CIFS: Separate page processing from writepages

Signed-off-by: Pavel Shilovsky <pshilovsky@samba.org>
Reviewed-by: Jeff Layton <jlayton@samba.org>
Signed-off-by: Steve French <smfrench@gmail.com>

fs/cifs/file.c

@@ -1878,73 +1878,15 @@ static int cifs_partialpagewrite(struct page *page, unsigned from, unsigned to)
 	return rc;
 }
 
-static int cifs_writepages(struct address_space *mapping,
-			   struct writeback_control *wbc)
+static unsigned int
+wdata_prepare_pages(struct cifs_writedata *wdata, unsigned int found_pages,
+		    struct address_space *mapping,
+		    struct writeback_control *wbc,
+		    pgoff_t end, pgoff_t *index, pgoff_t *next, bool *done)
 {
-	struct cifs_sb_info *cifs_sb = CIFS_SB(mapping->host->i_sb);
-	bool done = false, scanned = false, range_whole = false;
-	pgoff_t end, index;
-	struct cifs_writedata *wdata;
-	struct TCP_Server_Info *server;
+	unsigned int nr_pages = 0, i;
 	struct page *page;
-	int rc = 0;
-
-	/*
-	 * If wsize is smaller than the page cache size, default to writing
-	 * one page at a time via cifs_writepage
-	 */
-	if (cifs_sb->wsize < PAGE_CACHE_SIZE)
-		return generic_writepages(mapping, wbc);
-
-	if (wbc->range_cyclic) {
-		index = mapping->writeback_index; /* Start from prev offset */
-		end = -1;
-	} else {
-		index = wbc->range_start >> PAGE_CACHE_SHIFT;
-		end = wbc->range_end >> PAGE_CACHE_SHIFT;
-		if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX)
-			range_whole = true;
-		scanned = true;
-	}
-retry:
-	while (!done && index <= end) {
-		unsigned int i, nr_pages, found_pages;
-		pgoff_t next = 0, tofind;
-		struct page **pages;
-
-		tofind = min((cifs_sb->wsize / PAGE_CACHE_SIZE) - 1,
-				end - index) + 1;
 
-		wdata = cifs_writedata_alloc((unsigned int)tofind,
-					     cifs_writev_complete);
-		if (!wdata) {
-			rc = -ENOMEM;
-			break;
-		}
-
-		/*
-		 * find_get_pages_tag seems to return a max of 256 on each
-		 * iteration, so we must call it several times in order to
-		 * fill the array or the wsize is effectively limited to
-		 * 256 * PAGE_CACHE_SIZE.
-		 */
-		found_pages = 0;
-		pages = wdata->pages;
-		do {
-			nr_pages = find_get_pages_tag(mapping, &index,
-							PAGECACHE_TAG_DIRTY,
-							tofind, pages);
-			found_pages += nr_pages;
-			tofind -= nr_pages;
-			pages += nr_pages;
-		} while (nr_pages && tofind && index <= end);
-
-		if (found_pages == 0) {
-			kref_put(&wdata->refcount, cifs_writedata_release);
-			break;
-		}
-
-		nr_pages = 0;
 	for (i = 0; i < found_pages; i++) {
 		page = wdata->pages[i];
 		/*
@@ -1966,12 +1908,12 @@ static int cifs_writepages(struct address_space *mapping,
 		}
 
 		if (!wbc->range_cyclic && page->index > end) {
-				done = true;
+			*done = true;
 			unlock_page(page);
 			break;
 		}
 
-			if (next && (page->index != next)) {
+		if (*next && (page->index != *next)) {
 			/* Not next consecutive page */
 			unlock_page(page);
 			break;
@@ -1991,22 +1933,21 @@ static int cifs_writepages(struct address_space *mapping,
 		 * See cifs_writepage() for more commentary.
 		 */
 		set_page_writeback(page);
-
 		if (page_offset(page) >= i_size_read(mapping->host)) {
-				done = true;
+			*done = true;
 			unlock_page(page);
 			end_page_writeback(page);
 			break;
 		}
 
 		wdata->pages[i] = page;
-			next = page->index + 1;
+		*next = page->index + 1;
 		++nr_pages;
 	}
 
 	/* reset index to refind any pages skipped */
 	if (nr_pages == 0)
-			index = wdata->pages[0]->index + 1;
+		*index = wdata->pages[0]->index + 1;
 
 	/* put any pages we aren't going to use */
 	for (i = nr_pages; i < found_pages; i++) {
@@ -2014,6 +1955,77 @@ static int cifs_writepages(struct address_space *mapping,
 		wdata->pages[i] = NULL;
 	}
 
+	return nr_pages;
+}
+
+static int cifs_writepages(struct address_space *mapping,
+			   struct writeback_control *wbc)
+{
+	struct cifs_sb_info *cifs_sb = CIFS_SB(mapping->host->i_sb);
+	bool done = false, scanned = false, range_whole = false;
+	pgoff_t end, index;
+	struct cifs_writedata *wdata;
+	struct TCP_Server_Info *server;
+	int rc = 0;
+
+	/*
+	 * If wsize is smaller than the page cache size, default to writing
+	 * one page at a time via cifs_writepage
+	 */
+	if (cifs_sb->wsize < PAGE_CACHE_SIZE)
+		return generic_writepages(mapping, wbc);
+
+	if (wbc->range_cyclic) {
+		index = mapping->writeback_index; /* Start from prev offset */
+		end = -1;
+	} else {
+		index = wbc->range_start >> PAGE_CACHE_SHIFT;
+		end = wbc->range_end >> PAGE_CACHE_SHIFT;
+		if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX)
+			range_whole = true;
+		scanned = true;
+	}
+retry:
+	while (!done && index <= end) {
+		unsigned int i, nr_pages, found_pages;
+		pgoff_t next = 0, tofind;
+		struct page **pages;
+
+		tofind = min((cifs_sb->wsize / PAGE_CACHE_SIZE) - 1,
+				end - index) + 1;
+
+		wdata = cifs_writedata_alloc((unsigned int)tofind,
+					     cifs_writev_complete);
+		if (!wdata) {
+			rc = -ENOMEM;
+			break;
+		}
+
+		/*
+		 * find_get_pages_tag seems to return a max of 256 on each
+		 * iteration, so we must call it several times in order to
+		 * fill the array or the wsize is effectively limited to
+		 * 256 * PAGE_CACHE_SIZE.
+		 */
+		found_pages = 0;
+		pages = wdata->pages;
+		do {
+			nr_pages = find_get_pages_tag(mapping, &index,
+							PAGECACHE_TAG_DIRTY,
+							tofind, pages);
+			found_pages += nr_pages;
+			tofind -= nr_pages;
+			pages += nr_pages;
+		} while (nr_pages && tofind && index <= end);
+
+		if (found_pages == 0) {
+			kref_put(&wdata->refcount, cifs_writedata_release);
+			break;
+		}
+
+		nr_pages = wdata_prepare_pages(wdata, found_pages, mapping, wbc,
+					       end, &index, &next, &done);
+
 		/* nothing to write? */
 		if (nr_pages == 0) {
 			kref_put(&wdata->refcount, cifs_writedata_release);