syzbot

======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.0.570/8109 is trying to acquire lock:
ffff888030db4ae8 (&sdp->sd_quota_mutex){+.+.}-{3:3}, at: do_qc+0xaf/0x670 fs/gfs2/quota.c:689

but task is already holding lock:
ffff88805b015688 (&ip->i_rw_mutex){++++}-{3:3}, at: __gfs2_iomap_alloc+0x278/0x1a10 fs/gfs2/bmap.c:679

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+0x46/0x2e0 kernel/locking/rwsem.c:1520
       __gfs2_iomap_get+0x159/0x13f0 fs/gfs2/bmap.c:856
       gfs2_iomap_get+0xc5/0x120 fs/gfs2/bmap.c:1410
       bh_get+0x225/0x710 fs/gfs2/quota.c:401
       qdsb_get+0x210/0x330 fs/gfs2/quota.c:535
       gfs2_quota_hold+0x198/0x5e0 fs/gfs2/quota.c:615
       gfs2_quota_lock+0xba/0x7b0 fs/gfs2/quota.c:1070
       gfs2_quota_lock_check fs/gfs2/quota.h:50 [inline]
       alloc_dinode+0x169/0x580 fs/gfs2/inode.c:409
       gfs2_create_inode+0xcb4/0x1430 fs/gfs2/inode.c:739
       gfs2_atomic_open+0xd2/0x220 fs/gfs2/inode.c:1315
       atomic_open fs/namei.c:3351 [inline]
       lookup_open fs/namei.c:3459 [inline]
       open_last_lookups fs/namei.c:3556 [inline]
       path_openat+0xf27/0x3190 fs/namei.c:3786
       do_filp_open+0x1c5/0x3d0 fs/namei.c:3816
       do_sys_openat2+0x12c/0x1c0 fs/open.c:1419
       do_sys_open fs/open.c:1434 [inline]
       __do_sys_openat fs/open.c:1450 [inline]
       __se_sys_openat fs/open.c:1445 [inline]
       __x64_sys_openat+0x139/0x160 fs/open.c:1445
       do_syscall_x64 arch/x86/entry/common.c:51 [inline]
       do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
       entry_SYSCALL_64_after_hwframe+0x68/0xd2

-> #0 (&sdp->sd_quota_mutex){+.+.}-{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+0x2ddb/0x7c80 kernel/locking/lockdep.c:5137
       lock_acquire+0x197/0x410 kernel/locking/lockdep.c:5754
       __mutex_lock_common kernel/locking/mutex.c:603 [inline]
       __mutex_lock+0x129/0xcc0 kernel/locking/mutex.c:747
       do_qc+0xaf/0x670 fs/gfs2/quota.c:689
       gfs2_quota_change+0x2b9/0x800 fs/gfs2/quota.c:1289
       gfs2_alloc_blocks+0x18a8/0x2060 fs/gfs2/rgrp.c:2496
       __gfs2_iomap_alloc+0x4b8/0x1a10 fs/gfs2/bmap.c:705
       gfs2_iomap_begin_write fs/gfs2/bmap.c:1061 [inline]
       gfs2_iomap_begin+0xacf/0x1260 fs/gfs2/bmap.c:1126
       iomap_iter+0x6b1/0xec0 fs/iomap/iter.c:91
       iomap_file_buffered_write+0x1b5/0xd10 fs/iomap/buffered-io.c:974
       gfs2_file_buffered_write+0x4bd/0x820 fs/gfs2/file.c:1060
       gfs2_file_write_iter+0xb6e/0xe10 fs/gfs2/file.c:1137
       do_iter_readv_writev fs/read_write.c:-1 [inline]
       do_iter_write+0x79a/0xc70 fs/read_write.c:860
       iter_file_splice_write+0x66f/0xc50 fs/splice.c:736
       do_splice_from fs/splice.c:933 [inline]
       direct_splice_actor+0xe8/0x130 fs/splice.c:1142
       splice_direct_to_actor+0x2f0/0x870 fs/splice.c:1088
       do_splice_direct+0x1b7/0x2c0 fs/splice.c:1194
       do_sendfile+0x5dc/0xf70 fs/read_write.c:1254
       __do_sys_sendfile64 fs/read_write.c:1322 [inline]
       __se_sys_sendfile64+0x13f/0x190 fs/read_write.c:1308
       do_syscall_x64 arch/x86/entry/common.c:51 [inline]
       do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
       entry_SYSCALL_64_after_hwframe+0x68/0xd2

