From: Theodore Ts'o <tytso@mit.edu>
Date: Mon, 23 Feb 2009 11:46:01 +0000 (-0500)
Subject: ext4: Save stack space by removing fake buffer heads
X-Git-Tag: v2.6.30-rc1~416^2~19
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=8dc207c0e7a259e7122ddfaf56b8bbbc3c92d685;p=pandora-kernel.git

ext4: Save stack space by removing fake buffer heads

Struct mpage_da_data and mpage_add_bh_to_extent() use a fake struct
buffer_head which is 104 bytes on an x86_64 system, but only use 24
bytes of the structure.  On systems that use a spinlock for atomic_t,
the stack savings will be even greater.

It turns out that using a fake struct buffer_head doesn't even save
that much code, and it makes the code more confusing since it's not
used as a "real" buffer head.  So just store pass b_size and b_state
in mpage_add_bh_to_extent(), and store b_size, b_state, and b_block_nr
in the mpage_da_data structure.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
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