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Commit f275635e authored by Yan, Zheng's avatar Yan, Zheng Committed by Ilya Dryomov
Browse files

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: default avatar"Yan, Zheng" <zyan@redhat.com>
Signed-off-by: default avatarIlya Dryomov <idryomov@gmail.com>
parent 7e1ee54a

fs/ceph/addr.c

+24 −0
Original line number Diff line number Diff line
@@ -1165,6 +1165,30 @@ static int ceph_writepages_start(struct address_space *mapping, 
		/* 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;