2d7/0xe60 fs/ext4/migrate.c:438

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+0x20f/0x2df0 fs/ext4/inode.c:2691
       do_writepages+0x476/0x6e0 mm/page-writeback.c:2386
       __writeback_single_inode+0x153/0xda0 fs/fs-writeback.c:1657
       writeback_single_inode+0x3cb/0x8e0 fs/fs-writeback.c:1770
       write_inode_now+0x23b/0x2c0 fs/fs-writeback.c:2817
       iput_final fs/inode.c:1756 [inline]
       iput+0x5ab/0x8a0 fs/inode.c:1795
       ext4_xattr_set_entry+0x34f4/0x3ea0 fs/ext4/xattr.c:1825
       ext4_xattr_block_set+0x4fd/0x2d20 fs/ext4/xattr.c:1924
       ext4_xattr_move_to_block fs/ext4/xattr.c:2618 [inline]
       ext4_xattr_make_inode_space fs/ext4/xattr.c:2693 [inline]
       ext4_expand_extra_isize_ea+0xf3f/0x19b0 fs/ext4/xattr.c:2781
       __ext4_expand_extra_isize+0x301/0x3e0 fs/ext4/inode.c:5924
       ext4_try_to_expand_extra_isize fs/ext4/inode.c:5967 [inline]
       __ext4_mark_inode_dirty+0x469/0x700 fs/ext4/inode.c:6045
       ext4_evict_inode+0xa8d/0x1090 fs/ext4/inode.c:284
       evict+0x4c9/0x8d0 fs/inode.c:647
       ext4_orphan_cleanup+0xad2/0x1320 fs/ext4/orphan.c:472
       ext4_fill_super+0x8d6e/0x94f0 fs/ext4/super.c:5006
       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+0x2e3/0x3d0 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 (sb_internal){.+.+}-{0:0}:
       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+0x2c42/0x7d10 kernel/locking/lockdep.c:5012
       lock_acquire+0x19e/0x400 kernel/locking/lockdep.c:5623
       percpu_down_read+0x46/0x1b0 include/linux/percpu-rwsem.h:51
       __sb_start_write include/linux/fs.h:1811 [inline]
       sb_start_intwrite include/linux/fs.h:1928 [inline]
       ext4_evict_inode+0x44a/0x1090 fs/ext4/inode.c:245
       evict+0x4c9/0x8d0 fs/inode.c:647
       ext4_ext_migrate+0xc0c/0xe60 fs/ext4/migrate.c:588
       __ext4_ioctl fs/ext4/ioctl.c:1031 [inline]
       ext4_ioctl+0x1a84/0x3870 fs/ext4/ioctl.c:1285
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:874 [inline]
       __se_sys_ioctl+0xfa/0x170 fs/ioctl.c:860
       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

other info that might help us debug this:

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&sbi->s_writepages_rwsem);
                               lock(sb_internal);
                               lock(&sbi->s_writepages_rwsem);
  lock(sb_internal);

 *** DEADLOCK ***

3 locks held by syz.1.2341/14908:
 #0: ffff88804b0a8460 (sb_writers#5){.+.+}-{0:0}, at: mnt_want_write_file+0x5c/0x200 fs/namespace.c:430
 #1: ffff88805a135da8 (&sb->s_type->i_mutex_key#9){++++}-{3:3}, at: inode_lock include/linux/fs.h:787 [inline]
 #1: ffff88805a135da8 (&sb->s_type->i_mutex_key#9){++++}-{3:3}, at: __ext4_ioctl fs/ext4/ioctl.c:1030 [inline]
 #1: ffff88805a135da8 (&sb->s_type->i_mutex_key#9){++++}-{3:3}, at: ext4_ioctl+0x1a7c/0x3870 fs/ext4/ioctl.c:1285
 #2: ffff888065c6ec58 (&sbi->s_writepages_rwsem){++++}-{0:0}, at: ext4_ext_migrate+0x2d7/0xe60 fs/ext4/migrate.c:438

stack backtrace:
CPU: 1 PID: 14908 Comm: syz.1.2341 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0x188/0x250 lib/dump_stack.c:106
 check_noncircular+0x296/0x330 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+0x2c42/0x7d10 kernel/locking/lockdep.c:5012
 lock_acquire+0x19e/0x400 kernel/locking/lockdep.c:5623
 percpu_down_read+0x46/0x1b0 include/linux/percpu-rwsem.h:51
 __sb_start_write include/linux/fs.h:1811 [inline]
 sb_start_intwrite include/linux/fs.h:1928 [inline]
 ext4_evict_inode+0x44a/0x1090 fs/ext4/inode.c:245
 evict+0x4c9/0x8d0 fs/inode.c:647
 ext4_ext_migrate+0xc0c/0xe60 fs/ext4/migrate.c:588
 __ext4_ioctl fs/ext4/ioctl.c:1031 [inline]
 ext4_ioctl+0x1a84/0x3870 fs/ext4/ioctl.c:1285
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:874 [inline]
 __se_sys_ioctl+0xfa/0x170 fs/ioctl.c:860
 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
RIP: 0033:0x7fd51b8f5e59
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:00007fd519b2e028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007fd51bb6f090 RCX: 00007fd51b8f5e59
RDX: 0000000000000000 RSI: 0000000000006609 RDI: 0000000000000005
RBP: 00007fd51b98bd6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fd51bb6f128 R14: 00007fd51bb6f090 R15: 00007ffe87286388
 </TASK>