From f275635ee0b6641151dfaf07b901d7c8d4d8e987 Mon Sep 17 00:00:00 2001 From: "Yan, Zheng" Date: Fri, 1 Sep 2017 17:03:16 +0800 Subject: [PATCH] ceph: wait on writeback after writing snapshot data In sync mode, writepages() needs to write all dirty pages. But it can only write dirty pages associated with the oldest snapc. To write dirty pages associated with next snapc, it needs to wait until current writes complete. Without this wait, writepages() keeps looking up dirty pages, but the found dirty pages are not writeable. It wastes CPU time. Signed-off-by: "Yan, Zheng" Signed-off-by: Ilya Dryomov --- fs/ceph/addr.c | 24 ++++++++++++++++++++++++ 1 file changed, 24 insertions(+) diff --git a/fs/ceph/addr.c b/fs/ceph/addr.c index 1ffdb903eb79..b3e3edc09d80 100644 --- a/fs/ceph/addr.c +++ b/fs/ceph/addr.c @@ -1165,6 +1165,30 @@ release_pvec_pages: /* more to do; loop back to beginning of file */ dout("writepages looping back to beginning of file\n"); end = start_index - 1; /* OK even when start_index == 0 */ + + /* to write dirty pages associated with next snapc, + * we need to wait until current writes complete */ + if (wbc->sync_mode != WB_SYNC_NONE && + start_index == 0 && /* all dirty pages were checked */ + !ceph_wbc.head_snapc) { + struct page *page; + unsigned i, nr; + index = 0; + while ((index <= end) && + (nr = pagevec_lookup_tag(&pvec, mapping, &index, + PAGECACHE_TAG_WRITEBACK, + PAGEVEC_SIZE))) { + for (i = 0; i < nr; i++) { + page = pvec.pages[i]; + if (page_snap_context(page) != snapc) + continue; + wait_on_page_writeback(page); + } + pagevec_release(&pvec); + cond_resched(); + } + } + start_index = 0; index = 0; goto retry; -- 2.20.1