possible deadlock in nilfs_bmap_lookup_at_level

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 3f8a27f9e27b Linux 4.19.211
git tree: linux-4.19.y
console output: https://syzkaller.appspot.com/x/log.txt?x=121257d6880000
kernel config: https://syzkaller.appspot.com/x/.config?x=9b9277b418617afe
dashboard link: https://syzkaller.appspot.com/bug?extid=34b9365911d60f079def
compiler: gcc version 10.2.1 20210110 (Debian 10.2.1-6)

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/98c0bdb4abb3/disk-3f8a27f9.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/ea228ff02669/vmlinux-3f8a27f9.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+34b936...@syzkaller.appspotmail.com

NILFS (loop5): segctord starting. Construction interval = 5 seconds, CP frequency < 30 seconds
============================================
WARNING: possible recursive locking detected
4.19.211-syzkaller #0 Not tainted
--------------------------------------------
syz-executor.5/22112 is trying to acquire lock:
00000000e41de388 (&nilfs_bmap_dat_lock_key){++++}, at: nilfs_bmap_lookup_at_level+0x7b/0x3e0 fs/nilfs2/bmap.c:68

but task is already holding lock:
00000000a9805b5c (&nilfs_bmap_dat_lock_key){++++}, at: nilfs_bmap_lookup_at_level+0x7b/0x3e0 fs/nilfs2/bmap.c:68

other info that might help us debug this:
Possible unsafe locking scenario:

CPU0
----
lock(&nilfs_bmap_dat_lock_key);
lock(&nilfs_bmap_dat_lock_key);

*** DEADLOCK ***

May be due to missing lock nesting notation

3 locks held by syz-executor.5/22112:
#0: 00000000339a801c (&type->s_umount_key#97/1){+.+.}, at: alloc_super fs/super.c:226 [inline]
#0: 00000000339a801c (&type->s_umount_key#97/1){+.+.}, at: sget_userns+0x20b/0xcd0 fs/super.c:519
#1: 00000000cadce1ff (&dat_lock_key){.+.+}, at: __nilfs_read_inode fs/nilfs2/inode.c:482 [inline]
#1: 00000000cadce1ff (&dat_lock_key){.+.+}, at: nilfs_iget+0x1cf/0x860 fs/nilfs2/inode.c:592
#2: 00000000a9805b5c (&nilfs_bmap_dat_lock_key){++++}, at: nilfs_bmap_lookup_at_level+0x7b/0x3e0 fs/nilfs2/bmap.c:68

