tree 39a01022ed2294f0acc94b45554c9a292db671dc
parent 6d19c42b7cf81c39632b6d4dbc514e8449bcd346
author Curt Wohlgemuth <curtw@google.com> 1274036400 -0400
committer Theodore Ts'o <tytso@mit.edu> 1274036400 -0400

ext4: check for a good block group before loading buddy pages

This adds a new field in ext4_group_info to cache the largest available
block range in a block group; and don't load the buddy pages until *after*
we've done a sanity check on the block group.

With large allocation requests (e.g., fallocate(), 8MiB) and relatively full
partitions, it's easy to have no block groups with a block extent large
enough to satisfy the input request length.  This currently causes the loop
during cr == 0 in ext4_mb_regular_allocator() to load the buddy bitmap pages
for EVERY block group.  That can be a lot of pages.  The patch below allows
us to call ext4_mb_good_group() BEFORE we load the buddy pages (although we
have check again after we lock the block group).

Addresses-Google-Bug: #2578108
Addresses-Google-Bug: #2704453

Signed-off-by: Curt Wohlgemuth <curtw@google.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>