In mpage_add_bh_to_extent(), when accumulated extents length is greater than MAX_WRITEPAGES_EXTENT_LEN or buffer head's b_stat is not equal, we will not continue to search unmapped area for this page, but note this page is locked, and will only be unlocked in mpage_release_unused_pages() after ext4_io_submit, if io also is throttled by blk-throttle or similar io qos, we will hold this page locked for a while, it's unnecessary. I think the best fix is to refactor mpage_add_bh_to_extent() to let it return some hints whether to unlock this page, but given that we will improve dioread_nolock later, we can let it done later, so currently the simple fix would just call mpage_release_unused_pages() before ext4_io_submit(). Signed-off-by: Xiaoguang Wang <xiaoguang.wang@xxxxxxxxxxxxxxxxx> --- fs/ext4/inode.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c index 34d7e0703cc6..83a0d7c76736 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -2836,12 +2836,12 @@ static int ext4_writepages(struct address_space *mapping, goto unplug; } ret = mpage_prepare_extent_to_map(&mpd); + /* Unlock pages we didn't use */ + mpage_release_unused_pages(&mpd, false); /* Submit prepared bio */ ext4_io_submit(&mpd.io_submit); ext4_put_io_end_defer(mpd.io_submit.io_end); mpd.io_submit.io_end = NULL; - /* Unlock pages we didn't use */ - mpage_release_unused_pages(&mpd, false); if (ret < 0) goto unplug; @@ -2909,10 +2909,11 @@ static int ext4_writepages(struct address_space *mapping, handle = NULL; mpd.do_map = 0; } - /* Submit prepared bio */ - ext4_io_submit(&mpd.io_submit); /* Unlock pages we didn't use */ mpage_release_unused_pages(&mpd, give_up_on_write); + /* Submit prepared bio */ + ext4_io_submit(&mpd.io_submit); + /* * Drop our io_end reference we got from init. We have * to be careful and use deferred io_end finishing if -- 2.17.2
