fuse: use req->page_descs[] for argpages cases

Previously, anyone who set flag 'argpages' only filled req->pages[] and set
per-request page_offset. This patch re-works all cases where argpages=1 to
fill req->page_descs[] properly.

Having req->page_descs[] filled properly allows to re-work fuse_copy_pages()
to copy page fragments described by req->page_descs[]. This will be useful
for next patches optimizing direct_IO.

Signed-off-by: Maxim Patlasov <mpatlasov@parallels.com>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>

fs/fuse/cuse.c

@@ -449,6 +449,7 @@ static int cuse_send_init(struct cuse_conn *cc)
 	req->out.argvar = 1;
 	req->out.argpages = 1;
 	req->pages[0] = page;
+	req->page_descs[0].length = req->out.args[1].size;
 	req->num_pages = 1;
 	req->end = cuse_process_init_reply;
 	fuse_request_send_background(fc, req);

fs/fuse/dev.c

@@ -903,11 +903,11 @@ static int fuse_copy_pages(struct fuse_copy_state *cs, unsigned nbytes,
 {
 	unsigned i;
 	struct fuse_req *req = cs->req;
-	unsigned offset = req->page_descs[0].offset;
-	unsigned count = min(nbytes, (unsigned) PAGE_SIZE - offset);
 
 	for (i = 0; i < req->num_pages && (nbytes || zeroing); i++) {
 		int err;
+		unsigned offset = req->page_descs[i].offset;
+		unsigned count = min(nbytes, req->page_descs[i].length);
 
 		err = fuse_copy_page(cs, &req->pages[i], offset, count,
 				     zeroing);
@@ -915,8 +915,6 @@ static int fuse_copy_pages(struct fuse_copy_state *cs, unsigned nbytes,
 			return err;
 
 		nbytes -= count;
-		count = min(nbytes, (unsigned) PAGE_SIZE);
-		offset = 0;
 	}
 	return 0;
 }
@@ -1626,6 +1624,7 @@ static int fuse_retrieve(struct fuse_conn *fc, struct inode *inode,
 
 		this_num = min_t(unsigned, num, PAGE_CACHE_SIZE - offset);
 		req->pages[req->num_pages] = page;
+		req->page_descs[req->num_pages].length = this_num;
 		req->num_pages++;
 
 		offset = 0;

fs/fuse/dir.c

@@ -1317,6 +1317,7 @@ static int fuse_readdir(struct file *file, void *dstbuf, filldir_t filldir)
 	req->out.argpages = 1;
 	req->num_pages = 1;
 	req->pages[0] = page;
+	req->page_descs[0].length = PAGE_SIZE;
 	if (fc->do_readdirplus) {
 		attr_version = fuse_get_attr_version(fc);
 		fuse_read_fill(req, file, file->f_pos, PAGE_SIZE,

fs/fuse/file.c

@@ -555,6 +555,7 @@ static int fuse_readpage(struct file *file, struct page *page)
 	req->out.argpages = 1;
 	req->num_pages = 1;
 	req->pages[0] = page;
+	req->page_descs[0].length = count;
 	num_read = fuse_send_read(req, file, pos, count, NULL);
 	err = req->out.h.error;
 	fuse_put_request(fc, req);
@@ -674,6 +675,7 @@ static int fuse_readpages_fill(void *_data, struct page *page)
 
 	page_cache_get(page);
 	req->pages[req->num_pages] = page;
+	req->page_descs[req->num_pages].length = PAGE_SIZE;
 	req->num_pages++;
 	data->nr_pages--;
 	return 0;
@@ -869,6 +871,7 @@ static ssize_t fuse_fill_write_pages(struct fuse_req *req,
 
 		err = 0;
 		req->pages[req->num_pages] = page;
+		req->page_descs[req->num_pages].length = tmp;
 		req->num_pages++;
 
 		iov_iter_advance(ii, tmp);
@@ -1044,6 +1047,15 @@ static void fuse_release_user_pages(struct fuse_req *req, int write)
 	}
 }
 
+static inline void fuse_page_descs_length_init(struct fuse_req *req)
+{
+	int i;
+
+	for (i = 0; i < req->num_pages; i++)
+		req->page_descs[i].length = PAGE_SIZE -
+			req->page_descs[i].offset;
+}
+
 static int fuse_get_user_pages(struct fuse_req *req, const char __user *buf,
 			       size_t *nbytesp, int write)
 {
@@ -1071,6 +1083,7 @@ static int fuse_get_user_pages(struct fuse_req *req, const char __user *buf,
 
 	req->num_pages = npages;
 	req->page_descs[0].offset = offset;
+	fuse_page_descs_length_init(req);
 
 	if (write)
 		req->in.argpages = 1;
@@ -1078,6 +1091,11 @@ static int fuse_get_user_pages(struct fuse_req *req, const char __user *buf,
 		req->out.argpages = 1;
 
 	nbytes = (req->num_pages << PAGE_SHIFT) - req->page_descs[0].offset;
+
+	if (*nbytesp < nbytes)
+		req->page_descs[req->num_pages - 1].length -=
+			nbytes - *nbytesp;
+
 	*nbytesp = min(*nbytesp, nbytes);
 
 	return 0;
@@ -1315,6 +1333,7 @@ static int fuse_writepage_locked(struct page *page)
 	req->num_pages = 1;
 	req->pages[0] = tmp_page;
 	req->page_descs[0].offset = 0;
+	req->page_descs[0].length = PAGE_SIZE;
 	req->end = fuse_writepage_end;
 	req->inode = inode;
 
@@ -1902,6 +1921,7 @@ long fuse_do_ioctl(struct file *file, unsigned int cmd, unsigned long arg,
 	}
 	memcpy(req->pages, pages, sizeof(req->pages[0]) * num_pages);
 	req->num_pages = num_pages;
+	fuse_page_descs_length_init(req);
 
 	/* okay, let's send it to the client */
 	req->in.h.opcode = FUSE_IOCTL;