From mboxrd@z Thu Jan 1 00:00:00 1970 From: alex chen Date: Wed, 13 Dec 2017 15:49:51 +0800 Subject: [Ocfs2-devel] [PATCH v2] ocfs2: using the OCFS2_XATTR_ROOT_SIZE macro in ocfs2_reflink_xattr_header() In-Reply-To: <20171212144747.f35e16dfcd2a0b90c18e0479@linux-foundation.org> References: <5A2E2488.70301@huawei.com> <20171212144747.f35e16dfcd2a0b90c18e0479@linux-foundation.org> Message-ID: <5A30DB9F.6040506@huawei.com> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: ocfs2-devel@oss.oracle.com Hi Andrew, Thanks for your suggestion. On 2017/12/13 6:47, Andrew Morton wrote: > On Mon, 11 Dec 2017 14:24:08 +0800 alex chen wrote: > >> Using the OCFS2_XATTR_ROOT_SIZE macro improves the readability of the code. >> >> Signed-off-by: Alex Chen >> Reviewed-by: Jun Piao >> --- >> fs/ocfs2/xattr.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/fs/ocfs2/xattr.c b/fs/ocfs2/xattr.c >> index 5fdf269..ca3b61a 100644 >> --- a/fs/ocfs2/xattr.c >> +++ b/fs/ocfs2/xattr.c >> @@ -6415,7 +6415,7 @@ static int ocfs2_reflink_xattr_header(handle_t *handle, >> * and then insert the extents one by one. >> */ >> if (xv->xr_list.l_tree_depth) { >> - memcpy(new_xv, &def_xv, sizeof(def_xv)); >> + memcpy(new_xv, &def_xv, OCFS2_XATTR_ROOT_SIZE); >> vb->vb_xv = new_xv; >> vb->vb_bh = value_bh; >> ocfs2_init_xattr_value_extent_tree(&data_et, > > OK. > > But what's wrong with > > *new_xv = def_xv; > > ? The type of new_xv is 'ocfs2_xattr_value_root' and the type of def_xv is 'ocfs2_xattr_def_value_root'. The length of def_xv is larger than that of new_xv. We initialize the new_xv to the empty default value root which have one extent record. If we use method you describe above to copy, we may missed a copy of one extent record. Thanks, Alex > > That gets typechecked and the compiler may be able to perform > some optimizations... > > > . >