stack backtrace:
CPU: 1 PID: 22112 Comm: syz-executor.5 Not tainted 4.19.211-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/22/2022
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x1fc/0x2ef lib/dump_stack.c:118
print_deadlock_bug kernel/locking/lockdep.c:1764 [inline]
check_deadlock kernel/locking/lockdep.c:1808 [inline]
validate_chain kernel/locking/lockdep.c:2404 [inline]
__lock_acquire.cold+0x121/0x57e kernel/locking/lockdep.c:3416
lock_acquire+0x170/0x3c0 kernel/locking/lockdep.c:3908
down_read+0x36/0x80 kernel/locking/rwsem.c:24
nilfs_bmap_lookup_at_level+0x7b/0x3e0 fs/nilfs2/bmap.c:68
nilfs_bmap_lookup fs/nilfs2/bmap.h:170 [inline]
nilfs_mdt_submit_block.constprop.0+0x1a5/0xaa0 fs/nilfs2/mdt.c:142
nilfs_mdt_read_block+0x96/0x3e0 fs/nilfs2/mdt.c:175
nilfs_mdt_get_block+0xe6/0xd40 fs/nilfs2/mdt.c:250
nilfs_palloc_get_block+0xc4/0x2b0 fs/nilfs2/alloc.c:216
nilfs_palloc_get_entry_block+0x17b/0x230 fs/nilfs2/alloc.c:318
nilfs_dat_translate+0x7e/0x480 fs/nilfs2/dat.c:391
nilfs_btnode_submit_block+0x217/0x830 fs/nilfs2/btnode.c:80
__nilfs_btree_get_block+0xca/0x680 fs/nilfs2/btree.c:478
nilfs_btree_do_lookup+0x3eb/0x7c0 fs/nilfs2/btree.c:567
nilfs_btree_lookup+0x47/0x110 fs/nilfs2/btree.c:684
nilfs_bmap_lookup_at_level+0xcd/0x3e0 fs/nilfs2/bmap.c:69
nilfs_bmap_lookup fs/nilfs2/bmap.h:170 [inline]
nilfs_mdt_submit_block.constprop.0+0x1a5/0xaa0 fs/nilfs2/mdt.c:142
nilfs_mdt_read_block+0x96/0x3e0 fs/nilfs2/mdt.c:175
nilfs_mdt_get_block+0xe6/0xd40 fs/nilfs2/mdt.c:250
nilfs_palloc_get_block+0xc4/0x2b0 fs/nilfs2/alloc.c:216
nilfs_palloc_get_entry_block+0x17b/0x230 fs/nilfs2/alloc.c:318
nilfs_ifile_get_inode_block+0xbf/0x170 fs/nilfs2/ifile.c:143
__nilfs_read_inode fs/nilfs2/inode.c:483 [inline]
nilfs_iget+0x204/0x860 fs/nilfs2/inode.c:592
nilfs_get_root_dentry+0x26/0x250 fs/nilfs2/super.c:908
nilfs_fill_super fs/nilfs2/super.c:1082 [inline]
nilfs_mount+0xac8/0xe70 fs/nilfs2/super.c:1321
mount_fs+0xa3/0x310 fs/super.c:1261
vfs_kern_mount.part.0+0x68/0x470 fs/namespace.c:961
vfs_kern_mount fs/namespace.c:951 [inline]
do_new_mount fs/namespace.c:2492 [inline]
do_mount+0x115c/0x2f50 fs/namespace.c:2822
ksys_mount+0xcf/0x130 fs/namespace.c:3038
__do_sys_mount fs/namespace.c:3052 [inline]
__se_sys_mount fs/namespace.c:3049 [inline]
__x64_sys_mount+0xba/0x150 fs/namespace.c:3049
do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x7fe665755ada
Code: 48 c7 c2 b8 ff ff ff f7 d8 64 89 02 b8 ff ff ff ff eb d2 e8 b8 04 00 00 0f 1f 84 00 00 00 00 00 49 89 ca b8 a5 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fe6640c6f88 EFLAGS: 00000202 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 0000000020000200 RCX: 00007fe665755ada
RDX: 00000000200000c0 RSI: 0000000020000100 RDI: 00007fe6640c6fe0
RBP: 00007fe6640c7020 R08: 00007fe6640c7020 R09: 00000000200000c0
R10: 0000000000000000 R11: 0000000000000202 R12: 00000000200000c0
R13: 0000000020000100 R14: 00007fe6640c6fe0 R15: 00000000200007c0
NILFS (loop5): error -2 reading inode: ino=2
NILFS (loop5): error -2 getting root inode
NILFS (loop3): segctord starting. Construction interval = 5 seconds, CP frequency < 30 seconds
NILFS (loop3): segctord starting. Construction interval = 5 seconds, CP frequency < 30 seconds
NILFS (loop5): segctord starting. Construction interval = 5 seconds, CP frequency < 30 seconds
NILFS (loop3): segctord starting. Construction interval = 5 seconds, CP frequency < 30 seconds
NILFS (loop5): segctord starting. Construction interval = 5 seconds, CP frequency < 30 seconds
NILFS (loop5): broken superblock, retrying with spare superblock (blocksize = 1024)
NILFS (loop5): mounting unchecked fs
NILFS (loop5): invalid segment: Checksum error in segment payload
NILFS (loop5): unable to fall back to spare super block
NILFS (loop5): error -22 while searching super root
NILFS (loop5): broken superblock, retrying with spare superblock (blocksize = 1024)
NILFS (loop5): mounting unchecked fs
NILFS (loop5): invalid segment: Checksum error in segment payload
NILFS (loop5): unable to fall back to spare super block
