syzbot

======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.2.241/5239 is trying to acquire lock:
ffff888073814ae0 (&sdp->sd_quota_mutex){+.+.}-{3:3}, at: do_qc+0xca/0x730 fs/gfs2/quota.c:678

but task is already holding lock:
ffff888056045080 (&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]
       alloc_dinode+0x173/0x500 fs/gfs2/inode.c:402
       gfs2_create_inode+0xcca/0x1460 fs/gfs2/inode.c:721
       gfs2_atomic_open+0xce/0x210 fs/gfs2/inode.c:1296
       atomic_open fs/namei.c:3333 [inline]
       lookup_open fs/namei.c:3441 [inline]
       open_last_lookups fs/namei.c:3540 [inline]
       path_openat+0xe8c/0x2fa0 fs/namei.c:3747
       do_filp_open+0x1e2/0x410 fs/namei.c:3777
       do_sys_openat2+0x150/0x4b0 fs/open.c:1255
       do_sys_open fs/open.c:1271 [inline]
       __do_sys_open fs/open.c:1279 [inline]
       __se_sys_open fs/open.c:1275 [inline]
       __x64_sys_open+0x11b/0x140 fs/open.c:1275
       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+0xfaf/0x1240 fs/gfs2/file.c:1145
       do_iter_readv_writev+0x47e/0x5f0 fs/read_write.c:-1
       do_iter_write+0x205/0x7b0 fs/read_write.c:855
       vfs_writev fs/read_write.c:928 [inline]
       do_pwritev+0x240/0x3a0 fs/read_write.c:1025
       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 ***

5 locks held by syz.2.241/5239:
 #0: ffff888079488460 (sb_writers#28){.+.+}-{0:0}, at: vfs_writev fs/read_write.c:927 [inline]
 #0: ffff888079488460 (sb_writers#28){.+.+}-{0:0}, at: do_pwritev+0x229/0x3a0 fs/read_write.c:1025
 #1: ffff888056044be8 (&sb->s_type->i_mutex_key#33){+.+.}-{3:3}, at: inode_lock include/linux/fs.h:787 [inline]
 #1: ffff888056044be8 (&sb->s_type->i_mutex_key#33){+.+.}-{3:3}, at: gfs2_file_write_iter+0x35e/0x1240 fs/gfs2/file.c:1123
 #2: ffff888079488650 (sb_internal#4){.+.+}-{0:0}, at: gfs2_trans_begin+0x6b/0xe0 fs/gfs2/trans.c:118
 #3: ffff8880738150a8 (&sdp->sd_log_flush_lock){.+.+}-{3:3}, at: __gfs2_trans_begin+0x515/0x890 fs/gfs2/trans.c:87
 #4: ffff888056045080 (&ip->i_rw_mutex){++++}-{3:3}, at: __gfs2_iomap_alloc+0x286/0x1a30 fs/gfs2/bmap.c:687

stack backtrace:
CPU: 1 PID: 5239 Comm: syz.2.241 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+0xfaf/0x1240 fs/gfs2/file.c:1145
 do_iter_readv_writev+0x47e/0x5f0 fs/read_write.c:-1
 do_iter_write+0x205/0x7b0 fs/read_write.c:855
 vfs_writev fs/read_write.c:928 [inline]
 do_pwritev+0x240/0x3a0 fs/read_write.c:1025
 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: 0033:0x7fe6fcd93dd9
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:00007fe6fafed028 EFLAGS: 00000246 ORIG_RAX: 0000000000000148
RAX: ffffffffffffffda RBX: 00007fe6fd00cfa0 RCX: 00007fe6fcd93dd9
RDX: 0000000000000001 RSI: 0000200000000240 RDI: 0000000000000004
RBP: 00007fe6fce29d69 R08: 0000000000000000 R09: 0000000000000003
R10: 0000000000002000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fe6fd00d038 R14: 00007fe6fd00cfa0 R15: 00007fffbd1ef128
 </TASK>