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

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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 <[email protected]>
Cc: Konrad Rzeszutek Wilk <[email protected]>
Cc: Seth Jennings <[email protected]>
Cc: Dan Streetman <[email protected]>
Cc: Minchan Kim <[email protected]>
Cc: Bob Liu <[email protected]>
Cc: <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
This commit is contained in:
Weijie Yang 2014-12-02 15:59:25 -08:00 • committed by Linus Torvalds
commit fb993fa1a2
1 changed files with 3 additions and 1 deletions
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4
mm/frontswap.c
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@ -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 */