Hi folks -
I hit this lockdep splat on 4.18.0 this morning (the + in the version is
due to btrfs patch; xfs is unmodified). In my experience lockdep splats
involving mount are false positive, but Eric suggested I drop it here
just the same.
-Jeff
======================================================
WARNING: possible circular locking dependency detected
4.18.0-vanilla+ #8 Not tainted
------------------------------------------------------
kswapd0/56 is trying to acquire lock:
000000002f3c47dc (sb_internal){.+.+}, at: xfs_trans_alloc+0x19d/0x250 [xfs]
but task is already holding lock:
00000000e0553233 (fs_reclaim){+.+.}, at: __fs_reclaim_acquire+0x5/0x40
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #1 (fs_reclaim){+.+.}:
lock_acquire+0xbd/0x220
__fs_reclaim_acquire+0x2c/0x40
kmem_cache_alloc+0x2b/0x320
kmem_zone_alloc+0x95/0x100 [xfs]
xfs_trans_alloc+0x6f/0x250 [xfs]
xlog_recover_process_intents+0x1f6/0x300 [xfs]
xlog_recover_finish+0x18/0xa0 [xfs]
xfs_log_mount_finish+0x6d/0x110 [xfs]
xfs_mountfs+0x6f0/0xa40 [xfs]
xfs_fs_fill_super+0x520/0x6e0 [xfs]
mount_bdev+0x187/0x1c0
mount_fs+0x3a/0x160
vfs_kern_mount+0x66/0x150
do_mount+0x1d9/0xcf0
ksys_mount+0x7e/0xd0
__x64_sys_mount+0x21/0x30
do_syscall_64+0x5d/0x1a0
entry_SYSCALL_64_after_hwframe+0x49/0xbe
-> #0 (sb_internal){.+.+}:
__lock_acquire+0x436/0x770
lock_acquire+0xbd/0x220
__sb_start_write+0x166/0x1d0
xfs_trans_alloc+0x19d/0x250 [xfs]
xfs_iomap_write_allocate+0x1d7/0x330 [xfs]
xfs_map_blocks+0x2d7/0x550 [xfs]
xfs_do_writepage+0x26b/0x7a0 [xfs]
xfs_vm_writepage+0x28/0x50 [xfs]
pageout.isra.51+0x1ca/0x450
shrink_page_list+0x811/0xe30
shrink_inactive_list+0x2e2/0x770
shrink_node_memcg+0x32d/0x750
shrink_node+0xc9/0x470
balance_pgdat+0x175/0x360
kswapd+0x181/0x5d0
kthread+0xf8/0x130
ret_from_fork+0x3a/0x50
other info that might help us debug this:
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock(fs_reclaim);
lock(sb_internal);
lock(fs_reclaim);
lock(sb_internal);
*** DEADLOCK ***
1 lock held by kswapd0/56:
#0: 00000000e0553233 (fs_reclaim){+.+.}, at: __fs_reclaim_acquire+0x5/0x40
stack backtrace:
CPU: 0 PID: 56 Comm: kswapd0 Kdump: loaded Not tainted 4.18.0-vanilla+ #8
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
1.0.0-prebuilt.qemu-project.org 04/01/2014
Call Trace:
dump_stack+0x78/0xb3
print_circular_bug.isra.37+0x1f3/0x200
check_prev_add.constprop.46+0x717/0x730
validate_chain.isra.41+0x652/0x980
__lock_acquire+0x436/0x770
lock_acquire+0xbd/0x220
? xfs_trans_alloc+0x19d/0x250 [xfs]
__sb_start_write+0x166/0x1d0
? xfs_trans_alloc+0x19d/0x250 [xfs]
xfs_trans_alloc+0x19d/0x250 [xfs]
xfs_iomap_write_allocate+0x1d7/0x330 [xfs]
? xfs_iext_lookup_extent+0x11f/0x140 [xfs]
? xfs_iunlock+0x132/0x2f0 [xfs]
? xfs_map_blocks+0x100/0x550 [xfs]
xfs_map_blocks+0x2d7/0x550 [xfs]
xfs_do_writepage+0x26b/0x7a0 [xfs]
xfs_vm_writepage+0x28/0x50 [xfs]
pageout.isra.51+0x1ca/0x450
shrink_page_list+0x811/0xe30
shrink_inactive_list+0x2e2/0x770
shrink_node_memcg+0x32d/0x750
shrink_node+0xc9/0x470
balance_pgdat+0x175/0x360
kswapd+0x181/0x5d0
? wait_woken+0x80/0x80
kthread+0xf8/0x130
? balance_pgdat+0x360/0x360
? kthread_delayed_work_timer_fn+0x80/0x80
ret_from_fork+0x3a/0x50
--
Jeff Mahoney
SUSE Labs
