BTRFS info (device loop3): setting compat-ro feature flag for FREE_SPACE_TREE (0x1)
BTRFS info (device loop3): setting compat-ro feature flag for FREE_SPACE_TREE_VALID (0x2)
======================================================
WARNING: possible circular locking dependency detected
5.15.181-syzkaller #0 Not tainted
------------------------------------------------------
syz.3.18/5076 is trying to acquire lock:
ffff0000ebc44650 (sb_internal#2){.+.+}-{0:0}, at: btrfs_join_transaction+0x30/0x40 fs/btrfs/transaction.c:793

but task is already holding lock:
ffff0000d9899818 (&mm->mmap_lock){++++}-{3:3}, at: mmap_write_lock_killable include/linux/mmap_lock.h:87 [inline]
ffff0000d9899818 (&mm->mmap_lock){++++}-{3:3}, at: vm_mmap_pgoff+0x138/0x284 mm/util.c:549

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #4 (&mm->mmap_lock){++++}-{3:3}:
       __might_fault+0xc8/0x128 mm/memory.c:5357
       filldir64+0x2bc/0x9e4 fs/readdir.c:335
       dir_emit_dot include/linux/fs.h:3717 [inline]
       dir_emit_dots include/linux/fs.h:3728 [inline]
       dcache_readdir+0x140/0x65c fs/libfs.c:196
       iterate_dir+0x1f0/0x4cc fs/readdir.c:-1
       __do_sys_getdents64 fs/readdir.c:369 [inline]
       __se_sys_getdents64 fs/readdir.c:354 [inline]
       __arm64_sys_getdents64+0x11c/0x340 fs/readdir.c:354
       __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
       invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:52
       el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142
       do_el0_svc+0x58/0x14c arch/arm64/kernel/syscall.c:181
       el0_svc+0x78/0x1e0 arch/arm64/kernel/entry-common.c:608
       el0t_64_sync_handler+0xcc/0xe4 arch/arm64/kernel/entry-common.c:626
       el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584

-> #3 (&type->i_mutex_dir_key#5){++++}-{3:3}:
       down_read+0xc0/0x390 kernel/locking/rwsem.c:1498
       inode_lock_shared include/linux/fs.h:797 [inline]
       lookup_slow+0x4c/0x80 fs/namei.c:1679
       walk_component+0x2b0/0x3a8 fs/namei.c:1976
       lookup_last fs/namei.c:2431 [inline]
       path_lookupat+0x13c/0x3d0 fs/namei.c:2455
       filename_lookup+0x180/0x414 fs/namei.c:2484
       kern_path+0x4c/0x190 fs/namei.c:2582
       lookup_bdev+0xbc/0x244 block/bdev.c:982
       device_matched fs/btrfs/volumes.c:568 [inline]
       btrfs_free_stale_devices+0x614/0x908 fs/btrfs/volumes.c:608
       btrfs_forget_devices+0x5c/0x98 fs/btrfs/volumes.c:1431
       btrfs_control_ioctl+0x130/0x248 fs/btrfs/super.c:2450
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:874 [inline]
       __se_sys_ioctl fs/ioctl.c:860 [inline]
       __arm64_sys_ioctl+0x14c/0x1c8 fs/ioctl.c:860
       __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
       invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:52
       el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142
       do_el0_svc+0x58/0x14c arch/arm64/kernel/syscall.c:181
       el0_svc+0x78/0x1e0 arch/arm64/kernel/entry-common.c:608
       el0t_64_sync_handler+0xcc/0xe4 arch/arm64/kernel/entry-common.c:626
       el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584

