2010/7/22 Jan Kara <jack@xxxxxxx>: >> 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@xxxxxxxxx> >> --- >> fs/ext2/xattr.c | 12 +++++++----- >> 1 files changed, 7 insertions(+), 5 deletions(-) >> >> diff --git a/fs/ext2/xattr.c b/fs/ext2/xattr.c >> index 7c39157..0b94d61 100644 >> --- a/fs/ext2/xattr.c >> +++ b/fs/ext2/xattr.c >> @@ -161,6 +161,13 @@ ext2_xattr_get(struct inode *inode, int name_index, const char *name, >> >> if (name == NULL) >> return -EINVAL; >> + >> + /* find named attribute */ >> + name_len = strlen(name); >> + error = -ERANGE; >> + if (name_len > 255) >> + goto cleanup; > But you cannot go to cleanup here because you don't hold xattr_sem... > Sorry, I'm a little confused by your words. The patch just checks name_len, and it doesn't need xattr_sem. -- Thanks and Best Regards, shenghui -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
