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Commit d5482cdf authored by Nick Piggin's avatar Nick Piggin Committed by Linus Torvalds
Browse files

mm: write_cache_pages terminate quickly 



Terminate the write_cache_pages loop upon encountering the first page past
end, without locking the page.  Pages cannot have their index change when
we have a reference on them (truncate, eg truncate_inode_pages_range
performs the same check without the page lock).

Signed-off-by: default avatarNick Piggin <npiggin@suse.de>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Dave Chinner <david@fromorbit.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 515f4a03

mm/page-writeback.c

+16 −16
Original line number Diff line number Diff line
@@ -911,15 +911,24 @@ int write_cache_pages(struct address_space *mapping, 
		for (i = 0; i < nr_pages; i++) {

			struct page *page = pvec.pages[i];



			done_index = page->index + 1;



			/*

			 * At this point we hold neither mapping->tree_lock nor

			 * lock on the page itself: the page may be truncated or

			 * invalidated (changing page->mapping to NULL), or even

			 * swizzled back from swapper_space to tmpfs file

			 * mapping

			 * At this point, the page may be truncated or

			 * invalidated (changing page->mapping to NULL), or

			 * even swizzled back from swapper_space to tmpfs file

			 * mapping. However, page->index will not change

			 * because we have a reference on the page.

			 */

			if (page->index > end) {

				/*

				 * can't be range_cyclic (1st pass) because

				 * end == -1 in that case.

				 */

				done = 1;

				break;

			}



			done_index = page->index + 1;



			lock_page(page);



			/*
@@ -936,15 +945,6 @@ int write_cache_pages(struct address_space *mapping, 
				continue;

			}



			if (page->index > end) {

				/*

				 * can't be range_cyclic (1st pass) because

				 * end == -1 in that case.

				 */

				done = 1;

				goto continue_unlock;

			}



			if (!PageDirty(page)) {

				/* someone wrote it for us */

				goto continue_unlock;