syzbot

======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.2.15/4405 is trying to acquire lock:
ffff888077e90ae0 (&sdp->sd_quota_mutex){+.+.}-{3:3}, at: do_qc+0xca/0x730 fs/gfs2/quota.c:678

but task is already holding lock:
ffff88805f7505e8 (&ip->i_rw_mutex){++++}-{3:3}, at: __gfs2_iomap_alloc+0x286/0x1a30 fs/gfs2/bmap.c:687

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (&ip->i_rw_mutex){++++}-{3:3}:
       down_read+0x44/0x2e0 kernel/locking/rwsem.c:1498
       __gfs2_iomap_get+0x15b/0x1400 fs/gfs2/bmap.c:864
       gfs2_iomap_get fs/gfs2/bmap.c:1415 [inline]
       gfs2_block_map+0x2a0/0x740 fs/gfs2/bmap.c:1230
       bh_get+0x275/0x650 fs/gfs2/quota.c:385
       qdsb_get+0x21c/0x3c0 fs/gfs2/quota.c:518
       gfs2_quota_hold+0x194/0x5d0 fs/gfs2/quota.c:604
       gfs2_quota_lock+0xa0/0x7d0 fs/gfs2/quota.c:1076
       gfs2_quota_lock_check fs/gfs2/quota.h:50 [inline]
       gfs2_iomap_begin_write fs/gfs2/bmap.c:1021 [inline]
       gfs2_iomap_begin+0x76c/0x13b0 fs/gfs2/bmap.c:1120
       iomap_iter+0x620/0xdb0 fs/iomap/iter.c:74
       iomap_file_buffered_write+0x1bb/0x630 fs/iomap/buffered-io.c:814
       gfs2_file_buffered_write+0x470/0x900 fs/gfs2/file.c:1058
       gfs2_file_write_iter+0x497/0x1240 fs/gfs2/file.c:1166
       call_write_iter include/linux/fs.h:2173 [inline]
       new_sync_write fs/read_write.c:507 [inline]
       vfs_write+0x745/0xd60 fs/read_write.c:594
       ksys_write+0x152/0x260 fs/read_write.c:647
       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 (&sdp->sd_quota_mutex){+.+.}-{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+0x2c42/0x7d10 kernel/locking/lockdep.c:5012
       lock_acquire+0x19e/0x400 kernel/locking/lockdep.c:5623
       __mutex_lock_common+0x1e3/0x2400 kernel/locking/mutex.c:596
       __mutex_lock kernel/locking/mutex.c:729 [inline]
       mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:743
       do_qc+0xca/0x730 fs/gfs2/quota.c:678
       gfs2_quota_change+0x2f5/0x8e0 fs/gfs2/quota.c:1295
       gfs2_alloc_blocks+0x196c/0x2120 fs/gfs2/rgrp.c:2504
       __gfs2_iomap_alloc+0x4de/0x1a30 fs/gfs2/bmap.c:713
       gfs2_iomap_begin_write fs/gfs2/bmap.c:1055 [inline]
       gfs2_iomap_begin+0xcb2/0x13b0 fs/gfs2/bmap.c:1120
       iomap_iter+0x620/0xdb0 fs/iomap/iter.c:74
       iomap_file_buffered_write+0x1bb/0x630 fs/iomap/buffered-io.c:814
       gfs2_file_buffered_write+0x470/0x900 fs/gfs2/file.c:1058
       gfs2_file_write_iter+0x497/0x1240 fs/gfs2/file.c:1166
       call_write_iter include/linux/fs.h:2173 [inline]
       new_sync_write fs/read_write.c:507 [inline]
       vfs_write+0x745/0xd60 fs/read_write.c:594
       ksys_write+0x152/0x260 fs/read_write.c:647
       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(&ip->i_rw_mutex);
                               lock(&sdp->sd_quota_mutex);
                               lock(&ip->i_rw_mutex);
  lock(&sdp->sd_quota_mutex);

 *** DEADLOCK ***

6 locks held by syz.2.15/4405:
 #0: ffff888077d2e5f0 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x2bf/0x370 fs/file.c:1056
 #1: ffff88814760e460 (sb_writers#18){.+.+}-{0:0}, at: vfs_write+0x295/0xd60 fs/read_write.c:590
 #2: ffff88805f750150 (&sb->s_type->i_mutex_key#25){+.+.}-{3:3}, at: inode_lock include/linux/fs.h:787 [inline]
 #2: ffff88805f750150 (&sb->s_type->i_mutex_key#25){+.+.}-{3:3}, at: gfs2_file_write_iter+0x35e/0x1240 fs/gfs2/file.c:1123
 #3: ffff88814760e650 (sb_internal#5){.+.+}-{0:0}, at: gfs2_trans_begin+0x6b/0xe0 fs/gfs2/trans.c:118
 #4: ffff888077e910a8 (&sdp->sd_log_flush_lock){.+.+}-{3:3}, at: __gfs2_trans_begin+0x515/0x890 fs/gfs2/trans.c:87
 #5: ffff88805f7505e8 (&ip->i_rw_mutex){++++}-{3:3}, at: __gfs2_iomap_alloc+0x286/0x1a30 fs/gfs2/bmap.c:687

stack backtrace:
CPU: 1 PID: 4405 Comm: syz.2.15 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
 __mutex_lock_common+0x1e3/0x2400 kernel/locking/mutex.c:596
 __mutex_lock kernel/locking/mutex.c:729 [inline]
 mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:743
 do_qc+0xca/0x730 fs/gfs2/quota.c:678
 gfs2_quota_change+0x2f5/0x8e0 fs/gfs2/quota.c:1295
 gfs2_alloc_blocks+0x196c/0x2120 fs/gfs2/rgrp.c:2504
 __gfs2_iomap_alloc+0x4de/0x1a30 fs/gfs2/bmap.c:713
 gfs2_iomap_begin_write fs/gfs2/bmap.c:1055 [inline]
 gfs2_iomap_begin+0xcb2/0x13b0 fs/gfs2/bmap.c:1120
 iomap_iter+0x620/0xdb0 fs/iomap/iter.c:74
 iomap_file_buffered_write+0x1bb/0x630 fs/iomap/buffered-io.c:814
 gfs2_file_buffered_write+0x470/0x900 fs/gfs2/file.c:1058
 gfs2_file_write_iter+0x497/0x1240 fs/gfs2/file.c:1166
 call_write_iter include/linux/fs.h:2173 [inline]
 new_sync_write fs/read_write.c:507 [inline]
 vfs_write+0x745/0xd60 fs/read_write.c:594
 ksys_write+0x152/0x260 fs/read_write.c:647
 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: 0033:0x7f1fa2cdbe59
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:00007f1fa0f14028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f1fa2f55090 RCX: 00007f1fa2cdbe59
RDX: 00000000fffffceb RSI: 00002000000001c0 RDI: 0000000000000004
RBP: 00007f1fa2d71d6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f1fa2f55128 R14: 00007f1fa2f55090 R15: 00007ffd981fc2a8
 </TASK>