libfuse: add readdirplus support in fuse_lowlevel_ops

This patch implements readdirplus support in FUSE usersapce. It adds
a new fuse lowlevel operations fuse_lowleve_ops::readdir_plus,
corespoding mount options and helper functions to maintain buffer.

[From: Eric Wong <normalperson@yhbt.net>]

This makes our terminology consistent with NFS and
our kernel module, as well as reducing user/developer
confusion in the command-line.

Note: I'm keeping "fuse_add_direntry_plus" since that is
less standardized in its use than "readdirplus" for now.

Signed-off-by: Feng Shuo <steve.shuo.feng@gmail.com>

3 files changed, 71 insertions, 1 deletions

diff --git a/include/fuse_common.h b/include/fuse_common.h
index 58458ab..c8a2409 100644
--- a/include/fuse_common.h
+++ b/include/fuse_common.h
@@ -112,6 +112,7 @@ struct fuse_file_info {
 #define FUSE_CAP_FLOCK_LOCKS		(1 << 10)
 #define FUSE_CAP_IOCTL_DIR		(1 << 11)
 #define FUSE_CAP_AUTO_INVAL_DATA 	(1 << 12)
+#define FUSE_CAP_READDIRPLUS		(1 << 13)
 
 /**
  * Ioctl flags
diff --git a/include/fuse_kernel.h b/include/fuse_kernel.h
index df8e9b9..28fefbb 100644
--- a/include/fuse_kernel.h
+++ b/include/fuse_kernel.h
@@ -86,6 +86,9 @@
  *
  * 7.20
  *  - add FUSE_AUTO_INVAL_DATA
+ *
+ * 7.21
+ *  - add FUSE_READDIRPLUS
  */
 
 #ifndef _LINUX_FUSE_H
@@ -126,7 +129,7 @@
 #define FUSE_KERNEL_VERSION 7
 
 /** Minor version number of this interface */
-#define FUSE_KERNEL_MINOR_VERSION 20
+#define FUSE_KERNEL_MINOR_VERSION 21
 
 /** The node ID of the root inode */
 #define FUSE_ROOT_ID 1
@@ -228,6 +231,7 @@ struct fuse_file_lock {
 #define FUSE_FLOCK_LOCKS	(1 << 10)
 #define FUSE_HAS_IOCTL_DIR	(1 << 11)
 #define FUSE_AUTO_INVAL_DATA	(1 << 12)
+#define FUSE_DO_READDIRPLUS	(1 << 13)
 
 /**
  * CUSE INIT request/reply flags
@@ -334,6 +338,7 @@ enum fuse_opcode {
 	FUSE_NOTIFY_REPLY  = 41,
 	FUSE_BATCH_FORGET  = 42,
 	FUSE_FALLOCATE     = 43,
+	FUSE_READDIRPLUS   = 44,
 
 	/* CUSE specific operations */
 	CUSE_INIT          = 4096,
@@ -665,6 +670,16 @@ struct fuse_dirent {
 #define FUSE_DIRENT_SIZE(d) \
 	FUSE_DIRENT_ALIGN(FUSE_NAME_OFFSET + (d)->namelen)
 
+struct fuse_direntplus {
+	struct fuse_entry_out entry_out;
+	struct fuse_dirent dirent;
+};
+
+#define FUSE_NAME_OFFSET_DIRENTPLUS \
+	offsetof(struct fuse_direntplus, dirent.name)
+#define FUSE_DIRENTPLUS_SIZE(d) \
+	FUSE_DIRENT_ALIGN(FUSE_NAME_OFFSET_DIRENTPLUS + (d)->dirent.namelen)
+
 struct fuse_notify_inval_inode_out {
 	__u64	ino;
 	__s64	off;
diff --git a/include/fuse_lowlevel.h b/include/fuse_lowlevel.h
index 9a24bcc..22c2e5a 100644
--- a/include/fuse_lowlevel.h
+++ b/include/fuse_lowlevel.h
@@ -1016,6 +1016,32 @@ struct fuse_lowlevel_ops {
 	 */
 	void (*fallocate) (fuse_req_t req, fuse_ino_t ino, int mode,
 		       off_t offset, off_t length, struct fuse_file_info *fi);
+
+	/**
+	 * Read directory with attributes
+	 *
+	 * Send a buffer filled using fuse_add_direntry_plus(), with size not
+	 * exceeding the requested size.  Send an empty buffer on end of
+	 * stream.
+	 *
+	 * fi->fh will contain the value set by the opendir method, or
+	 * will be undefined if the opendir method didn't set any value.
+	 *
+	 * Introduced in version 3.0
+	 *
+	 * Valid replies:
+	 *   fuse_reply_buf
+	 *   fuse_reply_data
+	 *   fuse_reply_err
+	 *
+	 * @param req request handle
+	 * @param ino the inode number
+	 * @param size maximum number of bytes to send
+	 * @param off offset to continue reading the directory stream
+	 * @param fi file information
+	 */
+	void (*readdirplus) (fuse_req_t req, fuse_ino_t ino, size_t size, off_t off,
+			 struct fuse_file_info *fi);
 };
 
 /**
@@ -1252,6 +1278,34 @@ size_t fuse_add_direntry(fuse_req_t req, char *buf, size_t bufsize,
 			 off_t off);
 
 /**
+ * Add a directory entry to the buffer with the attributes
+ *
+ * Buffer needs to be large enough to hold the entry.  If it's not,
+ * then the entry is not filled in but the size of the entry is still
+ * returned.  The caller can check this by comparing the bufsize
+ * parameter with the returned entry size.  If the entry size is
+ * larger than the buffer size, the operation failed.
+ *
+ * From the 'stbuf' argument the st_ino field and bits 12-15 of the
+ * st_mode field are used.  The other fields are ignored.
+ *
+ * Note: offsets do not necessarily represent physical offsets, and
+ * could be any marker, that enables the implementation to find a
+ * specific point in the directory stream.
+ *
+ * @param req request handle
+ * @param buf the point where the new entry will be added to the buffer
+ * @param bufsize remaining size of the buffer
+ * @param name the name of the entry
+ * @param e the directory entry
+ * @param off the offset of the next entry
+ * @return the space needed for the entry
+ */
+size_t fuse_add_direntry_plus(fuse_req_t req, char *buf, size_t bufsize,
+			      const char *name,
+			      const struct fuse_entry_param *e, off_t off);
+
+/**
  * Reply to ask for data fetch and output buffer preparation.  ioctl
  * will be retried with the specified input data fetched and output
  * buffer prepared.