src/patches/suse-2.6.27.25/patches.drivers/bdev-resize-call-flush_disk

   1 Subject: Call flush_disk() after detecting an online resize.
   2 From: Andrew Patterson <andrew.patterson@hp.com>
   3 Date: Thu Oct 9 08:56:13 2008 +0200:
   4 Git: 608aeef17a91747d6303de4df5e2c2e6899a95e8
   5 References: FATE#302348,FATE#303786
   6
   7 We call flush_disk() to make sure the buffer cache for the disk is
   8 flushed after a disk resize. There are two resize cases, growing and
   9 shrinking. Given that users can shrink/then grow a disk before
  10 revalidate_disk() is called, we treat the grow case identically to
  11 shrinking. We need to flush the buffer cache after an online shrink
  12 because, as James Bottomley puts it,
  13
  14      The two use cases for shrinking I can see are
  15
  16      1. planned: the fs is already shrunk to within the new boundaries
  17         and all data is relocated, so invalidate is fine (any dirty
  18         buffers that might exist in the shrunk region are there only
  19         because they were relocated but not yet written to their
  20         original location).
  21      2. unplanned:  In this case, the fs is probably toast, so whether
  22         we invalidate or not isn't going to make a whole lot of
  23         difference; it's still going to try to read or write from
  24         sectors beyond the new size and get I/O errors.
  25
  26 Immediately invalidating shrunk disks will cause errors for outstanding
  27 I/Os for reads/write beyond the new end of the disk to be generated
  28 earlier then if we waited for the normal buffer cache operation. It also
  29 removes a potential security hole where we might keep old data around
  30 from beyond the end of the shrunk disk if the disk was not invalidated.
  31
  32 Signed-off-by: Andrew Patterson <andrew.patterson@hp.com>
  33 Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
  34 Signed-off-by: Hannes Reinecke <hare@suse.de>
  35 ---
  36  fs/block_dev.c |    1 +
  37  1 file changed, 1 insertion(+)
  38
  39 --- a/fs/block_dev.c
  40 +++ b/fs/block_dev.c
  41 @@ -918,6 +918,7 @@ void check_disk_size_change(struct gendi
  42                        "%s: detected capacity change from %lld to %lld\n",
  43                        name, bdev_size, disk_size);
  44                 i_size_write(bdev->bd_inode, disk_size);
  45 +               flush_disk(bdev);
  46         }
  47  }
  48  EXPORT_SYMBOL(check_disk_size_change);