| Message ID | 20200211053729.20807-1-wqu@suse.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | btrfs: Make balance cancelling response faster | expand |
On Tue, Feb 11, 2020 at 01:37:25PM +0800, Qu Wenruo wrote: > For the canceled balance during relocate_block_group(), we are re-using > the existing error handling path. > It will mark all existing reloc_roots as orphan in prepare_to_merge(), > then queue all of them for cleanup in merge_reloc_roots(). > Thus it shouldn't cause any problem. > > Changelog: > v2: > - Rebased to v5.6-rc1 > There is a small conflicts caused by extra finished stage output. > Other than that, everything is pretty straightforward > > - Add explanation for the error handling path in cover letter. Ah so the text is here, but we want it in the changelog and perhaps in the code too as it's breaking out of a loop that does a lot of things. As further changes are not in code I'll add the patches (without 4th) to for-next for more testing. Thanks.
[PROBLEM] There are quite some users reporting that 'btrfs balance cancel' slow to cancel current running balance, or even doesn't work for certain dead balance loop. With the following script showing how long it takes to fully stop a balance: #!/bin/bash dev=/dev/test/test mnt=/mnt/btrfs umount $mnt &> /dev/null umount $dev &> /dev/null mkfs.btrfs -f $dev mount $dev -o nospace_cache $mnt dd if=/dev/zero bs=1M of=$mnt/large & dd_pid=$! sleep 3 kill -KILL $dd_pid sync btrfs balance start --bg --full $mnt & sleep 1 echo "cancel request" >> /dev/kmsg time btrfs balance cancel $mnt umount $mnt It takes around 7~10s to cancel the running balance in my test environment. [CAUSE] Btrfs uses btrfs_fs_info::balance_cancel_req to record how many cancel request are queued. However that cancelling request is only checked after relocating a block group. That behavior is far from optimal to provide a faster cancelling. [FIX] This patchset will add more cancelling check points, to make cancelling faster. And also, introduce a new error injection points to cover these newly introduced and future check points. For the canceled balance during relocate_block_group(), we are re-using the existing error handling path. It will mark all existing reloc_roots as orphan in prepare_to_merge(), then queue all of them for cleanup in merge_reloc_roots(). Thus it shouldn't cause any problem. Changelog: v2: - Rebased to v5.6-rc1 There is a small conflicts caused by extra finished stage output. Other than that, everything is pretty straightforward - Add explanation for the error handling path in cover letter. Qu Wenruo (4): btrfs: relocation: Introduce error injection points for cancelling balance btrfs: relocation: Check cancel request after each data page read btrfs: relocation: Check cancel request after each extent found btrfs: relocation: Work around dead relocation stage loop fs/btrfs/ctree.h | 1 + fs/btrfs/relocation.c | 24 ++++++++++++++++++++++++ fs/btrfs/volumes.c | 2 +- 3 files changed, 26 insertions(+), 1 deletion(-)