[syzbot] [gfs2?] possible deadlock in gfs2_trans_begin (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: cd5a0afbdf80 Merge tag 'mailbox-v6.18' of git://git.kernel..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=14d3852f980000
kernel config: https://syzkaller.appspot.com/x/.config?x=5b213914b883d014
dashboard link: https://syzkaller.appspot.com/bug?extid=68c035f26b00b18d07d1
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-cd5a0afb.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/67f9eda6483e/vmlinux-cd5a0afb.xz
kernel image: https://storage.googleapis.com/syzbot-assets/5368c61451e5/bzImage-cd5a0afb.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+68c035...@syzkaller.appspotmail.com

======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
kswapd0/78 is trying to acquire lock:
ffff8880332bc610 (sb_internal#2){.+.+}-{0:0}, at: gfs2_trans_begin+0x6f/0xe0 fs/gfs2/trans.c:118

but task is already holding lock:
ffffffff8e247a40 (fs_reclaim){+.+.}-{0:0}, at: balance_pgdat mm/vmscan.c:7015 [inline]
ffffffff8e247a40 (fs_reclaim){+.+.}-{0:0}, at: kswapd+0x951/0x2800 mm/vmscan.c:7389

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #3 (fs_reclaim){+.+.}-{0:0}:
lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868
__fs_reclaim_acquire mm/page_alloc.c:4269 [inline]
fs_reclaim_acquire+0x72/0x100 mm/page_alloc.c:4283
might_alloc include/linux/sched/mm.h:318 [inline]
prepare_alloc_pages+0x153/0x610 mm/page_alloc.c:4951
__alloc_frozen_pages_noprof+0x123/0x370 mm/page_alloc.c:5172
alloc_pages_mpol+0x232/0x4a0 mm/mempolicy.c:2416
alloc_frozen_pages_noprof mm/mempolicy.c:2487 [inline]
alloc_pages_noprof+0xa9/0x190 mm/mempolicy.c:2507
folio_alloc_noprof+0x1e/0x30 mm/mempolicy.c:2517
filemap_alloc_folio_noprof+0xdf/0x470 mm/filemap.c:1020
__filemap_get_folio+0x3f2/0xaf0 mm/filemap.c:2012
filemap_grab_folio include/linux/pagemap.h:838 [inline]
gfs2_unstuff_dinode+0xe8/0x1320 fs/gfs2/bmap.c:162
gfs2_iomap_begin_write fs/gfs2/bmap.c:1059 [inline]
gfs2_iomap_begin+0x9a7/0x11c0 fs/gfs2/bmap.c:1133
iomap_iter+0x534/0xde0 fs/iomap/iter.c:108
iomap_file_buffered_write+0x207/0x9b0 fs/iomap/buffered-io.c:1070
gfs2_file_buffered_write+0x4ed/0x880 fs/gfs2/file.c:1061
gfs2_file_write_iter+0x94e/0x1100 fs/gfs2/file.c:1166
new_sync_write fs/read_write.c:593 [inline]
vfs_write+0x5c6/0xb30 fs/read_write.c:686
ksys_write+0x145/0x250 fs/read_write.c:738
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #2 (&ip->i_rw_mutex){++++}-{4:4}:
lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868
down_write+0x96/0x1f0 kernel/locking/rwsem.c:1590
gfs2_unstuff_dinode+0x9d/0x1320 fs/gfs2/bmap.c:161
gfs2_iomap_begin_write fs/gfs2/bmap.c:1059 [inline]
gfs2_iomap_begin+0x9a7/0x11c0 fs/gfs2/bmap.c:1133
iomap_iter+0x534/0xde0 fs/iomap/iter.c:108
iomap_file_buffered_write+0x207/0x9b0 fs/iomap/buffered-io.c:1070
gfs2_file_buffered_write+0x4ed/0x880 fs/gfs2/file.c:1061
gfs2_file_write_iter+0x94e/0x1100 fs/gfs2/file.c:1166
new_sync_write fs/read_write.c:593 [inline]
vfs_write+0x5c6/0xb30 fs/read_write.c:686
ksys_write+0x145/0x250 fs/read_write.c:738
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #1 (&sdp->sd_log_flush_lock){++++}-{4:4}:
lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868
down_read+0x46/0x2e0 kernel/locking/rwsem.c:1537
__gfs2_trans_begin+0x515/0x890 fs/gfs2/trans.c:87
gfs2_trans_begin+0x6f/0xe0 fs/gfs2/trans.c:118
alloc_dinode+0x1e7/0x550 fs/gfs2/inode.c:418
gfs2_create_inode+0xbbc/0x1560 fs/gfs2/inode.c:807
gfs2_atomic_open+0x116/0x200 fs/gfs2/inode.c:1387
atomic_open fs/namei.c:3656 [inline]
lookup_open fs/namei.c:3767 [inline]
open_last_lookups fs/namei.c:3895 [inline]
path_openat+0xf63/0x3830 fs/namei.c:4131
do_filp_open+0x1fa/0x410 fs/namei.c:4161
do_sys_openat2+0x121/0x1c0 fs/open.c:1437
do_sys_open fs/open.c:1452 [inline]
__do_sys_openat fs/open.c:1468 [inline]
__se_sys_openat fs/open.c:1463 [inline]
__x64_sys_openat+0x138/0x170 fs/open.c:1463
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (sb_internal#2){.+.+}-{0:0}:
check_prev_add kernel/locking/lockdep.c:3165 [inline]
check_prevs_add kernel/locking/lockdep.c:3284 [inline]
validate_chain+0xb9b/0x2140 kernel/locking/lockdep.c:3908
__lock_acquire+0xab9/0xd20 kernel/locking/lockdep.c:5237
lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868
percpu_down_read_internal include/linux/percpu-rwsem.h:53 [inline]
percpu_down_read_freezable include/linux/percpu-rwsem.h:83 [inline]
__sb_start_write include/linux/fs.h:1916 [inline]
sb_start_intwrite include/linux/fs.h:2099 [inline]
__gfs2_trans_begin+0x42a/0x890 fs/gfs2/trans.c:76
gfs2_trans_begin+0x6f/0xe0 fs/gfs2/trans.c:118
gfs2_dirty_inode+0x3cb/0x600 fs/gfs2/super.c:508
__mark_inode_dirty+0x2ec/0xe10 fs/fs-writeback.c:2566
mark_inode_dirty_sync include/linux/fs.h:2619 [inline]
iput+0x381/0xc50 fs/inode.c:1947
__dentry_kill+0x209/0x660 fs/dcache.c:669
shrink_kill+0xa9/0x2c0 fs/dcache.c:1114
shrink_dentry_list+0x2e0/0x5e0 fs/dcache.c:1141
prune_dcache_sb+0x10e/0x180 fs/dcache.c:1222
super_cache_scan+0x369/0x4b0 fs/super.c:222
do_shrink_slab+0x6ec/0x1110 mm/shrinker.c:437
shrink_slab_memcg mm/shrinker.c:550 [inline]
shrink_slab+0x7ef/0x10d0 mm/shrinker.c:628
shrink_one+0x28a/0x7c0 mm/vmscan.c:4955
shrink_many mm/vmscan.c:5016 [inline]
lru_gen_shrink_node mm/vmscan.c:5094 [inline]
shrink_node+0x315d/0x3780 mm/vmscan.c:6081
kswapd_shrink_node mm/vmscan.c:6941 [inline]
balance_pgdat mm/vmscan.c:7124 [inline]
kswapd+0x147c/0x2800 mm/vmscan.c:7389
kthread+0x711/0x8a0 kernel/kthread.c:463
ret_from_fork+0x4bc/0x870 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

