Hi all,
I have found a kernel warning of btrfs ,during run my shell script in
qemu qemu virtual machine.
Linux mainline version Linux 4.15-rc2 (ae64f9bd)
The script try to copy a big file(15G) into btrfs filesystem,when I
login virtual machine,then run the script,A kernel warning will be
triggered within about ten file copies.
=========================================================
#!/bin/sh
function btrfs_test()
{
umount /mnt/vdb
mkfs.btrfs -f /dev/vdb
mount -o compress=$1 /dev/vdb /mnt/vdb
cp ../data.tar /mnt/vdb
sleep 10
btrfs filesystem sync /mnt/vdb
}
function loop_test()
{
for k in $( seq 1 100 )
do
btrfs_test zstd
done
}
loop_test
==========================================================
Kernl Warning content:
[ 291.809047] ============================================
[ 291.809981] WARNING: possible recursive locking detected
[ 291.810913] 4.15.0-rc2-327.58.59.16.x86_64.debug+ #8 Not tainted
[ 291.811908] --------------------------------------------
[ 291.812792] khugepaged/65 is trying to acquire lock:
[ 291.813614] (fs_reclaim){+.+.}, at: [<000000009263bd20>]
fs_reclaim_acquire+0x12/0x40
[ 291.814972]
[ 291.814972] but task is already holding lock:
[ 291.815912] (fs_reclaim){+.+.}, at: [<000000009263bd20>]
fs_reclaim_acquire+0x12/0x40
[ 291.817263]
[ 291.817263] other info that might help us debug this:
[ 291.818355] Possible unsafe locking scenario:
[ 291.818355]
[ 291.819348] CPU0
[ 291.819743] ----
[ 291.820121] lock(fs_reclaim);
[ 291.820689] lock(fs_reclaim);
[ 291.821223]
[ 291.821223] *** DEADLOCK ***
[ 291.821223]
[ 291.822224] May be due to missing lock nesting notation
[ 291.822224]
[ 291.823411] 1 lock held by khugepaged/65:
[ 291.824048] #0: (fs_reclaim){+.+.}, at: [<000000009263bd20>]
fs_reclaim_acquire+0x12/0x40
[ 291.825480]
[ 291.825480] stack backtrace:
[ 291.826155] CPU: 4 PID: 65 Comm: khugepaged Not tainted
4.15.0-rc2-327.58.59.16.x86_64.debug+ #8
[ 291.827696] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
BIOS 1.9.3-1.fc25 04/01/2014
[ 291.829111] Call Trace:
[ 291.829560] dump_stack+0x7c/0xbf
[ 291.830072] __lock_acquire+0x8d6/0x1220
[ 291.830837] lock_acquire+0xc9/0x220
[ 291.831425] ? fs_reclaim_acquire+0x12/0x40
[ 291.832110] ? alloc_extent_state+0x21/0x1c0
[ 291.832824] fs_reclaim_acquire+0x35/0x40
[ 291.833476] ? fs_reclaim_acquire+0x12/0x40
[ 291.834114] kmem_cache_alloc+0x29/0x320
[ 291.834777] alloc_extent_state+0x21/0x1c0
[ 291.835390] __clear_extent_bit+0x2a5/0x3b0
[ 291.836079] try_release_extent_mapping+0x17c/0x200
[ 291.836868] __btrfs_releasepage+0x30/0x90
[ 291.837519] shrink_page_list+0x80d/0xf20
[ 291.838158] shrink_inactive_list+0x250/0x710
[ 291.838875] ? rcu_read_lock_sched_held+0x9b/0xb0
[ 291.839666] shrink_node_memcg+0x358/0x790
[ 291.840282] ? mem_cgroup_iter+0x98/0x530
[ 291.840872] shrink_node+0xe5/0x310
[ 291.841387] do_try_to_free_pages+0xe8/0x390
[ 291.842013] try_to_free_pages+0x146/0x3d0
[ 291.842620] __alloc_pages_slowpath+0x3d1/0xce1
[ 291.843290] __alloc_pages_nodemask+0x411/0x450
[ 291.843989] khugepaged_alloc_page+0x39/0x80
[ 291.844626] collapse_huge_page+0x78/0x9a0
[ 291.845381] ? khugepaged_scan_mm_slot+0x932/0xfa0
[ 291.846113] khugepaged_scan_mm_slot+0x953/0xfa0
[ 291.846838] ? khugepaged+0x130/0x5a0
[ 291.847388] khugepaged+0x2e0/0x5a0
[ 291.848019] ? remove_wait_queue+0x60/0x60
[ 291.848678] kthread+0x141/0x180
[ 291.849239] ? khugepaged_scan_mm_slot+0xfa0/0xfa0
[ 291.849938] ? kthread_stop+0x300/0x300
[ 291.850514] ret_from_fork+0x24/0x30
