Commit fb993fa1 authored Dec 02, 2014 by Weijie Yang Committed by Linus Torvalds Dec 02, 2014

mm: frontswap: invalidate expired data on a dup-store failure



If a frontswap dup-store failed, it should invalidate the expired page
in the backend, or it could trigger some data corruption issue.
Such as:
 1. use zswap as the frontswap backend with writeback feature
 2. store a swap page(version_1) to entry A, success
 3. dup-store a newer page(version_2) to the same entry A, fail
 4. use __swap_writepage() write version_2 page to swapfile, success
 5. zswap do shrink, writeback version_1 page to swapfile
 6. version_2 page is overwrited by version_1, data corrupt.

This patch fixes this issue by invalidating expired data immediately
when meet a dup-store failure.

Signed-off-by: Weijie Yang <weijie.yang@samsung.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Seth Jennings <sjennings@variantweb.net>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Bob Liu <bob.liu@oracle.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent bc127bda

mm/frontswap.c

+3 −1

Original line number	Diff line number	Diff line
		@@ -244,8 +244,10 @@ int __frontswap_store(struct page *page)
		the (older) page from frontswap
		*/
		inc_frontswap_failed_stores();
		if (dup)
		if (dup) {
		__frontswap_clear(sis, offset);
		frontswap_ops->invalidate_page(type, offset);
		}
		}
		if (frontswap_writethrough_enabled)
		/* report failure so swap also writes to swap device */

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