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Commit 6ddab3b9ebebc88bfdd8107c64f12d7e4480c559

Authored by Peter Zijlstra
Committed by Linus Torvalds
1 parent ca5f9703df
Exists in master and in 7 other branches imx_3.0.35_4.1.0, imx_3.10.17_1.0.1_ga, imx_3.10.53_1.1.0_ga, imx_3.14.28_1.0.0_ga, smarc-imx_3.10.53_1.1.0_ga, smarc-imx_3.14.28_1.0.0_ga, smarc-l5.0.0_1.0.0-ga

[PATCH] mm: swap write failure fixup 

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>

Showing 1 changed file with 20 additions and 1 deletions Side-by-side Diff

... ... @@ -52,8 +52,23 @@
52 52 if (bio->bi_size)
53 53 return 1;
54 54  
55   - if (!uptodate)
  55 + if (!uptodate) {
56 56 SetPageError(page);
  57 + /*
  58 + * We failed to write the page out to swap-space.
  59 + * Re-dirty the page in order to avoid it being reclaimed.
  60 + * Also print a dire warning that things will go BAD (tm)
  61 + * very quickly.
  62 + *
  63 + * Also clear PG_reclaim to avoid rotate_reclaimable_page()
  64 + */
  65 + set_page_dirty(page);
  66 + printk(KERN_ALERT "Write-error on swap-device (%u:%u:%Lu)\n",
  67 + imajor(bio->bi_bdev->bd_inode),
  68 + iminor(bio->bi_bdev->bd_inode),
  69 + (unsigned long long)bio->bi_sector);
  70 + ClearPageReclaim(page);
  71 + }
57 72 end_page_writeback(page);
58 73 bio_put(bio);
59 74 return 0;
... ... @@ -70,6 +85,10 @@
70 85 if (!uptodate) {
71 86 SetPageError(page);
72 87 ClearPageUptodate(page);
  88 + printk(KERN_ALERT "Read-error on swap-device (%u:%u:%Lu)\n",
  89 + imajor(bio->bi_bdev->bd_inode),
  90 + iminor(bio->bi_bdev->bd_inode),
  91 + (unsigned long long)bio->bi_sector);
73 92 } else {
74 93 SetPageUptodate(page);
75 94 }