From: Curt Wohlgemuth <curtw@google.com>
Date: Sun, 16 May 2010 19:00:00 +0000 (-0400)
Subject: ext4: check for a good block group before loading buddy pages
X-Git-Tag: v2.6.35-rc1~39^2~17
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=8a57d9d61a6e361c7bb159dda797672c1df1a691;p=pandora-kernel.git

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>
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