NILFS (loop5): error -22 while searching super root
NILFS (loop5): broken superblock, retrying with spare superblock (blocksize = 1024)
NILFS (loop5): mounting unchecked fs
NILFS (loop5): invalid segment: Checksum error in segment payload
NILFS (loop5): unable to fall back to spare super block
NILFS (loop5): error -22 while searching super root
attempt to access beyond end of device
loop2: rw=2049, want=160, limit=127
attempt to access beyond end of device
loop2: rw=1, want=152, limit=127
attempt to access beyond end of device
loop2: rw=2049, want=160, limit=127
attempt to access beyond end of device
loop2: rw=1, want=152, limit=127
NILFS error (device loop5): nilfs_check_page: bad entry in directory #2: rec_len is smaller than minimal - offset=16, inode=792633534417207298, rec_len=0, name_len=0
NILFS (loop5): segctord starting. Construction interval = 5 seconds, CP frequency < 30 seconds
Remounting filesystem read-only
NILFS (loop5): segctord starting. Construction interval = 5 seconds, CP frequency < 30 seconds
NILFS error (device loop5): nilfs_check_page: bad entry in directory #2: rec_len is smaller than minimal - offset=16, inode=792633534417207298, rec_len=0, name_len=0
NILFS (loop5): segctord starting. Construction interval = 5 seconds, CP frequency < 30 seconds
Remounting filesystem read-only
NILFS (loop3): segctord starting. Construction interval = 5 seconds, CP frequency < 30 seconds
NILFS (loop5): invalid segment: Checksum error in segment payload
NILFS (loop5): trying rollback from an earlier position
NILFS (loop5): invalid segment: Checksum error in segment payload
NILFS (loop5): error -22 while searching super root
NILFS (loop3): segctord starting. Construction interval = 5 seconds, CP frequency < 30 seconds
NILFS (loop5): invalid segment: Checksum error in segment payload
NILFS (loop5): trying rollback from an earlier position
NILFS (loop5): invalid segment: Checksum error in segment payload
NILFS (loop5): error -22 while searching super root
NILFS (loop3): segctord starting. Construction interval = 5 seconds, CP frequency < 30 seconds
NILFS (loop5): invalid segment: Checksum error in segment payload
NILFS (loop5): trying rollback from an earlier position
NILFS (loop5): invalid segment: Checksum error in segment payload
NILFS (loop5): error -22 while searching super root
NILFS (loop3): segctord starting. Construction interval = 5 seconds, CP frequency < 30 seconds
NILFS (loop3): segctord starting. Construction interval = 5 seconds, CP frequency < 30 seconds
NILFS (loop5): segctord starting. Construction interval = 5 seconds, CP frequency < 30 seconds
NILFS (loop3): segctord starting. Construction interval = 5 seconds, CP frequency < 30 seconds
NILFS (loop5): segctord starting. Construction interval = 5 seconds, CP frequency < 30 seconds
NILFS error (device loop5): nilfs_check_page: bad entry in directory #2: rec_len is smaller than minimal - offset=16, inode=792633534417207298, rec_len=0, name_len=0
NILFS (loop3): segctord starting. Construction interval = 5 seconds, CP frequency < 30 seconds
Remounting filesystem read-only
NILFS (loop3): segctord starting. Construction interval = 5 seconds, CP frequency < 30 seconds
NILFS (loop5): broken superblock, retrying with spare superblock (blocksize = 1024)
NILFS (loop5): segctord starting. Construction interval = 5 seconds, CP frequency < 30 seconds
NILFS (loop3): segctord starting. Construction interval = 5 seconds, CP frequency < 30 seconds
attempt to access beyond end of device
loop2: rw=1, want=144, limit=127
NILFS (loop5): broken superblock, retrying with spare superblock (blocksize = 1024)
NILFS (loop5): segctord starting. Construction interval = 5 seconds, CP frequency < 30 seconds
NILFS (loop3): segctord starting. Construction interval = 5 seconds, CP frequency < 30 seconds
attempt to access beyond end of device
loop2: rw=1, want=144, limit=127
NILFS (loop5): broken superblock, retrying with spare superblock (blocksize = 1024)
NILFS (loop3): segctord starting. Construction interval = 5 seconds, CP frequency < 30 seconds
