Commit 515f4a03 authored Jan 06, 2009 by Nick Piggin Committed by Linus Torvalds Jan 06, 2009

mm: write_cache_pages optimise page cleaning



In write_cache_pages, if we get stuck behind another process that is
cleaning pages, we will be forced to wait for them to finish, then perform
our own writeout (if it was redirtied during the long wait), then wait for
that.

If a page under writeout is still clean, we can skip waiting for it (if
we're part of a data integrity sync, we'll be waiting for all writeout
pages afterwards, so we'll still be waiting for the other guy's write
that's cleaned the page).

Signed-off-by: Nick Piggin <npiggin@suse.de>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Dave Chinner <david@fromorbit.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 5a3d5c98

mm/page-writeback.c

+13 −4

Original line number	Diff line number	Diff line
		@@ -945,11 +945,20 @@ continue_unlock:
		goto continue_unlock;
		}

		if (!PageDirty(page)) {
		/* someone wrote it for us */
		goto continue_unlock;
		}

		if (PageWriteback(page)) {
		if (wbc->sync_mode != WB_SYNC_NONE)
		wait_on_page_writeback(page);
		else
		goto continue_unlock;
		}

		if (PageWriteback(page) \|\|
		!clear_page_dirty_for_io(page))
		BUG_ON(PageWriteback(page));
		if (!clear_page_dirty_for_io(page))
		goto continue_unlock;

		ret = (*writepage)(page, wbc, data);

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