ext4: correctly calculate number of blocks for fiemap
commitdc1429f8aef9acfa88920311d045c54bc97b062f
authorLeonard Michlmayr <leonard.michlmayr@gmail.com>
Thu, 4 Mar 2010 22:07:28 +0000 (4 17:07 -0500)
committerGreg Kroah-Hartman <gregkh@suse.de>
Wed, 12 May 2010 21:57:10 +0000 (12 14:57 -0700)
treeea0188641592cfb7d6c7d8709aa17f2fcf45f32d
parent4c57ef6ae19a315202f7af060f28d9880fc5d2dd
ext4: correctly calculate number of blocks for fiemap

commit aca92ff6f57c000d1b4523e383c8bd6b8269b8b1 upstream.

ext4_fiemap() rounds the length of the requested range down to
blocksize, which is is not the true number of blocks that cover the
requested region.  This problem is especially impressive if the user
requests only the first byte of a file: not a single extent will be
reported.

We fix this by calculating the last block of the region and then
subtract to find the number of blocks in the extents.

Signed-off-by: Leonard Michlmayr <leonard.michlmayr@gmail.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
fs/ext4/extents.c