other info that might help us debug this:

Chain exists of:
sb_internal#2 --> &ip->i_rw_mutex --> fs_reclaim

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(fs_reclaim);
lock(&ip->i_rw_mutex);
lock(fs_reclaim);
rlock(sb_internal#2);

*** DEADLOCK ***

2 locks held by kswapd0/78:
#0: ffffffff8e247a40 (fs_reclaim){+.+.}-{0:0}, at: balance_pgdat mm/vmscan.c:7015 [inline]
#0: ffffffff8e247a40 (fs_reclaim){+.+.}-{0:0}, at: kswapd+0x951/0x2800 mm/vmscan.c:7389
#1: ffff8880332bc0e0 (&type->s_umount_key#50){.+.+}-{4:4}, at: super_trylock_shared fs/super.c:562 [inline]
#1: ffff8880332bc0e0 (&type->s_umount_key#50){.+.+}-{4:4}, at: super_cache_scan+0x91/0x4b0 fs/super.c:197

stack backtrace:
CPU: 0 UID: 0 PID: 78 Comm: kswapd0 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
Call Trace:
<TASK>
dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
print_circular_bug+0x2ee/0x310 kernel/locking/lockdep.c:2043
check_noncircular+0x134/0x160 kernel/locking/lockdep.c:2175
check_prev_add kernel/locking/lockdep.c:3165 [inline]
check_prevs_add kernel/locking/lockdep.c:3284 [inline]
validate_chain+0xb9b/0x2140 kernel/locking/lockdep.c:3908
__lock_acquire+0xab9/0xd20 kernel/locking/lockdep.c:5237
lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868
percpu_down_read_internal include/linux/percpu-rwsem.h:53 [inline]
percpu_down_read_freezable include/linux/percpu-rwsem.h:83 [inline]
__sb_start_write include/linux/fs.h:1916 [inline]
sb_start_intwrite include/linux/fs.h:2099 [inline]
__gfs2_trans_begin+0x42a/0x890 fs/gfs2/trans.c:76
gfs2_trans_begin+0x6f/0xe0 fs/gfs2/trans.c:118
gfs2_dirty_inode+0x3cb/0x600 fs/gfs2/super.c:508
__mark_inode_dirty+0x2ec/0xe10 fs/fs-writeback.c:2566
mark_inode_dirty_sync include/linux/fs.h:2619 [inline]
iput+0x381/0xc50 fs/inode.c:1947
__dentry_kill+0x209/0x660 fs/dcache.c:669
shrink_kill+0xa9/0x2c0 fs/dcache.c:1114
shrink_dentry_list+0x2e0/0x5e0 fs/dcache.c:1141
prune_dcache_sb+0x10e/0x180 fs/dcache.c:1222
super_cache_scan+0x369/0x4b0 fs/super.c:222
do_shrink_slab+0x6ec/0x1110 mm/shrinker.c:437
shrink_slab_memcg mm/shrinker.c:550 [inline]
shrink_slab+0x7ef/0x10d0 mm/shrinker.c:628
shrink_one+0x28a/0x7c0 mm/vmscan.c:4955
shrink_many mm/vmscan.c:5016 [inline]
lru_gen_shrink_node mm/vmscan.c:5094 [inline]
shrink_node+0x315d/0x3780 mm/vmscan.c:6081
kswapd_shrink_node mm/vmscan.c:6941 [inline]
balance_pgdat mm/vmscan.c:7124 [inline]
kswapd+0x147c/0x2800 mm/vmscan.c:7389
kthread+0x711/0x8a0 kernel/kthread.c:463
ret_from_fork+0x4bc/0x870 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
</TASK>


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