src/patches/suse-2.6.27.39/patches.fixes/0006-md-never-clear-bit-from-the-write-intent-bitmap-when.patch

   1 From d0a4bb492772ce5c4bdfba3744a99ed6f6fb238f Mon Sep 17 00:00:00 2001
   2 From: NeilBrown <neilb@suse.de>
   3 Date: Tue, 31 Mar 2009 14:27:02 +1100
   4 Subject: [PATCH] md: never clear bit from the write-intent bitmap when the array is degraded.
   5
   6 It is safe to clear a bit from the write-intent bitmap for a raid1
   7 if we know the data has been written to all devices, which is
   8 what the current test does.
   9
  10 But it is not always safe to update the 'events_cleared' counter in
  11 that case.  This is because one request could complete successfully
  12 after some other request has partially failed.
  13
  14 So simply disable the clearing and updating of events_cleared whenever
  15 the array is degraded.  This might end up not clearing some bits that
  16 could safely be cleared, but it is safest approach.
  17
  18 Note that the bug fixed here did not risk corrupting data by letting
  19 the array get out-of-sync.  Rather it meant that when a device is
  20 removed and re-added to the array, it might incorrectly require a full
  21 recovery rather than just recovering based on the bitmap.
  22
  23 Signed-off-by: NeilBrown <neilb@suse.de>
  24 ---
  25  drivers/md/bitmap.c |    3 +++
  26  1 file changed, 3 insertions(+)
  27
  28 --- a/drivers/md/bitmap.c
  29 +++ b/drivers/md/bitmap.c
  30 @@ -1307,6 +1307,9 @@ void bitmap_endwrite(struct bitmap *bitm
  31                 PRINTK(KERN_DEBUG "dec write-behind count %d/%d\n",
  32                   atomic_read(&bitmap->behind_writes), bitmap->max_write_behind);
  33         }
  34 +       if (bitmap->mddev->degraded)
  35 +               /* Never clear bits or update events_cleared when degraded */
  36 +               success = 0;
  37
  38         while (sectors) {
  39                 int blocks;