cifs: abstract out function to marshal the iovec for readv receives

Cached and uncached reads will need to do different things here to
handle the difference when the pages are in pagecache and not. Abstract
out the function that marshals the page list into a kvec array.

Signed-off-by: Jeff Layton <jlayton@redhat.com>

1 files changed, 68 insertions, 0 deletions

diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index d210288e4a47..183381d9c4c1 100644
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -2654,6 +2654,73 @@ cifs_readv_complete(struct work_struct *work)
 	cifs_readdata_free(rdata);
 }
 
+static int
+cifs_readpages_marshal_iov(struct cifs_readdata *rdata, unsigned int remaining)
+{
+	int len = 0;
+	struct page *page, *tpage;
+	u64 eof;
+	pgoff_t eof_index;
+
+	/* determine the eof that the server (probably) has */
+	eof = CIFS_I(rdata->mapping->host)->server_eof;
+	eof_index = eof ? (eof - 1) >> PAGE_CACHE_SHIFT : 0;
+	cFYI(1, "eof=%llu eof_index=%lu", eof, eof_index);
+
+	rdata->nr_iov = 1;
+	list_for_each_entry_safe(page, tpage, &rdata->pages, lru) {
+		if (remaining >= PAGE_CACHE_SIZE) {
+			/* enough data to fill the page */
+			rdata->iov[rdata->nr_iov].iov_base = kmap(page);
+			rdata->iov[rdata->nr_iov].iov_len = PAGE_CACHE_SIZE;
+			cFYI(1, "%u: idx=%lu iov_base=%p iov_len=%zu",
+				rdata->nr_iov, page->index,
+				rdata->iov[rdata->nr_iov].iov_base,
+				rdata->iov[rdata->nr_iov].iov_len);
+			++rdata->nr_iov;
+			len += PAGE_CACHE_SIZE;
+			remaining -= PAGE_CACHE_SIZE;
+		} else if (remaining > 0) {
+			/* enough for partial page, fill and zero the rest */
+			rdata->iov[rdata->nr_iov].iov_base = kmap(page);
+			rdata->iov[rdata->nr_iov].iov_len = remaining;
+			cFYI(1, "%u: idx=%lu iov_base=%p iov_len=%zu",
+				rdata->nr_iov, page->index,
+				rdata->iov[rdata->nr_iov].iov_base,
+				rdata->iov[rdata->nr_iov].iov_len);
+			memset(rdata->iov[rdata->nr_iov].iov_base + remaining,
+				'\0', PAGE_CACHE_SIZE - remaining);
+			++rdata->nr_iov;
+			len += remaining;
+			remaining = 0;
+		} else if (page->index > eof_index) {
+			/*
+			 * The VFS will not try to do readahead past the
+			 * i_size, but it's possible that we have outstanding
+			 * writes with gaps in the middle and the i_size hasn't
+			 * caught up yet. Populate those with zeroed out pages
+			 * to prevent the VFS from repeatedly attempting to
+			 * fill them until the writes are flushed.
+			 */
+			zero_user(page, 0, PAGE_CACHE_SIZE);
+			list_del(&page->lru);
+			lru_cache_add_file(page);
+			flush_dcache_page(page);
+			SetPageUptodate(page);
+			unlock_page(page);
+			page_cache_release(page);
+		} else {
+			/* no need to hold page hostage */
+			list_del(&page->lru);
+			lru_cache_add_file(page);
+			unlock_page(page);
+			page_cache_release(page);
+		}
+	}
+
+	return len;
+}
+
 static int cifs_readpages(struct file *file, struct address_space *mapping,
 	struct list_head *page_list, unsigned num_pages)
 {
@@ -2777,6 +2844,7 @@ static int cifs_readpages(struct file *file, struct address_space *mapping,
 		rdata->offset = offset;
 		rdata->bytes = bytes;
 		rdata->pid = pid;
+		rdata->marshal_iov = cifs_readpages_marshal_iov;
 		list_splice_init(&tmplist, &rdata->pages);
 
 		do {