[PATCH 3.10 009/268] ext4: trim allocation requests to group size

Willy Tarreau
2017-06-19T18:33:52Z

From: Jan Kara <jack@suse.cz>

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: Willy Tarreau <w@1wt.eu>
---
fs/ext4/mballoc.c | 7 +++++++
1 file changed, 7 insertions(+)

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 83ed61a..cba1fc6 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -3063,6 +3063,13 @@ 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 */
--
2.8.0.rc2.1.gbe9624a