-> #2 (&fs_devs->device_list_mutex){+.+.}-{3:3}:
       __mutex_lock_common+0x194/0x1edc kernel/locking/mutex.c:596
       __mutex_lock kernel/locking/mutex.c:729 [inline]
       mutex_lock_nested+0xac/0x11c kernel/locking/mutex.c:743
       btrfs_run_dev_stats+0xe0/0xcac fs/btrfs/volumes.c:7985
       commit_cowonly_roots+0x144/0x7e8 fs/btrfs/transaction.c:1292
       btrfs_commit_transaction+0xf04/0x3044 fs/btrfs/transaction.c:2394
       btrfs_clear_free_space_tree+0x5cc/0x9cc fs/btrfs/free-space-tree.c:1264
       btrfs_start_pre_rw_mount+0x240/0x568 fs/btrfs/disk-io.c:3079
       open_ctree+0x1ef0/0x27b8 fs/btrfs/disk-io.c:3634
       btrfs_fill_super+0x1b4/0x2d4 fs/btrfs/super.c:1387
       btrfs_mount_root+0x730/0x780 fs/btrfs/super.c:1751
       legacy_get_tree+0xd4/0x16c fs/fs_context.c:611
       vfs_get_tree+0x90/0x274 fs/super.c:1530
       fc_mount fs/namespace.c:1000 [inline]
       vfs_kern_mount+0xdc/0x178 fs/namespace.c:1030
       btrfs_mount+0x2a0/0x8d4 fs/btrfs/super.c:1811
       legacy_get_tree+0xd4/0x16c fs/fs_context.c:611
       vfs_get_tree+0x90/0x274 fs/super.c:1530
       do_new_mount+0x228/0x810 fs/namespace.c:3013
       path_mount+0x5b4/0x1000 fs/namespace.c:3343
       do_mount fs/namespace.c:3356 [inline]
       __do_sys_mount fs/namespace.c:3564 [inline]
       __se_sys_mount fs/namespace.c:3541 [inline]
       __arm64_sys_mount+0x514/0x5e4 fs/namespace.c:3541
       __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
       invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:52
       el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142
       do_el0_svc+0x58/0x14c arch/arm64/kernel/syscall.c:181
       el0_svc+0x78/0x1e0 arch/arm64/kernel/entry-common.c:608
       el0t_64_sync_handler+0xcc/0xe4 arch/arm64/kernel/entry-common.c:626
       el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584

-> #1 (&fs_info->tree_log_mutex){+.+.}-{3:3}:
       __lock_release kernel/locking/lockdep.c:5339 [inline]
       lock_release+0x2e8/0x8e8 kernel/locking/lockdep.c:5643
       __mutex_unlock_slowpath+0xc0/0x5d8 kernel/locking/mutex.c:851
       mutex_unlock+0x90/0xec kernel/locking/mutex.c:536
       btrfs_commit_transaction+0x1630/0x3044 fs/btrfs/transaction.c:2441
       btrfs_clear_free_space_tree+0x5cc/0x9cc fs/btrfs/free-space-tree.c:1264
       btrfs_start_pre_rw_mount+0x240/0x568 fs/btrfs/disk-io.c:3079
       open_ctree+0x1ef0/0x27b8 fs/btrfs/disk-io.c:3634
       btrfs_fill_super+0x1b4/0x2d4 fs/btrfs/super.c:1387
       btrfs_mount_root+0x730/0x780 fs/btrfs/super.c:1751
       legacy_get_tree+0xd4/0x16c fs/fs_context.c:611
       vfs_get_tree+0x90/0x274 fs/super.c:1530
       fc_mount fs/namespace.c:1000 [inline]
       vfs_kern_mount+0xdc/0x178 fs/namespace.c:1030
       btrfs_mount+0x2a0/0x8d4 fs/btrfs/super.c:1811
       legacy_get_tree+0xd4/0x16c fs/fs_context.c:611
       vfs_get_tree+0x90/0x274 fs/super.c:1530
       do_new_mount+0x228/0x810 fs/namespace.c:3013
       path_mount+0x5b4/0x1000 fs/namespace.c:3343
       do_mount fs/namespace.c:3356 [inline]
       __do_sys_mount fs/namespace.c:3564 [inline]
       __se_sys_mount fs/namespace.c:3541 [inline]
       __arm64_sys_mount+0x514/0x5e4 fs/namespace.c:3541
       __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
       invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:52
       el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142
       do_el0_svc+0x58/0x14c arch/arm64/kernel/syscall.c:181
       el0_svc+0x78/0x1e0 arch/arm64/kernel/entry-common.c:608
       el0t_64_sync_handler+0xcc/0xe4 arch/arm64/kernel/entry-common.c:626
       el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584

-> #0 (sb_internal#2){.+.+}-{0:0}:
       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+0x2928/0x651c kernel/locking/lockdep.c:5012
       lock_acquire+0x1f4/0x620 kernel/locking/lockdep.c:5623
       percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
       __sb_start_write include/linux/fs.h:1811 [inline]
       sb_start_intwrite include/linux/fs.h:1928 [inline]
       start_transaction+0x624/0x13f0 fs/btrfs/transaction.c:680
       btrfs_join_transaction+0x30/0x40 fs/btrfs/transaction.c:793
       btrfs_dirty_inode+0xb4/0x1c0 fs/btrfs/inode.c:6436
       btrfs_update_time+0x224/0x248 fs/btrfs/inode.c:6478
       inode_update_time fs/inode.c:1893 [inline]
       touch_atime+0x3d0/0x914 fs/inode.c:1966
       file_accessed include/linux/fs.h:2521 [inline]
       btrfs_file_mmap+0xb0/0x11c fs/btrfs/file.c:2449
       call_mmap include/linux/fs.h:2177 [inline]
       mmap_file+0x6c/0xc8 mm/util.c:1092
       __mmap_region mm/mmap.c:1784 [inline]
       mmap_region+0xadc/0x1390 mm/mmap.c:2921
       do_mmap+0x67c/0xdb4 mm/mmap.c:1574
       vm_mmap_pgoff+0x184/0x284 mm/util.c:551
       ksys_mmap_pgoff+0x410/0x620 mm/mmap.c:1623
       __do_sys_mmap arch/arm64/kernel/sys.c:28 [inline]
       __se_sys_mmap arch/arm64/kernel/sys.c:21 [inline]
       __arm64_sys_mmap+0xf8/0x110 arch/arm64/kernel/sys.c:21
       __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
       invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:52
       el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142
       do_el0_svc+0x58/0x14c arch/arm64/kernel/syscall.c:181
       el0_svc+0x78/0x1e0 arch/arm64/kernel/entry-common.c:608
       el0t_64_sync_handler+0xcc/0xe4 arch/arm64/kernel/entry-common.c:626
       el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584

