ocfs2: fix the end cluster offset of FIEMAP
authorJie Liu <jeff.liu@oracle.com>
Wed, 11 Sep 2013 21:20:05 +0000 (14:20 -0700)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Fri, 27 Sep 2013 00:15:50 +0000 (17:15 -0700)
commit55ee351dc444224f7bb9697a98b2d06e8625f491
treefa356512517c9cc95313eb2471151b0ce1a7a85c
parent4013fc200b4df078b77d2fc95de3446c65a9957d
ocfs2: fix the end cluster offset of FIEMAP

commit 28e8be31803b19d0d8f76216cb11b480b8a98bec upstream.

Call fiemap ioctl(2) with given start offset as well as an desired mapping
range should show extents if possible.  However, we somehow figure out the
end offset of mapping via 'mapping_end -= cpos' before iterating the
extent records which would cause problems if the given fiemap length is
too small to a cluster size, e.g,

Cluster size 4096:
debugfs.ocfs2 1.6.3
        Block Size Bits: 12   Cluster Size Bits: 12

The extended fiemap test utility From David:
https://gist.github.com/anonymous/6172331

# dd if=/dev/urandom of=/ocfs2/test_file bs=1M count=1000
# ./fiemap /ocfs2/test_file 4096 10
start: 4096, length: 10
File /ocfs2/test_file has 0 extents:
# Logical          Physical         Length           Flags
^^^^^ <-- No extent is shown

In this case, at ocfs2_fiemap(): cpos == mapping_end == 1. Hence the
loop of searching extent records was not executed at all.

This patch remove the in question 'mapping_end -= cpos', and loops
until the cpos is larger than the mapping_end as usual.

# ./fiemap /ocfs2/test_file 4096 10
start: 4096, length: 10
File /ocfs2/test_file has 1 extents:
# Logical          Physical         Length           Flags
0: 0000000000000000 0000000056a01000 0000000006a00000 0000

Signed-off-by: Jie Liu <jeff.liu@oracle.com>
Reported-by: David Weber <wb@munzinger.de>
Tested-by: David Weber <wb@munzinger.de>
Cc: Sunil Mushran <sunil.mushran@gmail.com>
Cc: Mark Fashen <mfasheh@suse.de>
Cc: Joel Becker <jlbec@evilplan.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
fs/ocfs2/extent_map.c