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| author | David Sterba <dave@jikos.cz> | 2011-03-18 22:56:43 +0000 |
|---|---|---|
| committer | root <Chris Mason chris.mason@oracle.com> | 2011-03-28 05:37:36 -0400 |
| commit | 7e75bf3ff3a716d7b21d8fb43bf823115801c1e9 (patch) | |
| tree | 98509e562fe9577001f60e1035283c5cb4e076ea | |
| parent | db5b493ac78e46c7b6bad22cd25d8041564cd8ea (diff) | |
| download | blackbird-op-linux-7e75bf3ff3a716d7b21d8fb43bf823115801c1e9.tar.gz blackbird-op-linux-7e75bf3ff3a716d7b21d8fb43bf823115801c1e9.zip | |
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>
| -rw-r--r-- | fs/btrfs/disk-io.c | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c index 00cbb41af660..2bdb124333ab 100644 --- a/fs/btrfs/disk-io.c +++ b/fs/btrfs/disk-io.c @@ -29,6 +29,7 @@ #include <linux/crc32c.h> #include <linux/slab.h> #include <linux/migrate.h> +#include <asm/unaligned.h> #include "compat.h" #include "ctree.h" #include "disk-io.h" @@ -198,7 +199,7 @@ u32 btrfs_csum_data(struct btrfs_root *root, char *data, u32 seed, size_t len) void btrfs_csum_final(u32 crc, char *result) { - *(__le32 *)result = ~cpu_to_le32(crc); + put_unaligned_le32(~crc, result); } /* |
