btrfs: properly access unaligned checksum buffer
authorDavid Sterba <dave@jikos.cz>
Fri, 18 Mar 2011 22:56:43 +0000 (22:56 +0000)
committerroot <Chris Mason chris.mason@oracle.com>
Mon, 28 Mar 2011 09:37:36 +0000 (05:37 -0400)
commit7e75bf3ff3a716d7b21d8fb43bf823115801c1e9
tree98509e562fe9577001f60e1035283c5cb4e076ea
parentdb5b493ac78e46c7b6bad22cd25d8041564cd8ea
btrfs: properly access unaligned checksum buffer

On Fri, Mar 18, 2011 at 11:56:53AM -0400, Chris Mason wrote:
> Thanks for fielding this one.  Does put_unaligned_le32 optimize away on
> platforms with efficient access?  It would be great if we didn't need
> the #ifdef.

(quicktest: assembly output is same for put_unaligned_le32 and direct
assignment on my x86_64)
I was originally following examples in
Documentation/unaligned-memory-access.txt. From other code it seems to me that
the define CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS is intended for larger
portions of code. Macros/wrappers for {put,get}_unaligned* are chosen via
arch/<arch>/include/asm/unaligned.h accordingly, therefore it's safe to use
put_unaligned_le32 without the ifdef.

dave

Signed-off-by: Chris Mason <chris.mason@oracle.com>
fs/btrfs/disk-io.c