ext4: trim allocation requests to group size

commit cd648b8a8fd5071d232242d5ee7ee3c0815776af upstream.

If filesystem groups are artifically small (using parameter -g to
mkfs.ext4), ext4_mb_normalize_request() can result in a request that is
larger than a block group. Trim the request size to not confuse
allocation code.

Reported-by: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 7 insertions, 0 deletions

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 7ae43c59bc79..2e9fc7a61048 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -3123,6 +3123,13 @@ ext4_mb_normalize_request(struct ext4_allocation_context *ac,
         if (ar->pright && start + size - 1 >= ar->lright)
                 size -= start + size - ar->lright;
 
+        /*
+         * Trim allocation request for filesystems with artificially small
+         * groups.
+         */
+        if (size > EXT4_BLOCKS_PER_GROUP(ac->ac_sb))
+                size = EXT4_BLOCKS_PER_GROUP(ac->ac_sb);
+
         end = start + size;
 
         /* check we don't cross already preallocated blocks */