other info that might help us debug this:

Chain exists of:
  sb_internal#2 --> &type->i_mutex_dir_key#5 --> &mm->mmap_lock

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&mm->mmap_lock);
                               lock(&type->i_mutex_dir_key#5);
                               lock(&mm->mmap_lock);
  lock(sb_internal#2);

 *** DEADLOCK ***

2 locks held by syz.3.18/5076:
 #0: ffff0000d9899818 (&mm->mmap_lock){++++}-{3:3}, at: mmap_write_lock_killable include/linux/mmap_lock.h:87 [inline]
 #0: ffff0000d9899818 (&mm->mmap_lock){++++}-{3:3}, at: vm_mmap_pgoff+0x138/0x284 mm/util.c:549
 #1: ffff0000ebc44460 (sb_writers#12){.+.+}-{0:0}, at: file_accessed include/linux/fs.h:2521 [inline]
 #1: ffff0000ebc44460 (sb_writers#12){.+.+}-{0:0}, at: btrfs_file_mmap+0xb0/0x11c fs/btrfs/file.c:2449

stack backtrace:
CPU: 1 PID: 5076 Comm: syz.3.18 Not tainted 5.15.181-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/19/2025
Call trace:
 dump_backtrace+0x0/0x43c arch/arm64/kernel/stacktrace.c:152
 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:216
 __dump_stack+0x30/0x40 lib/dump_stack.c:88
 dump_stack_lvl+0xf8/0x160 lib/dump_stack.c:106
 dump_stack+0x1c/0x5c lib/dump_stack.c:113
 print_circular_bug+0x148/0x1b0 kernel/locking/lockdep.c:2011
 check_noncircular+0x240/0x2d4 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+0x2928/0x651c kernel/locking/lockdep.c:5012
 lock_acquire+0x1f4/0x620 kernel/locking/lockdep.c:5623
 percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
 __sb_start_write include/linux/fs.h:1811 [inline]
 sb_start_intwrite include/linux/fs.h:1928 [inline]
 start_transaction+0x624/0x13f0 fs/btrfs/transaction.c:680
 btrfs_join_transaction+0x30/0x40 fs/btrfs/transaction.c:793
 btrfs_dirty_inode+0xb4/0x1c0 fs/btrfs/inode.c:6436
 btrfs_update_time+0x224/0x248 fs/btrfs/inode.c:6478
 inode_update_time fs/inode.c:1893 [inline]
 touch_atime+0x3d0/0x914 fs/inode.c:1966
 file_accessed include/linux/fs.h:2521 [inline]
 btrfs_file_mmap+0xb0/0x11c fs/btrfs/file.c:2449
 call_mmap include/linux/fs.h:2177 [inline]
 mmap_file+0x6c/0xc8 mm/util.c:1092
 __mmap_region mm/mmap.c:1784 [inline]
 mmap_region+0xadc/0x1390 mm/mmap.c:2921
 do_mmap+0x67c/0xdb4 mm/mmap.c:1574
 vm_mmap_pgoff+0x184/0x284 mm/util.c:551
 ksys_mmap_pgoff+0x410/0x620 mm/mmap.c:1623
 __do_sys_mmap arch/arm64/kernel/sys.c:28 [inline]
 __se_sys_mmap arch/arm64/kernel/sys.c:21 [inline]
 __arm64_sys_mmap+0xf8/0x110 arch/arm64/kernel/sys.c:21
 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
 invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:52
 el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142
 do_el0_svc+0x58/0x14c arch/arm64/kernel/syscall.c:181
 el0_svc+0x78/0x1e0 arch/arm64/kernel/entry-common.c:608
 el0t_64_sync_handler+0xcc/0xe4 arch/arm64/kernel/entry-common.c:626
 el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584