syzbot

======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.2.8/4324 is trying to acquire lock:
ffff88807d860ae0 (&sdp->sd_quota_mutex){+.+.}-{3:3}, at: do_qc+0xca/0x730 fs/gfs2/quota.c:678

but task is already holding lock:
ffff88805f2b3c28 (&ip->i_rw_mutex){++++}-{3:3}, at: sweep_bh_for_rgrps fs/gfs2/bmap.c:1514 [inline]
ffff88805f2b3c28 (&ip->i_rw_mutex){++++}-{3:3}, at: punch_hole+0x23a1/0x3520 fs/gfs2/bmap.c:1839

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+0x155/0x13e0 fs/gfs2/bmap.c:858
       gfs2_iomap_get fs/gfs2/bmap.c:1398 [inline]
       gfs2_block_map+0x229/0x670 fs/gfs2/bmap.c:1213
       bh_get+0x227/0x5f0 fs/gfs2/quota.c:385
       qdsb_get+0x21c/0x3c0 fs/gfs2/quota.c:518
       gfs2_quota_hold+0x194/0x5d0 fs/gfs2/quota.c:604
       punch_hole+0xd81/0x3520 fs/gfs2/bmap.c:1800
       gfs2_iomap_end+0x4f2/0x6b0 fs/gfs2/bmap.c:1159
       iomap_iter+0x22a/0xdb0 fs/iomap/iter.c:62
       iomap_file_buffered_write+0x4e3/0x5b0 fs/iomap/buffered-io.c:814
       gfs2_file_buffered_write+0x470/0x900 fs/gfs2/file.c:1058
       gfs2_file_write_iter+0x467/0x11d0 fs/gfs2/file.c:1166
       call_write_iter include/linux/fs.h:2172 [inline]
       new_sync_write fs/read_write.c:507 [inline]
       vfs_write+0x712/0xd00 fs/read_write.c:594
       ksys_write+0x14d/0x250 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+0x2c33/0x7c60 kernel/locking/lockdep.c:5012
       lock_acquire+0x197/0x3f0 kernel/locking/lockdep.c:5623
       __mutex_lock_common+0x1eb/0x2390 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
       punch_hole+0x2f8b/0x3520 fs/gfs2/bmap.c:1940
       gfs2_iomap_end+0x4f2/0x6b0 fs/gfs2/bmap.c:1159
       iomap_iter+0x22a/0xdb0 fs/iomap/iter.c:62
       iomap_file_buffered_write+0x4e3/0x5b0 fs/iomap/buffered-io.c:814
       gfs2_file_buffered_write+0x470/0x900 fs/gfs2/file.c:1058
       gfs2_file_write_iter+0x467/0x11d0 fs/gfs2/file.c:1166
       call_write_iter include/linux/fs.h:2172 [inline]
       new_sync_write fs/read_write.c:507 [inline]
       vfs_write+0x712/0xd00 fs/read_write.c:594
       ksys_write+0x14d/0x250 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.2.8/4324:
 #0: ffff8880231df770 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x2bf/0x370 fs/file.c:1056
 #1: ffff888079a8a460 (sb_writers#16){.+.+}-{0:0}, at: vfs_write+0x28a/0xd00 fs/read_write.c:590
 #2: ffff88805f2b3790 (&sb->s_type->i_mutex_key#25){+.+.}-{3:3}, at: inode_lock include/linux/fs.h:787 [inline]
 #2: ffff88805f2b3790 (&sb->s_type->i_mutex_key#25){+.+.}-{3:3}, at: gfs2_file_write_iter+0x33b/0x11d0 fs/gfs2/file.c:1123
 #3: ffff888079a8a650 (sb_internal#3){.+.+}-{0:0}, at: gfs2_trans_begin+0x6b/0xe0 fs/gfs2/trans.c:118
 #4: ffff88807d8610a8 (&sdp->sd_log_flush_lock){.+.+}-{3:3}, at: __gfs2_trans_begin+0x50f/0x880 fs/gfs2/trans.c:87
 #5: ffff88805f2b3c28 (&ip->i_rw_mutex){++++}-{3:3}, at: sweep_bh_for_rgrps fs/gfs2/bmap.c:1514 [inline]
 #5: ffff88805f2b3c28 (&ip->i_rw_mutex){++++}-{3:3}, at: punch_hole+0x23a1/0x3520 fs/gfs2/bmap.c:1839

stack backtrace:
CPU: 0 PID: 4324 Comm: syz.2.8 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
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
 __mutex_lock_common+0x1eb/0x2390 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
 punch_hole+0x2f8b/0x3520 fs/gfs2/bmap.c:1940
 gfs2_iomap_end+0x4f2/0x6b0 fs/gfs2/bmap.c:1159
 iomap_iter+0x22a/0xdb0 fs/iomap/iter.c:62
 iomap_file_buffered_write+0x4e3/0x5b0 fs/iomap/buffered-io.c:814
 gfs2_file_buffered_write+0x470/0x900 fs/gfs2/file.c:1058
 gfs2_file_write_iter+0x467/0x11d0 fs/gfs2/file.c:1166
 call_write_iter include/linux/fs.h:2172 [inline]
 new_sync_write fs/read_write.c:507 [inline]
 vfs_write+0x712/0xd00 fs/read_write.c:594
 ksys_write+0x14d/0x250 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: 0033:0x7f6cac491ba9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f6caa6f9038 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f6cac6d8fa0 RCX: 00007f6cac491ba9
RDX: 000000006db6e559 RSI: 0000200000000180 RDI: 0000000000000004
RBP: 00007f6cac514e19 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f6cac6d9038 R14: 00007f6cac6d8fa0 R15: 00007ffccc507cd8
 </TASK>