[RFC PATCH 1/3] libfs: rework dcache_readdir to use an internal function with callback

[James Bottomley <James.Bottomley@HansenPartnership.com>]

No functional change.  Preparatory to using the internal function to
iterate a directory with just a dentry not a file.

Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
---
 fs/libfs.c | 41 +++++++++++++++++++++++++++++------------
 1 file changed, 29 insertions(+), 12 deletions(-)

diff --git a/fs/libfs.c b/fs/libfs.c
index 8444f5cc4064..816bfe6c0430 100644
--- a/fs/libfs.c
+++ b/fs/libfs.c
@@ -189,28 +189,21 @@ EXPORT_SYMBOL(dcache_dir_lseek);
  * for ramfs-type trees they can't go away without unlink() or rmdir(),
  * both impossible due to the lock on directory.
  */
-
-int dcache_readdir(struct file *file, struct dir_context *ctx)
+static void internal_readdir(struct dentry *dentry, struct dentry *cursor,
+			     void *data, bool start,
+			     bool (*callback)(void *, struct dentry *))
 {
-	struct dentry *dentry = file->f_path.dentry;
-	struct dentry *cursor = file->private_data;
 	struct dentry *next = NULL;
 	struct hlist_node **p;
 
-	if (!dir_emit_dots(file, ctx))
-		return 0;
-
-	if (ctx->pos == 2)
+	if (start)
 		p = &dentry->d_children.first;
 	else
 		p = &cursor->d_sib.next;
 
 	while ((next = scan_positives(cursor, p, 1, next)) != NULL) {
-		if (!dir_emit(ctx, next->d_name.name, next->d_name.len,
-			      d_inode(next)->i_ino,
-			      fs_umode_to_dtype(d_inode(next)->i_mode)))
+		if (!callback(data, next))
 			break;
-		ctx->pos++;
 		p = &next->d_sib.next;
 	}
 	spin_lock(&dentry->d_lock);
@@ -219,6 +212,30 @@ int dcache_readdir(struct file *file, struct dir_context *ctx)
 		hlist_add_before(&cursor->d_sib, &next->d_sib);
 	spin_unlock(&dentry->d_lock);
 	dput(next);
+}
+
+static bool dcache_readdir_callback(void *data, struct dentry *entry)
+{
+	struct dir_context *ctx = data;
+
+	if (!dir_emit(ctx, entry->d_name.name, entry->d_name.len,
+		      d_inode(entry)->i_ino,
+		      fs_umode_to_dtype(d_inode(entry)->i_mode)))
+		return false;
+	ctx->pos++;
+	return true;
+}
+
+int dcache_readdir(struct file *file, struct dir_context *ctx)
+{
+	struct dentry *dentry = file->f_path.dentry;
+	struct dentry *cursor = file->private_data;
+
+	if (!dir_emit_dots(file, ctx))
+		return 0;
+
+	internal_readdir(dentry, cursor, ctx, ctx->pos == 2,
+			 dcache_readdir_callback);
 
 	return 0;
 }
-- 
2.43.0