Hi Darrick,
Thanks for your reflink work for xfs first, that's quite a good and
useful feature, also helps to debug btrfs problems.
(Without that, there is no good reference for reflink behavior)
But when testing your for-dave-for-4.6 branch, even I'm just testing
btrfs with xfstests, kernel report some strange lockdep from xfs:
------
run fstests generic/175 at 2016-05-12 13:22:06
BTRFS: device fsid 3d5c9c3b-2d08-4f0b-9663-00a88cd218da devid 1 transid
3 /dev/sdb6
BTRFS info (device sdb6): disk space caching is enabled
BTRFS: has skinny extents
BTRFS: flagging fs with big metadata feature
BTRFS: creating UUID tree
BTRFS: device fsid bb75eb48-4c5f-4b75-a41d-f642d70c7294 devid 1 transid
3 /dev/sdb6
BTRFS info (device sdb6): disk space caching is enabled
BTRFS: has skinny extents
BTRFS: flagging fs with big metadata feature
BTRFS: creating UUID tree
=================================
[ INFO: inconsistent lock state ]
4.5.0-rc2+ #4 Tainted: G O
---------------------------------
inconsistent {RECLAIM_FS-ON-R} -> {IN-RECLAIM_FS-W} usage.
kswapd0/543 [HC0[0]:SC0[0]:HE1:SE1] takes:
(&xfs_nondir_ilock_class){++++-+}, at: [<ffffffffa00781f7>]
xfs_ilock+0x177/0x200 [xfs]
{RECLAIM_FS-ON-R} state was registered at:
[<ffffffff8110f369>] mark_held_locks+0x79/0xa0
[<ffffffff81113a43>] lockdep_trace_alloc+0xb3/0x100
[<ffffffff81224623>] kmem_cache_alloc+0x33/0x230
[<ffffffffa008acc1>] kmem_zone_alloc+0x81/0x120 [xfs]
[<ffffffffa005456e>] xfs_refcountbt_init_cursor+0x3e/0xa0 [xfs]
[<ffffffffa0053455>] __xfs_refcount_find_shared+0x75/0x580 [xfs]
[<ffffffffa00539e4>] xfs_refcount_find_shared+0x84/0xb0 [xfs]
[<ffffffffa005dcb8>] xfs_getbmap+0x608/0x8c0 [xfs]
[<ffffffffa007634b>] xfs_vn_fiemap+0xab/0xc0 [xfs]
[<ffffffff81244208>] do_vfs_ioctl+0x498/0x670
[<ffffffff81244459>] SyS_ioctl+0x79/0x90
[<ffffffff81847cd7>] entry_SYSCALL_64_fastpath+0x12/0x6f
irq event stamp: 510775
hardirqs last enabled at (510775): [<ffffffff812245d0>]
__slab_alloc+0x50/0x70
hardirqs last disabled at (510774): [<ffffffff812245ae>]
__slab_alloc+0x2e/0x70
softirqs last enabled at (510506): [<ffffffff810c8ea8>]
__do_softirq+0x358/0x430
softirqs last disabled at (510489): [<ffffffff810c911d>] irq_exit+0xad/0xb0
other info that might help us debug this:
Possible unsafe locking scenario:
CPU0
----
lock(&xfs_nondir_ilock_class);
<Interrupt>
lock(&xfs_nondir_ilock_class);
*** DEADLOCK ***
3 locks held by kswapd0/543:
#0: (shrinker_rwsem){++++..}, at: [<ffffffff811e0b78>]
shrink_slab.part.63.constprop.79+0x48/0x4e0
#1: (&type->s_umount_key#26){++++++}, at: [<ffffffff81232ffb>]
trylock_super+0x1b/0x50
#2: (sb_internal){.+.+.?}, at: [<ffffffff812327f4>]
__sb_start_write+0xb4/0xf0
stack backtrace:
CPU: 0 PID: 543 Comm: kswapd0 Tainted: G O 4.5.0-rc2+ #4
Hardware name: innotek GmbH VirtualBox/VirtualBox, BIOS VirtualBox
12/01/2006
ffffffff82a34f10 ffff88003aa078d0 ffffffff813a14f9 ffff88003d8551c0
ffff88003aa07920 ffffffff8110ec65 0000000000000000 0000000000000001
ffff880000000001 000000000000000b 0000000000000008 ffff88003d855aa0
Call Trace:
[<ffffffff813a14f9>] dump_stack+0x4b/0x72
[<ffffffff8110ec65>] print_usage_bug+0x215/0x240
[<ffffffff8110ee85>] mark_lock+0x1f5/0x660
[<ffffffff8110e100>] ? print_shortest_lock_dependencies+0x1a0/0x1a0
[<ffffffff811102e0>] __lock_acquire+0xa80/0x1e50
[<ffffffff8122474e>] ? kmem_cache_alloc+0x15e/0x230
[<ffffffffa008acc1>] ? kmem_zone_alloc+0x81/0x120 [xfs]
[<ffffffff811122e8>] lock_acquire+0xd8/0x1e0
[<ffffffffa00781f7>] ? xfs_ilock+0x177/0x200 [xfs]
[<ffffffffa0083a70>] ? xfs_reflink_cancel_cow_range+0x150/0x300 [xfs]
[<ffffffff8110aace>] down_write_nested+0x5e/0xc0
[<ffffffffa00781f7>] ? xfs_ilock+0x177/0x200 [xfs]
[<ffffffffa00781f7>] xfs_ilock+0x177/0x200 [xfs]
[<ffffffffa0083a70>] xfs_reflink_cancel_cow_range+0x150/0x300 [xfs]
[<ffffffffa0085bdc>] xfs_fs_evict_inode+0xdc/0x1e0 [xfs]
[<ffffffff8124d7d5>] evict+0xc5/0x190
[<ffffffff8124d8d9>] dispose_list+0x39/0x60
[<ffffffff8124eb2b>] prune_icache_sb+0x4b/0x60
[<ffffffff8123317f>] super_cache_scan+0x14f/0x1a0
[<ffffffff811e0d19>] shrink_slab.part.63.constprop.79+0x1e9/0x4e0
[<ffffffff811e50ee>] shrink_zone+0x15e/0x170
[<ffffffff811e5ef1>] kswapd+0x4f1/0xa80
[<ffffffff811e5a00>] ? zone_reclaim+0x230/0x230
[<ffffffff810e6882>] kthread+0xf2/0x110
[<ffffffff810e6790>] ? kthread_create_on_node+0x220/0x220
[<ffffffff8184803f>] ret_from_fork+0x3f/0x70
[<ffffffff810e6790>] ? kthread_create_on_node+0x220/0x220
hrtimer: interrupt took 4824925 ns
BTRFS info (device sdb6): disk space caching is enabled
BTRFS: has skinny extents
------
The test machine is using normal xfs (without -m reflink=1) as its root.
As you can see, it's running generic/175 on *BTRFS*, not *XFS*, but
still lockdep warning from xfs.
Hopes the output could help you.
Thanks,
Qu
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