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SubjectRe: [PATCH] check name_len before down_read xattr_sem and sb_read in ext2_xattr_get
On Mon, Jul 12, 2010 at 10:29:09PM +0800, crosslonelyover wrote:
> Hi,
> I walked through ext2_xattr_get, and felt that we can
> do some optimization on it. For name_len check, it's done
> after down xattr_sem and sb_read, both of which are time
> consuming operation compared with strlen:
> down_read(&EXT2_I(inode)->xattr_sem);
> ...
> bh = sb_bread(inode->i_sb, EXT2_I(inode)->i_file_acl);
> ...
> /* find named attribute */
> name_len = strlen(name);
>
> error = -ERANGE;
> if (name_len > 255)
> goto cleanup;
>
> Most of the case, you'll get one valid block, but if the
> name len > 255, then the xattr_sem down and sb_bread operation
> can be seen as a waste of time. So I think we'd better do
> name len check as early as possible.
> Following is my patch, and it's against 2.6.35-rc4.
> Please check it.
>
> Signed-off-by: Wang Sheng-Hui <crosslonelyover@gmail.com>
> ---
> fs/ext2/xattr.c | 12 +++++++-----
> 1 files changed, 7 insertions(+), 5 deletions(-)

For what it's worth, this change looks OK to me.

Reviewed-by: Dan Carpenter <error27@gmail.com>

regards,
dan carpenter




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