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 ***

5 locks held by syz.0.570/8109:
 #0: ffff88802556c418 (sb_writers#28){.+.+}-{0:0}, at: do_sendfile+0x5b9/0xf70 fs/read_write.c:1253
 #1: ffff88805b015200 (&sb->s_type->i_mutex_key#32){+.+.}-{3:3}, at: inode_lock include/linux/fs.h:804 [inline]
 #1: ffff88805b015200 (&sb->s_type->i_mutex_key#32){+.+.}-{3:3}, at: gfs2_file_write_iter+0x304/0xe10 fs/gfs2/file.c:1115
 #2: ffff88802556c608 (sb_internal#6){.+.+}-{0:0}, at: gfs2_trans_begin+0x6f/0xe0 fs/gfs2/trans.c:118
 #3: ffff888030db5060 (&sdp->sd_log_flush_lock){.+.+}-{3:3}, at: __gfs2_trans_begin+0x511/0x880 fs/gfs2/trans.c:87
 #4: ffff88805b015688 (&ip->i_rw_mutex){++++}-{3:3}, at: __gfs2_iomap_alloc+0x278/0x1a10 fs/gfs2/bmap.c:679

stack backtrace:
CPU: 0 PID: 8109 Comm: syz.0.570 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x16c/0x230 lib/dump_stack.c:106
 check_noncircular+0x2bd/0x3c0 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+0x2ddb/0x7c80 kernel/locking/lockdep.c:5137
 lock_acquire+0x197/0x410 kernel/locking/lockdep.c:5754
 __mutex_lock_common kernel/locking/mutex.c:603 [inline]
 __mutex_lock+0x129/0xcc0 kernel/locking/mutex.c:747
 do_qc+0xaf/0x670 fs/gfs2/quota.c:689
 gfs2_quota_change+0x2b9/0x800 fs/gfs2/quota.c:1289
 gfs2_alloc_blocks+0x18a8/0x2060 fs/gfs2/rgrp.c:2496
 __gfs2_iomap_alloc+0x4b8/0x1a10 fs/gfs2/bmap.c:705
 gfs2_iomap_begin_write fs/gfs2/bmap.c:1061 [inline]
 gfs2_iomap_begin+0xacf/0x1260 fs/gfs2/bmap.c:1126
 iomap_iter+0x6b1/0xec0 fs/iomap/iter.c:91
 iomap_file_buffered_write+0x1b5/0xd10 fs/iomap/buffered-io.c:974
 gfs2_file_buffered_write+0x4bd/0x820 fs/gfs2/file.c:1060
 gfs2_file_write_iter+0xb6e/0xe10 fs/gfs2/file.c:1137
 do_iter_readv_writev fs/read_write.c:-1 [inline]
 do_iter_write+0x79a/0xc70 fs/read_write.c:860
 iter_file_splice_write+0x66f/0xc50 fs/splice.c:736
 do_splice_from fs/splice.c:933 [inline]
 direct_splice_actor+0xe8/0x130 fs/splice.c:1142
 splice_direct_to_actor+0x2f0/0x870 fs/splice.c:1088
 do_splice_direct+0x1b7/0x2c0 fs/splice.c:1194
 do_sendfile+0x5dc/0xf70 fs/read_write.c:1254
 __do_sys_sendfile64 fs/read_write.c:1322 [inline]
 __se_sys_sendfile64+0x13f/0x190 fs/read_write.c:1308
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fe3b258ebe9
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:00007fe3b341d038 EFLAGS: 00000246 ORIG_RAX: 0000000000000028
RAX: ffffffffffffffda RBX: 00007fe3b27c5fa0 RCX: 00007fe3b258ebe9
RDX: 0000000000000000 RSI: 0000000000000009 RDI: 0000000000000008
RBP: 00007fe3b2611e19 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000020fffe82 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fe3b27c6038 R14: 00007fe3b27c5fa0 R15: 00007ffc05627168
 </TASK>