ext4: limit group search loop for non-extent files
authorLachlan McIlroy <lmcilroy@redhat.com>
Mon, 6 May 2013 03:10:00 +0000 (23:10 -0400)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Sun, 19 May 2013 17:54:40 +0000 (10:54 -0700)
commitd556c9b5a98ceee8b1d1d74d7277141da437bc26
treed9a20de60c4911459402911215987a1e85ca890a
parentcba998b9b3799a5d6861a969d7b7d9b4f4f181f6
ext4: limit group search loop for non-extent files

commit e6155736ad76b2070652745f9e54cdea3f0d8567 upstream.

In the case where we are allocating for a non-extent file,
we must limit the groups we allocate from to those below
2^32 blocks, and ext4_mb_regular_allocator() attempts to
do this initially by putting a cap on ngroups for the
subsequent search loop.

However, the initial target group comes in from the
allocation context (ac), and it may already be beyond
the artificially limited ngroups.  In this case,
the limit

if (group == ngroups)
group = 0;

at the top of the loop is never true, and the loop will
run away.

Catch this case inside the loop and reset the search to
start at group 0.

[sandeen@redhat.com: add commit msg & comments]

Signed-off-by: Lachlan McIlroy <lmcilroy@redhat.com>
Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
fs/ext4/mballoc.c