[PATCH 6/6] xfs: replace the XFS_IOC_GETPARENTS backend

["Darrick J. Wong" <djwong@xxxxxxxxxx>]

From: Darrick J. Wong <djwong@xxxxxxxxxx>

Now that xfs_attr_list can pass local xattr values to the put_listent
function, build a new version of the GETPARENTS backend that supplies a
custom put_listent function to format parent pointer info directly into
the caller's buffer.  This uses a lot less memory and obviates the
iterate list and then grab the values logic, since parent pointers
aren't supposed to have remote values anyway.

Signed-off-by: Darrick J. Wong <djwong@xxxxxxxxxx>
---
 libxfs/xfs_parent.c |   40 ++++++++++++++++++++++++++++++----------
 libxfs/xfs_parent.h |   21 +++++++++++++++++++--
 2 files changed, 49 insertions(+), 12 deletions(-)


diff --git a/libxfs/xfs_parent.c b/libxfs/xfs_parent.c
index 654eaec7..74c7f1f7 100644
--- a/libxfs/xfs_parent.c
+++ b/libxfs/xfs_parent.c
@@ -30,16 +30,6 @@
 
 struct kmem_cache		*xfs_parent_intent_cache;
 
-/* Initializes a xfs_parent_ptr from an xfs_parent_name_rec */
-void
-xfs_init_parent_ptr(struct xfs_parent_ptr		*xpp,
-		    const struct xfs_parent_name_rec	*rec)
-{
-	xpp->xpp_ino = be64_to_cpu(rec->p_ino);
-	xpp->xpp_gen = be32_to_cpu(rec->p_gen);
-	xpp->xpp_diroffset = be32_to_cpu(rec->p_diroffset);
-}
-
 /*
  * Parent pointer attribute handling.
  *
@@ -116,6 +106,36 @@ xfs_init_parent_name_rec(
 	rec->p_diroffset = cpu_to_be32(p_diroffset);
 }
 
+/*
+ * Convert an ondisk parent_name xattr to its incore format.  If @value is
+ * NULL, set @irec->p_namelen to zero and leave @irec->p_name untouched.
+ */
+void
+xfs_parent_irec_from_disk(
+	struct xfs_parent_name_irec	*irec,
+	const struct xfs_parent_name_rec *rec,
+	const void			*value,
+	int				valuelen)
+{
+	irec->p_ino = be64_to_cpu(rec->p_ino);
+	irec->p_gen = be32_to_cpu(rec->p_gen);
+	irec->p_diroffset = be32_to_cpu(rec->p_diroffset);
+
+	if (!value) {
+		irec->p_namelen = 0;
+		return;
+	}
+
+	ASSERT(valuelen > 0);
+	ASSERT(valuelen < MAXNAMELEN);
+
+	valuelen = min(valuelen, MAXNAMELEN);
+
+	irec->p_namelen = valuelen;
+	memcpy(irec->p_name, value, valuelen);
+	memset(&irec->p_name[valuelen], 0, sizeof(irec->p_name) - valuelen);
+}
+
 int
 __xfs_parent_init(
 	struct xfs_mount		*mp,
diff --git a/libxfs/xfs_parent.h b/libxfs/xfs_parent.h
index 4ffcb81d..f4f5887d 100644
--- a/libxfs/xfs_parent.h
+++ b/libxfs/xfs_parent.h
@@ -15,6 +15,25 @@ bool xfs_parent_namecheck(struct xfs_mount *mp,
 bool xfs_parent_valuecheck(struct xfs_mount *mp, const void *value,
 		size_t valuelen);
 
+/*
+ * Incore version of a parent pointer, also contains dirent name so callers
+ * can pass/obtain all the parent pointer information in a single structure
+ */
+struct xfs_parent_name_irec {
+	/* Key fields for looking up a particular parent pointer. */
+	xfs_ino_t		p_ino;
+	uint32_t		p_gen;
+	xfs_dir2_dataptr_t	p_diroffset;
+
+	/* Attributes of a parent pointer. */
+	uint8_t			p_namelen;
+	unsigned char		p_name[MAXNAMELEN];
+};
+
+void xfs_parent_irec_from_disk(struct xfs_parent_name_irec *irec,
+		const struct xfs_parent_name_rec *rec,
+		const void *value, int valuelen);
+
 /*
  * Dynamically allocd structure used to wrap the needed data to pass around
  * the defer ops machinery
@@ -32,8 +51,6 @@ struct xfs_parent_defer {
 void xfs_init_parent_name_rec(struct xfs_parent_name_rec *rec,
 			      struct xfs_inode *ip,
 			      uint32_t p_diroffset);
-void xfs_init_parent_ptr(struct xfs_parent_ptr *xpp,
-			 const struct xfs_parent_name_rec *rec);
 int __xfs_parent_init(struct xfs_mount *mp, bool grab_log,
 		struct xfs_parent_defer **parentp);