mm: write_cache_pages terminate quickly (d5482cdf) · Commits · 戴 / test

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:

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>

mm/page-writeback.c

+16 −16

Original line number	Diff line number	Diff line
		@@ -911,15 +911,24 @@ retry:
		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 @@ continue_unlock:
		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;

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