[PATCH 19/32] xfs: enable creation of dynamically allocated metadir path structures

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

From: Darrick J. Wong <djwong@xxxxxxxxxx>

Add a few helper functions so that it's possible to allocate
xfs_imeta_path objects dynamically, along with dynamically allocated
path components.  Eventually we're going to want to support paths of the
form "/realtime/$rtgroup.rmap", and this is necessary for that.

Signed-off-by: Darrick J. Wong <djwong@xxxxxxxxxx>
---
 fs/xfs/libxfs/xfs_imeta.c |   46 +++++++++++++++++++++++++++++++++++++++++++++
 fs/xfs/libxfs/xfs_imeta.h |   15 +++++++++++++++
 2 files changed, 61 insertions(+)


diff --git a/fs/xfs/libxfs/xfs_imeta.c b/fs/xfs/libxfs/xfs_imeta.c
index e3651c7bba2b3..10249a1c36c73 100644
--- a/fs/xfs/libxfs/xfs_imeta.c
+++ b/fs/xfs/libxfs/xfs_imeta.c
@@ -1015,3 +1015,49 @@ xfs_imeta_mount(
 
 	return 0;
 }
+
+/* Create a path to a file within the metadata directory tree. */
+int
+xfs_imeta_create_file_path(
+	struct xfs_mount	*mp,
+	unsigned int		nr_components,
+	struct xfs_imeta_path	**pathp)
+{
+	struct xfs_imeta_path	*p;
+	unsigned char		**components;
+
+	p = kzalloc(sizeof(struct xfs_imeta_path), GFP_KERNEL);
+	if (!p)
+		return -ENOMEM;
+
+	components = kvcalloc(nr_components, sizeof(unsigned char *),
+			GFP_KERNEL);
+	if (!components) {
+		kfree(p);
+		return -ENOMEM;
+	}
+
+	p->im_depth = nr_components;
+	p->im_path = (const unsigned char **)components;
+	p->im_ftype = XFS_DIR3_FT_REG_FILE;
+	*pathp = p;
+	return 0;
+}
+
+/* Free a metadata directory tree path. */
+void
+xfs_imeta_free_path(
+	const struct xfs_imeta_path	*path)
+{
+	unsigned int			i;
+
+	if (path->im_flags & XFS_IMETA_PATH_STATIC)
+		return;
+
+	for (i = 0; i < path->im_depth; i++) {
+		if ((path->im_dynamicmask & (1ULL << i)) && path->im_path[i])
+			kfree(path->im_path[i]);
+	}
+	kfree(path->im_path);
+	kfree(path);
+}
diff --git a/fs/xfs/libxfs/xfs_imeta.h b/fs/xfs/libxfs/xfs_imeta.h
index b8e360bbdfbe1..3b5953efc013c 100644
--- a/fs/xfs/libxfs/xfs_imeta.h
+++ b/fs/xfs/libxfs/xfs_imeta.h
@@ -15,6 +15,8 @@ const struct xfs_imeta_path name = { \
 	.im_path = (path), \
 	.im_ftype = XFS_DIR3_FT_REG_FILE, \
 	.im_depth = ARRAY_SIZE(path), \
+	.im_flags = XFS_IMETA_PATH_STATIC, \
+	.im_dynamicmask = 0, \
 }
 
 /* Key for looking up metadata inodes. */
@@ -22,6 +24,12 @@ struct xfs_imeta_path {
 	/* Array of string pointers. */
 	const unsigned char	**im_path;
 
+	/* Each bit corresponds to an element of im_path needing to be freed */
+	unsigned long long	im_dynamicmask;
+
+	/* XFS_IMETA_* path flags */
+	uint16_t		im_flags;
+
 	/* Number of strings in path. */
 	uint8_t			im_depth;
 
@@ -29,6 +37,9 @@ struct xfs_imeta_path {
 	uint8_t			im_ftype;
 };
 
+/* Path is statically allocated. */
+#define XFS_IMETA_PATH_STATIC	(1U << 0)
+
 /* Cleanup widget for metadata inode creation and deletion. */
 struct xfs_imeta_update {
 	struct xfs_mount	*mp;
@@ -72,6 +83,10 @@ int xfs_imeta_lookup(struct xfs_trans *tp, const struct xfs_imeta_path *path,
 int xfs_imeta_dir_parent(struct xfs_trans *tp,
 		const struct xfs_imeta_path *path, struct xfs_inode **dpp);
 
+int xfs_imeta_create_file_path(struct xfs_mount *mp,
+		unsigned int nr_components, struct xfs_imeta_path **pathp);
+void xfs_imeta_free_path(const struct xfs_imeta_path *path);
+
 void xfs_imeta_set_iflag(struct xfs_trans *tp, struct xfs_inode *ip);
 void xfs_imeta_clear_iflag(struct xfs_trans *tp, struct xfs_inode *ip);