From: Liu Bo <bo.li.liu@oracle.com>
Date: Thu, 7 Sep 2017 11:22:21 -0600
Subject: Btrfs: do not make defrag wait on async_delalloc_pages
Git-commit: 80e03a2c512bd78858c130d6fe3b11982a61c0c5
Patch-mainline: v4.15-rc1
References: bsc#1135481
By setting compression for a defrag task, the task will start IO at
the end of defrag.
After the combo of filemap_flush(), we've already made sure that
dirty pages have made progress via async compress thread because the
second filemap_flush() will wait for page lock, which won't be
unlocked until those pages have been marked as writeback and ordered
extents have been queued.
And this is for per-inode defrag, it's not helpful to wait on a global
%async_delalloc_pages and %nr_async_submits from fs_info.
Although waiting on %nr_async_submits means that all bios are
submitted down to per-device schedule IO lists, it doesn't wait for
their completions, thus users still need to do fsync/sync to make sure
the data is on disk. While with this change, it makes sure that pages
are marked with writeback bits and will be submitted asynchronously
shortly, therefore, the behavior of defrag option '-c' remains unchanged.
Signed-off-by: Liu Bo <bo.li.liu@oracle.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Acked-by: Nikolay Borisov <nborisov@suse.com>
---
fs/btrfs/ioctl.c | 15 ---------------
1 file changed, 15 deletions(-)
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -1451,21 +1451,6 @@ int btrfs_defrag_file(struct inode *inod
filemap_flush(inode->i_mapping);
}
- if ((range->flags & BTRFS_DEFRAG_RANGE_COMPRESS)) {
- /* the filemap_flush will queue IO into the worker threads, but
- * we have to make sure the IO is actually started and that
- * ordered extents get created before we return
- */
- atomic_inc(&fs_info->async_submit_draining);
- while (atomic_read(&fs_info->nr_async_submits) ||
- atomic_read(&fs_info->async_delalloc_pages)) {
- wait_event(fs_info->async_submit_wait,
- (atomic_read(&fs_info->nr_async_submits) == 0 &&
- atomic_read(&fs_info->async_delalloc_pages) == 0));
- }
- atomic_dec(&fs_info->async_submit_draining);
- }
-
if (range->compress_type == BTRFS_COMPRESS_LZO) {
btrfs_set_fs_incompat(fs_info, COMPRESS_LZO);
} else if (range->compress_type == BTRFS_COMPRESS_ZSTD) {