diff options
| author | Nikolay Borisov <nborisov@suse.com> | 2019-09-04 19:33:58 +0300 |
|---|---|---|
| committer | David Sterba <dsterba@suse.com> | 2019-09-09 14:59:20 +0200 |
| commit | 6af112b11a4bc1b560f60a618ac9c1dcefe9836e (patch) | |
| tree | dd4bc275d6cb2f6fb3ca4cc63a9fa65e070bf6dc /fs/btrfs | |
| parent | 65e99c43e9c2fee1a1f02c100154730fbeae9717 (diff) | |
| download | lwn-6af112b11a4bc1b560f60a618ac9c1dcefe9836e.tar.gz lwn-6af112b11a4bc1b560f60a618ac9c1dcefe9836e.zip | |
btrfs: Relinquish CPUs in btrfs_compare_trees
When doing any form of incremental send the parent and the child trees
need to be compared via btrfs_compare_trees. This can result in long
loop chains without ever relinquishing the CPU. This causes softlockup
detector to trigger when comparing trees with a lot of items. Example
report:
watchdog: BUG: soft lockup - CPU#0 stuck for 24s! [snapperd:16153]
CPU: 0 PID: 16153 Comm: snapperd Not tainted 5.2.9-1-default #1 openSUSE Tumbleweed (unreleased)
Hardware name: QEMU KVM Virtual Machine, BIOS 0.0.0 02/06/2015
pstate: 40000005 (nZcv daif -PAN -UAO)
pc : __ll_sc_arch_atomic_sub_return+0x14/0x20
lr : btrfs_release_extent_buffer_pages+0xe0/0x1e8 [btrfs]
sp : ffff00001273b7e0
Call trace:
__ll_sc_arch_atomic_sub_return+0x14/0x20
release_extent_buffer+0xdc/0x120 [btrfs]
free_extent_buffer.part.0+0xb0/0x118 [btrfs]
free_extent_buffer+0x24/0x30 [btrfs]
btrfs_release_path+0x4c/0xa0 [btrfs]
btrfs_free_path.part.0+0x20/0x40 [btrfs]
btrfs_free_path+0x24/0x30 [btrfs]
get_inode_info+0xa8/0xf8 [btrfs]
finish_inode_if_needed+0xe0/0x6d8 [btrfs]
changed_cb+0x9c/0x410 [btrfs]
btrfs_compare_trees+0x284/0x648 [btrfs]
send_subvol+0x33c/0x520 [btrfs]
btrfs_ioctl_send+0x8a0/0xaf0 [btrfs]
btrfs_ioctl+0x199c/0x2288 [btrfs]
do_vfs_ioctl+0x4b0/0x820
ksys_ioctl+0x84/0xb8
__arm64_sys_ioctl+0x28/0x38
el0_svc_common.constprop.0+0x7c/0x188
el0_svc_handler+0x34/0x90
el0_svc+0x8/0xc
Fix this by adding a call to cond_resched at the beginning of the main
loop in btrfs_compare_trees.
Fixes: 7069830a9e38 ("Btrfs: add btrfs_compare_trees function")
CC: stable@vger.kernel.org # 4.4+
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Diffstat (limited to 'fs/btrfs')
| -rw-r--r-- | fs/btrfs/send.c | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/fs/btrfs/send.c b/fs/btrfs/send.c index f856d6ca3771..f3215028235c 100644 --- a/fs/btrfs/send.c +++ b/fs/btrfs/send.c @@ -6757,6 +6757,7 @@ static int btrfs_compare_trees(struct btrfs_root *left_root, advance_left = advance_right = 0; while (1) { + cond_resched(); if (advance_left && !left_end_reached) { ret = tree_advance(left_path, &left_level, left_root_level, |