[PATCH] fuse: transfer readdir data through device

This patch removes a long lasting "hack" in FUSE, which used a separate
channel (a file descriptor refering to a disk-file) to transfer directory
contents from userspace to the kernel.

The patch adds three new operations (OPENDIR, READDIR, RELEASEDIR), which
have semantics and implementation exactly maching the respective file
operations (OPEN, READ, RELEASE).

This simplifies the directory reading code.  Also disk space is not
necessary, which can be important in embedded systems.

Signed-off-by: Miklos Szeredi <miklos@szeredi.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 28 insertions, 10 deletions

diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index 6bc3fb26de39..224453557cf6 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -12,7 +12,7 @@
 #include <linux/slab.h>
 #include <linux/kernel.h>
 
-static int fuse_open(struct inode *inode, struct file *file)
+int fuse_open_common(struct inode *inode, struct file *file, int isdir)
 {
 	struct fuse_conn *fc = get_fuse_conn(inode);
 	struct fuse_req *req;
@@ -56,7 +56,7 @@ static int fuse_open(struct inode *inode, struct file *file)
 
 	memset(&inarg, 0, sizeof(inarg));
 	inarg.flags = file->f_flags & ~(O_CREAT | O_EXCL | O_NOCTTY | O_TRUNC);
-	req->in.h.opcode = FUSE_OPEN;
+	req->in.h.opcode = isdir ? FUSE_OPENDIR : FUSE_OPEN;
 	req->in.h.nodeid = get_node_id(inode);
 	req->inode = inode;
 	req->in.numargs = 1;
@@ -85,7 +85,7 @@ static int fuse_open(struct inode *inode, struct file *file)
 	return err;
 }
 
-static int fuse_release(struct inode *inode, struct file *file)
+int fuse_release_common(struct inode *inode, struct file *file, int isdir)
 {
 	struct fuse_conn *fc = get_fuse_conn(inode);
 	struct fuse_file *ff = file->private_data;
@@ -94,7 +94,7 @@ static int fuse_release(struct inode *inode, struct file *file)
 
 	inarg->fh = ff->fh;
 	inarg->flags = file->f_flags & ~O_EXCL;
-	req->in.h.opcode = FUSE_RELEASE;
+	req->in.h.opcode = isdir ? FUSE_RELEASEDIR : FUSE_RELEASE;
 	req->in.h.nodeid = get_node_id(inode);
 	req->inode = inode;
 	req->in.numargs = 1;
@@ -107,6 +107,16 @@ static int fuse_release(struct inode *inode, struct file *file)
 	return 0;
 }
 
+static int fuse_open(struct inode *inode, struct file *file)
+{
+	return fuse_open_common(inode, file, 0);
+}
+
+static int fuse_release(struct inode *inode, struct file *file)
+{
+	return fuse_release_common(inode, file, 0);
+}
+
 static int fuse_flush(struct file *file)
 {
 	struct inode *inode = file->f_dentry->d_inode;
@@ -178,8 +188,9 @@ static int fuse_fsync(struct file *file, struct dentry *de, int datasync)
 	return err;
 }
 
-static ssize_t fuse_send_read(struct fuse_req *req, struct file *file,
-			      struct inode *inode, loff_t pos,  size_t count)
+size_t fuse_send_read_common(struct fuse_req *req, struct file *file,
+			     struct inode *inode, loff_t pos, size_t count,
+			     int isdir)
 {
 	struct fuse_conn *fc = get_fuse_conn(inode);
 	struct fuse_file *ff = file->private_data;
@@ -189,7 +200,7 @@ static ssize_t fuse_send_read(struct fuse_req *req, struct file *file,
 	inarg.fh = ff->fh;
 	inarg.offset = pos;
 	inarg.size = count;
-	req->in.h.opcode = FUSE_READ;
+	req->in.h.opcode = isdir ? FUSE_READDIR : FUSE_READ;
 	req->in.h.nodeid = get_node_id(inode);
 	req->inode = inode;
 	req->file = file;
@@ -204,6 +215,13 @@ static ssize_t fuse_send_read(struct fuse_req *req, struct file *file,
 	return req->out.args[0].size;
 }
 
+static inline size_t fuse_send_read(struct fuse_req *req, struct file *file,
+				    struct inode *inode, loff_t pos,
+				    size_t count)
+{
+	return fuse_send_read_common(req, file, inode, pos, count, 0);
+}
+
 static int fuse_readpage(struct file *file, struct page *page)
 {
 	struct inode *inode = page->mapping->host;
@@ -293,8 +311,8 @@ static int fuse_readpages(struct file *file, struct address_space *mapping,
 	return err;
 }
 
-static ssize_t fuse_send_write(struct fuse_req *req, struct file *file,
-			       struct inode *inode, loff_t pos, size_t count)
+static size_t fuse_send_write(struct fuse_req *req, struct file *file,
+			      struct inode *inode, loff_t pos, size_t count)
 {
 	struct fuse_conn *fc = get_fuse_conn(inode);
 	struct fuse_file *ff = file->private_data;
@@ -332,7 +350,7 @@ static int fuse_commit_write(struct file *file, struct page *page,
 			     unsigned offset, unsigned to)
 {
 	int err;
-	ssize_t nres;
+	size_t nres;
 	unsigned count = to - offset;
 	struct inode *inode = page->mapping->host;
 	struct fuse_conn *fc = get_fuse_conn(inode);