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[PATCH] mm: swap write failure fixup

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Currently we can silently drop data if the write to swap failed.  It
usually doesn't result in data-corruption because on page-in the process
will receive SIGBUS (assuming write-failure implies read-failure).

This assumption might or might not be valid.

This patch will avoid the page being discarded after a failed write.  But
will print a warning the sysadmin _should_ take to heart, if a lot of swap
space becomes un-writeable, OOM is not far off.

Tested by making the write fail 'randomly' once every 50 writes or so.

[akpm@osdl.org: printk warning fix]
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Peter Zijlstra 2006-09-25 23:31:26 -07:00 committed by Linus Torvalds
parent ca5f9703df
commit 6ddab3b9eb
1 changed files with 20 additions and 1 deletions
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21
mm/page_io.c
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@ -52,8 +52,23 @@ static int end_swap_bio_write(struct bio *bio, unsigned int bytes_done, int err)
if (bio->bi_size) if (bio->bi_size)
return 1; return 1;
if (!uptodate) if (!uptodate) {
SetPageError(page); SetPageError(page);
/*
* We failed to write the page out to swap-space.
* Re-dirty the page in order to avoid it being reclaimed.
* Also print a dire warning that things will go BAD (tm)
* very quickly.
*
* Also clear PG_reclaim to avoid rotate_reclaimable_page()
*/
set_page_dirty(page);
printk(KERN_ALERT "Write-error on swap-device (%u:%u:%Lu)\n",
imajor(bio->bi_bdev->bd_inode),
iminor(bio->bi_bdev->bd_inode),
(unsigned long long)bio->bi_sector);
ClearPageReclaim(page);
}
end_page_writeback(page); end_page_writeback(page);
bio_put(bio); bio_put(bio);
return 0; return 0;
@ -70,6 +85,10 @@ static int end_swap_bio_read(struct bio *bio, unsigned int bytes_done, int err)
if (!uptodate) { if (!uptodate) {
SetPageError(page); SetPageError(page);
ClearPageUptodate(page); ClearPageUptodate(page);
printk(KERN_ALERT "Read-error on swap-device (%u:%u:%Lu)\n",
imajor(bio->bi_bdev->bd_inode),
iminor(bio->bi_bdev->bd_inode),
(unsigned long long)bio->bi_sector);
} else { } else {
SetPageUptodate(page); SetPageUptodate(page);
} }