From 80e03a2c512bd78858c130d6fe3b11982a61c0c5 Mon Sep 17 00:00:00 2001 From: Liu Bo Date: Thu, 7 Sep 2017 11:22:21 -0600 Subject: [PATCH] Btrfs: do not make defrag wait on async_delalloc_pages 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 Signed-off-by: David Sterba --- fs/btrfs/ioctl.c | 15 --------------- 1 file changed, 15 deletions(-) diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c index dfc5b4862289..83ccadaf6705 100644 --- a/fs/btrfs/ioctl.c +++ b/fs/btrfs/ioctl.c @@ -1405,21 +1405,6 @@ int btrfs_defrag_file(struct inode *inode, struct file *file, filemap_flush(inode->i_mapping); } - if (do_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) { -- 2.30.2