NILFS (loop5): segctord starting. Construction interval = 5 seconds, CP frequency < 30 seconds
attempt to access beyond end of device
loop2: rw=1, want=144, limit=127
NILFS (loop3): segctord starting. Construction interval = 5 seconds, CP frequency < 30 seconds
NILFS (loop5): segctord starting. Construction interval = 5 seconds, CP frequency < 30 seconds
NILFS (loop3): segctord starting. Construction interval = 5 seconds, CP frequency < 30 seconds
attempt to access beyond end of device
loop2: rw=1, want=144, limit=127
netlink: 24 bytes leftover after parsing attributes in process `syz-executor.0'.
NILFS (loop5): segctord starting. Construction interval = 5 seconds, CP frequency < 30 seconds
NILFS (loop3): segctord starting. Construction interval = 5 seconds, CP frequency < 30 seconds
netlink: 24 bytes leftover after parsing attributes in process `syz-executor.0'.
netlink: 24 bytes leftover after parsing attributes in process `syz-executor.0'.
NILFS (loop5): segctord starting. Construction interval = 5 seconds, CP frequency < 30 seconds
netlink: 24 bytes leftover after parsing attributes in process `syz-executor.0'.
NILFS (loop3): segctord starting. Construction interval = 5 seconds, CP frequency < 30 seconds
netlink: 24 bytes leftover after parsing attributes in process `syz-executor.0'.
NILFS (loop5): segctord starting. Construction interval = 5 seconds, CP frequency < 30 seconds
NILFS error (device loop5): nilfs_check_page: bad entry in directory #2: rec_len is smaller than minimal - offset=16, inode=792633534417207298, rec_len=0, name_len=0
attempt to access beyond end of device
loop2: rw=1, want=144, limit=127
Remounting filesystem read-only
NILFS (loop3): segctord starting. Construction interval = 5 seconds, CP frequency < 30 seconds
attempt to access beyond end of device
loop2: rw=1, want=144, limit=127
NILFS (loop5): segctord starting. Construction interval = 5 seconds, CP frequency < 30 seconds
NILFS (loop3): segctord starting. Construction interval = 5 seconds, CP frequency < 30 seconds
NILFS (loop3): segctord starting. Construction interval = 5 seconds, CP frequency < 30 seconds
attempt to access beyond end of device
loop2: rw=1, want=144, limit=127
NILFS (loop5): segctord starting. Construction interval = 5 seconds, CP frequency < 30 seconds
attempt to access beyond end of device
loop2: rw=1, want=144, limit=127
NILFS (loop3): segctord starting. Construction interval = 5 seconds, CP frequency < 30 seconds
netlink: 24 bytes leftover after parsing attributes in process `syz-executor.0'.
NILFS (loop5): segctord starting. Construction interval = 5 seconds, CP frequency < 30 seconds
netlink: 24 bytes leftover after parsing attributes in process `syz-executor.3'.
attempt to access beyond end of device
loop2: rw=1, want=144, limit=127
netlink: 24 bytes leftover after parsing attributes in process `syz-executor.0'.
NILFS (loop5): segctord starting. Construction interval = 5 seconds, CP frequency < 30 seconds
NILFS (loop3): segctord starting. Construction interval = 5 seconds, CP frequency < 30 seconds
netlink: 24 bytes leftover after parsing attributes in process `syz-executor.3'.
attempt to access beyond end of device
loop2: rw=1, want=144, limit=127
netlink: 24 bytes leftover after parsing attributes in process `syz-executor.0'.
NILFS error (device loop3): nilfs_check_page: bad entry in directory #2: rec_len is smaller than minimal - offset=16, inode=792633534417207298, rec_len=0, name_len=0
NILFS (loop5): segctord starting. Construction interval = 5 seconds, CP frequency < 30 seconds
Remounting filesystem read-only
attempt to access beyond end of device
loop2: rw=1, want=144, limit=127
NILFS (loop5): invalid segment: Checksum error in segment payload
NILFS (loop5): trying rollback from an earlier position
NILFS (loop5): invalid segment: Checksum error in segment payload
NILFS (loop3): segctord starting. Construction interval = 5 seconds, CP frequency < 30 seconds
NILFS (loop5): error -22 while searching super root


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.