From a297b2fcee461e40df763e179cbbfba5a9e572d2 Mon Sep 17 00:00:00 2001 From: Xiaoguang Wang Date: Sun, 10 Feb 2019 23:53:21 -0500 Subject: [PATCH] ext4: unlock unused_pages timely when doing writeback 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 Signed-off-by: Theodore Ts'o --- 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 dd4641f3cdb9..9c3402ec85bc 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -2829,12 +2829,12 @@ retry: 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; @@ -2902,10 +2902,11 @@ retry: 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 -- 2.11.0