[PATCH 11/13] fuse: Add support to copy from/to the ring buffer

[Bernd Schubert <bschubert@ddn.com>]

This adds support to existing fuse copy code to copy
from/to the ring buffer. The ring buffer is here mmaped
shared between kernel and userspace.

This also fuse_ prefixes the copy_out_args function

Signed-off-by: Bernd Schubert <bschubert@ddn.com>
cc: Miklos Szeredi <miklos@szeredi.hu>
cc: linux-fsdevel@vger.kernel.org
cc: Amir Goldstein <amir73il@gmail.com>
cc: fuse-devel@lists.sourceforge.net
---
 fs/fuse/dev.c        | 60 ++++++++++++++++++++++++++------------------
 fs/fuse/fuse_dev_i.h | 35 ++++++++++++++++++++++++++
 2 files changed, 70 insertions(+), 25 deletions(-)

diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
index 4e79cdba540c..de9193f66c8b 100644
--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -628,21 +628,7 @@ static int unlock_request(struct fuse_req *req)
 	return err;
 }
 
-struct fuse_copy_state {
-	int write;
-	struct fuse_req *req;
-	struct iov_iter *iter;
-	struct pipe_buffer *pipebufs;
-	struct pipe_buffer *currbuf;
-	struct pipe_inode_info *pipe;
-	unsigned long nr_segs;
-	struct page *pg;
-	unsigned len;
-	unsigned offset;
-	unsigned move_pages:1;
-};
-
-static void fuse_copy_init(struct fuse_copy_state *cs, int write,
+void fuse_copy_init(struct fuse_copy_state *cs, int write,
 			   struct iov_iter *iter)
 {
 	memset(cs, 0, sizeof(*cs));
@@ -653,6 +639,7 @@ static void fuse_copy_init(struct fuse_copy_state *cs, int write,
 /* Unmap and put previous page of userspace buffer */
 static void fuse_copy_finish(struct fuse_copy_state *cs)
 {
+
 	if (cs->currbuf) {
 		struct pipe_buffer *buf = cs->currbuf;
 
@@ -717,6 +704,10 @@ static int fuse_copy_fill(struct fuse_copy_state *cs)
 			cs->pipebufs++;
 			cs->nr_segs++;
 		}
+	} else if (cs->is_uring) {
+		if (cs->ring.offset > cs->ring.buf_sz)
+			return -ERANGE;
+		cs->len = cs->ring.buf_sz - cs->ring.offset;
 	} else {
 		size_t off;
 		err = iov_iter_get_pages2(cs->iter, &page, PAGE_SIZE, 1, &off);
@@ -735,21 +726,35 @@ static int fuse_copy_fill(struct fuse_copy_state *cs)
 static int fuse_copy_do(struct fuse_copy_state *cs, void **val, unsigned *size)
 {
 	unsigned ncpy = min(*size, cs->len);
+
 	if (val) {
-		void *pgaddr = kmap_local_page(cs->pg);
-		void *buf = pgaddr + cs->offset;
+
+		void *pgaddr;
+		void *buf;
+
+		if (cs->is_uring) {
+			buf = cs->ring.buf + cs->ring.offset;
+			cs->ring.offset += ncpy;
+
+		} else {
+			pgaddr = kmap_local_page(cs->pg);
+			buf = pgaddr + cs->offset;
+		}
 
 		if (cs->write)
 			memcpy(buf, *val, ncpy);
 		else
 			memcpy(*val, buf, ncpy);
 
-		kunmap_local(pgaddr);
+		if (pgaddr)
+			kunmap_local(pgaddr);
+
 		*val += ncpy;
 	}
 	*size -= ncpy;
 	cs->len -= ncpy;
 	cs->offset += ncpy;
+
 	return ncpy;
 }
 
@@ -997,9 +1002,9 @@ static int fuse_copy_one(struct fuse_copy_state *cs, void *val, unsigned size)
 }
 
 /* Copy request arguments to/from userspace buffer */
-static int fuse_copy_args(struct fuse_copy_state *cs, unsigned numargs,
-			  unsigned argpages, struct fuse_arg *args,
-			  int zeroing)
+int fuse_copy_args(struct fuse_copy_state *cs, unsigned int numargs,
+		   unsigned int argpages, struct fuse_arg *args,
+		   int zeroing)
 {
 	int err = 0;
 	unsigned i;
@@ -1806,10 +1811,15 @@ static struct fuse_req *request_find(struct fuse_pqueue *fpq, u64 unique)
 	return NULL;
 }
 
-static int copy_out_args(struct fuse_copy_state *cs, struct fuse_args *args,
-			 unsigned nbytes)
+int fuse_copy_out_args(struct fuse_copy_state *cs, struct fuse_args *args,
+		       unsigned int nbytes)
 {
-	unsigned reqsize = sizeof(struct fuse_out_header);
+
+	unsigned int reqsize = 0;
+
+	/* Uring has the out header outside of args */
+	if (!cs->is_uring)
+		reqsize = sizeof(struct fuse_out_header);
 
 	reqsize += fuse_len_args(args->out_numargs, args->out_args);
 
@@ -1909,7 +1919,7 @@ static ssize_t fuse_dev_do_write(struct fuse_dev *fud,
 	if (oh.error)
 		err = nbytes != sizeof(oh) ? -EINVAL : 0;
 	else
-		err = copy_out_args(cs, req->args, nbytes);
+		err = fuse_copy_out_args(cs, req->args, nbytes);
 	fuse_copy_finish(cs);
 
 	spin_lock(&fpq->lock);
diff --git a/fs/fuse/fuse_dev_i.h b/fs/fuse/fuse_dev_i.h
index aea1f3f7aa5d..ccd128f81628 100644
--- a/fs/fuse/fuse_dev_i.h
+++ b/fs/fuse/fuse_dev_i.h
@@ -11,6 +11,33 @@
 #define FUSE_INT_REQ_BIT (1ULL << 0)
 #define FUSE_REQ_ID_STEP (1ULL << 1)
 
+struct fuse_copy_state {
+	int write;
+	struct fuse_req *req;
+	struct iov_iter *iter;
+	struct pipe_buffer *pipebufs;
+	struct pipe_buffer *currbuf;
+	struct pipe_inode_info *pipe;
+	unsigned long nr_segs;
+	struct page *pg;
+	unsigned int len;
+	unsigned int offset;
+	unsigned int move_pages:1, is_uring:1;
+	struct {
+		/* pointer into the ring buffer */
+		char *buf;
+
+		/* for copy to the ring request buffer, the buffer size - must
+		 * not be exceeded, for copy from the ring request buffer,
+		 * the size filled in by user space
+		 */
+		unsigned int buf_sz;
+
+		/* offset within buf while it is copying from/to the buf */
+		unsigned int offset;
+	} ring;
+};
+
 static inline struct fuse_dev *fuse_get_dev(struct file *file)
 {
 	/*
@@ -22,6 +49,14 @@ static inline struct fuse_dev *fuse_get_dev(struct file *file)
 
 void fuse_dev_end_requests(struct list_head *head);
 
+void fuse_copy_init(struct fuse_copy_state *cs, int write,
+			   struct iov_iter *iter);
+int fuse_copy_args(struct fuse_copy_state *cs, unsigned int numargs,
+		   unsigned int argpages, struct fuse_arg *args,
+		   int zeroing);
+int fuse_copy_out_args(struct fuse_copy_state *cs, struct fuse_args *args,
+		       unsigned int nbytes);
+
 #endif
 
 
-- 
2.37.2