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authorJoel Becker <joel.becker@oracle.com>2008-11-25 19:00:15 -0800
committerMark Fasheh <mfasheh@suse.com>2009-01-05 08:40:27 -0800
commit2b656c1d6fc5ba7791a360766780a212faed5705 (patch)
treeea1ec010e7c3af013f3fe2cbbbed180ad20b73b8
parent15d609293d1954465a4788b9b182214323c6a2a1 (diff)
ocfs2: Explain t_is_new in ocfs2_cp_xattr_cluster().
I was unsure of the JOURNAL_ACCESS parameters in ocfs2_cp_xattr_cluster(). They're based on the function argument 't_is_new', but I couldn't quite figure out how t_is_new mapped to allocation. ocfs2_cp_xattr_cluster() actually overwrites the target, regardless of t_is_new. Well, I just figured it out. So I'm adding a big fat comment for those who come after me. ocfs2_divide_xattr_cluster() has the same behavior. Signed-off-by: Joel Becker <joel.becker@oracle.com> Signed-off-by: Mark Fasheh <mfasheh@suse.com>
-rw-r--r--fs/ocfs2/xattr.c17
1 files changed, 17 insertions, 0 deletions
diff --git a/fs/ocfs2/xattr.c b/fs/ocfs2/xattr.c
index 4dba3475882..5efcf4e85d7 100644
--- a/fs/ocfs2/xattr.c
+++ b/fs/ocfs2/xattr.c
@@ -3747,6 +3747,11 @@ static int ocfs2_divide_xattr_bucket(struct inode *inode,
goto out;
}
+ /*
+ * Hey, if we're overwriting t_bucket, what difference does
+ * ACCESS_CREATE vs ACCESS_WRITE make? See the comment in the
+ * same part of ocfs2_cp_xattr_bucket().
+ */
ret = ocfs2_xattr_bucket_journal_access(handle, t_bucket,
new_bucket_head ?
OCFS2_JOURNAL_ACCESS_CREATE :
@@ -3918,6 +3923,18 @@ static int ocfs2_cp_xattr_bucket(struct inode *inode,
if (ret)
goto out;
+ /*
+ * Hey, if we're overwriting t_bucket, what difference does
+ * ACCESS_CREATE vs ACCESS_WRITE make? Well, if we allocated a new
+ * cluster to fill, we came here from ocfs2_cp_xattr_cluster(), and
+ * it is really new - ACCESS_CREATE is required. But we also
+ * might have moved data out of t_bucket before extending back
+ * into it. ocfs2_add_new_xattr_bucket() can do this - its call
+ * to ocfs2_add_new_xattr_cluster() may have created a new extent
+ * and copied out the end of the old extent. Then it re-extends
+ * the old extent back to create space for new xattrs. That's
+ * how we get here, and the bucket isn't really new.
+ */
ret = ocfs2_xattr_bucket_journal_access(handle, t_bucket,
t_is_new ?
OCFS2_JOURNAL_ACCESS_CREATE :