| Message ID | 20190904163358.11591-1-nborisov@suse.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | btrfs: Relinquish CPUs in btrfs_compare_trees | expand |
Looks good,
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
On Wed, Sep 04, 2019 at 07:33:58PM +0300, Nikolay Borisov wrote: > 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") > Signed-off-by: Nikolay Borisov <nborisov@suse.com> Reviewed-by: David Sterba <dsterba@suse.com>
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,
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") Signed-off-by: Nikolay Borisov <nborisov@suse.com> --- fs/btrfs/send.c | 1 + 1 file changed, 1 insertion(+)