dm: use i_size_read

Use i_size_read() instead of reading i_size.

If someone changes the size of the device simultaneously, i_size_read
is guaranteed to return a valid value (either the old one or the new one).

i_size can return some intermediate invalid value (on 32-bit computers
with 64-bit i_size, the reads to both halves of i_size can be interleaved
with updates to i_size, resulting in garbage being returned).

Cc: stable@kernel.org
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

1 files changed, 2 insertions, 1 deletions

diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
index e9a73bb242b0..0e2210c0c168 100644
--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c
@@ -388,7 +388,8 @@ static void close_dev(struct dm_dev_internal *d, struct mapped_device *md)
 static int check_device_area(struct dm_dev_internal *dd, sector_t start,
                              sector_t len)
 {
-        sector_t dev_size = dd->dm_dev.bdev->bd_inode->i_size >> SECTOR_SHIFT;
+        sector_t dev_size = i_size_read(dd->dm_dev.bdev->bd_inode) >>
+                            SECTOR_SHIFT;
 
         if (!dev_size)
                 return 1;