CIFS: Separate filling pages from iovec write

Reviewed-by: Shirish Pargaonkar <spargaonkar@suse.com>
Signed-off-by: Pavel Shilovsky <pshilovsky@samba.org>
Signed-off-by: Steve French <smfrench@gmail.com>

fs/cifs/file.c

@@ -2423,11 +2423,53 @@ cifs_uncached_retry_writev(struct cifs_writedata *wdata)
 	return rc;
 }
 
+static int
+wdata_fill_from_iovec(struct cifs_writedata *wdata, struct iov_iter *from,
+		      size_t *len, unsigned long *num_pages)
+{
+	size_t save_len, copied, bytes, cur_len = *len;
+	unsigned long i, nr_pages = *num_pages;
+
+	save_len = cur_len;
+	for (i = 0; i < nr_pages; i++) {
+		bytes = min_t(const size_t, cur_len, PAGE_SIZE);
+		copied = copy_page_from_iter(wdata->pages[i], 0, bytes, from);
+		cur_len -= copied;
+		/*
+		 * If we didn't copy as much as we expected, then that
+		 * may mean we trod into an unmapped area. Stop copying
+		 * at that point. On the next pass through the big
+		 * loop, we'll likely end up getting a zero-length
+		 * write and bailing out of it.
+		 */
+		if (copied < bytes)
+			break;
+	}
+	cur_len = save_len - cur_len;
+	*len = cur_len;
+
+	/*
+	 * If we have no data to send, then that probably means that
+	 * the copy above failed altogether. That's most likely because
+	 * the address in the iovec was bogus. Return -EFAULT and let
+	 * the caller free anything we allocated and bail out.
+	 */
+	if (!cur_len)
+		return -EFAULT;
+
+	/*
+	 * i + 1 now represents the number of pages we actually used in
+	 * the copy phase above.
+	 */
+	*num_pages = i + 1;
+	return 0;
+}
+
 static ssize_t
 cifs_iovec_write(struct file *file, struct iov_iter *from, loff_t *poffset)
 {
-	unsigned long nr_pages, i;
+	unsigned long nr_pages, num_pages, i;
-	size_t bytes, copied, len, cur_len;
+	size_t len, cur_len;
 	ssize_t total_written = 0;
 	loff_t offset;
 	struct cifsFileInfo *open_file;
@@ -2464,8 +2506,6 @@ cifs_iovec_write(struct file *file, struct iov_iter *from, loff_t *poffset)
 		pid = current->tgid;
 
 	do {
-		size_t save_len;
-
 		nr_pages = get_numpages(cifs_sb->wsize, len, &cur_len);
 		wdata = cifs_writedata_alloc(nr_pages,
 					     cifs_uncached_writev_complete);
@@ -2480,44 +2520,20 @@ cifs_iovec_write(struct file *file, struct iov_iter *from, loff_t *poffset)
 			break;
 		}
 
-		save_len = cur_len;
+		num_pages = nr_pages;
-		for (i = 0; i < nr_pages; i++) {
+		rc = wdata_fill_from_iovec(wdata, from, &cur_len, &num_pages);
-			bytes = min_t(size_t, cur_len, PAGE_SIZE);
+		if (rc) {
-			copied = copy_page_from_iter(wdata->pages[i], 0, bytes,
-						     from);
-			cur_len -= copied;
-			/*
-			 * If we didn't copy as much as we expected, then that
-			 * may mean we trod into an unmapped area. Stop copying
-			 * at that point. On the next pass through the big
-			 * loop, we'll likely end up getting a zero-length
-			 * write and bailing out of it.
-			 */
-			if (copied < bytes)
-				break;
-		}
-		cur_len = save_len - cur_len;
-
-		/*
-		 * If we have no data to send, then that probably means that
-		 * the copy above failed altogether. That's most likely because
-		 * the address in the iovec was bogus. Set the rc to -EFAULT,
-		 * free anything we allocated and bail out.
-		 */
-		if (!cur_len) {
 			for (i = 0; i < nr_pages; i++)
 				put_page(wdata->pages[i]);
 			kfree(wdata);
-			rc = -EFAULT;
 			break;
 		}
 
 		/*
-		 * i + 1 now represents the number of pages we actually used in
+		 * Bring nr_pages down to the number of pages we actually used,
-		 * the copy phase above. Bring nr_pages down to that, and free
+		 * and free any pages that we didn't use.
-		 * any pages that we didn't use.
 		 */
-		for ( ; nr_pages > i + 1; nr_pages--)
+		for ( ; nr_pages > num_pages; nr_pages--)
 			put_page(wdata->pages[nr_pages - 1]);
 
 		wdata->sync_mode = WB_SYNC_ALL;