CIFS: Use offset when reading pages

With offset defined in rdata, transport functions need to look at this
offset when reading data into the correct places in pages.
Signed-off-by: Long Li <longli@microsoft.com>
Signed-off-by: Steve French <smfrench@gmail.com>

fs/cifs/cifsproto.h

@@ -203,7 +203,9 @@ extern void dequeue_mid(struct mid_q_entry *mid, bool malformed);
 extern int cifs_read_from_socket(struct TCP_Server_Info *server, char *buf,
 			         unsigned int to_read);
 extern int cifs_read_page_from_socket(struct TCP_Server_Info *server,
-				      struct page *page, unsigned int to_read);
+					struct page *page,
+					unsigned int page_offset,
+					unsigned int to_read);
 extern int cifs_setup_cifs_sb(struct smb_vol *pvolume_info,
 			       struct cifs_sb_info *cifs_sb);
 extern int cifs_match_super(struct super_block *, void *);

fs/cifs/connect.c

@@ -599,10 +599,11 @@ cifs_read_from_socket(struct TCP_Server_Info *server, char *buf,
 
 int
 cifs_read_page_from_socket(struct TCP_Server_Info *server, struct page *page,
-		      unsigned int to_read)
+	unsigned int page_offset, unsigned int to_read)
 {
 	struct msghdr smb_msg;
-	struct bio_vec bv = {.bv_page = page, .bv_len = to_read};
+	struct bio_vec bv = {
+		.bv_page = page, .bv_len = to_read, .bv_offset = page_offset};
 	iov_iter_bvec(&smb_msg.msg_iter, READ | ITER_BVEC, &bv, 1, to_read);
 	return cifs_readv_from_socket(server, &smb_msg);
 }

fs/cifs/file.c

@@ -3026,12 +3026,20 @@ uncached_fill_pages(struct TCP_Server_Info *server,
 	int result = 0;
 	unsigned int i;
 	unsigned int nr_pages = rdata->nr_pages;
+	unsigned int page_offset = rdata->page_offset;
 
 	rdata->got_bytes = 0;
 	rdata->tailsz = PAGE_SIZE;
 	for (i = 0; i < nr_pages; i++) {
 		struct page *page = rdata->pages[i];
 		size_t n;
+		unsigned int segment_size = rdata->pagesz;
+
+		if (i == 0)
+			segment_size -= page_offset;
+		else
+			page_offset = 0;
+
 
 		if (len <= 0) {
 			/* no need to hold page hostage */
@@ -3040,24 +3048,25 @@ uncached_fill_pages(struct TCP_Server_Info *server,
 			put_page(page);
 			continue;
 		}
+
 		n = len;
-		if (len >= PAGE_SIZE) {
+		if (len >= segment_size)
 			/* enough data to fill the page */
-			n = PAGE_SIZE;
-			len -= n;
-		} else {
-			zero_user(page, len, PAGE_SIZE - len);
+			n = segment_size;
+		else
 			rdata->tailsz = len;
-			len = 0;
-		}
+		len -= n;
+
 		if (iter)
-			result = copy_page_from_iter(page, 0, n, iter);
+			result = copy_page_from_iter(
+					page, page_offset, n, iter);
 #ifdef CONFIG_CIFS_SMB_DIRECT
 		else if (rdata->mr)
 			result = n;
 #endif
 		else
-			result = cifs_read_page_from_socket(server, page, n);
+			result = cifs_read_page_from_socket(
+					server, page, page_offset, n);
 		if (result < 0)
 			break;
 
@@ -3130,6 +3139,7 @@ cifs_send_async_read(loff_t offset, size_t len, struct cifsFileInfo *open_file,
 		rdata->bytes = cur_len;
 		rdata->pid = pid;
 		rdata->pagesz = PAGE_SIZE;
+		rdata->tailsz = PAGE_SIZE;
 		rdata->read_into_pages = cifs_uncached_read_into_pages;
 		rdata->copy_into_pages = cifs_uncached_copy_into_pages;
 		rdata->credits = credits;
@@ -3574,6 +3584,7 @@ readpages_fill_pages(struct TCP_Server_Info *server,
 	u64 eof;
 	pgoff_t eof_index;
 	unsigned int nr_pages = rdata->nr_pages;
+	unsigned int page_offset = rdata->page_offset;
 
 	/* determine the eof that the server (probably) has */
 	eof = CIFS_I(rdata->mapping->host)->server_eof;
@@ -3584,13 +3595,21 @@ readpages_fill_pages(struct TCP_Server_Info *server,
 	rdata->tailsz = PAGE_SIZE;
 	for (i = 0; i < nr_pages; i++) {
 		struct page *page = rdata->pages[i];
-		size_t n = PAGE_SIZE;
+		unsigned int to_read = rdata->pagesz;
+		size_t n;
+
+		if (i == 0)
+			to_read -= page_offset;
+		else
+			page_offset = 0;
+
+		n = to_read;
 
-		if (len >= PAGE_SIZE) {
-			len -= PAGE_SIZE;
+		if (len >= to_read) {
+			len -= to_read;
 		} else if (len > 0) {
 			/* enough for partial page, fill and zero the rest */
-			zero_user(page, len, PAGE_SIZE - len);
+			zero_user(page, len + page_offset, to_read - len);
 			n = rdata->tailsz = len;
 			len = 0;
 		} else if (page->index > eof_index) {
@@ -3622,13 +3641,15 @@ readpages_fill_pages(struct TCP_Server_Info *server,
 		}
 
 		if (iter)
-			result = copy_page_from_iter(page, 0, n, iter);
+			result = copy_page_from_iter(
+					page, page_offset, n, iter);
 #ifdef CONFIG_CIFS_SMB_DIRECT
 		else if (rdata->mr)
 			result = n;
 #endif
 		else
-			result = cifs_read_page_from_socket(server, page, n);
+			result = cifs_read_page_from_socket(
+					server, page, page_offset, n);
 		if (result < 0)
 			break;
 
@@ -3807,6 +3828,7 @@ static int cifs_readpages(struct file *file, struct address_space *mapping,
 		rdata->bytes = bytes;
 		rdata->pid = pid;
 		rdata->pagesz = PAGE_SIZE;
+		rdata->tailsz = PAGE_SIZE;
 		rdata->read_into_pages = cifs_readpages_read_into_pages;
 		rdata->copy_into_pages = cifs_readpages_copy_into_pages;
 		rdata->credits = credits;

fs/cifs/smb2ops.c

@@ -2483,7 +2483,7 @@ read_data_into_pages(struct TCP_Server_Info *server, struct page **pages,
 			zero_user(page, len, PAGE_SIZE - len);
 			len = 0;
 		}
-		length = cifs_read_page_from_socket(server, page, n);
+		length = cifs_read_page_from_socket(server, page, 0, n);
 		if (length < 0)
 			return length;
 		server->total_read += length;

fs/cifs/smb2pdu.c

@@ -2781,6 +2781,7 @@ smb2_readv_callback(struct mid_q_entry *mid)
 	struct smb_rqst rqst = { .rq_iov = rdata->iov,
 				 .rq_nvec = 2,
 				 .rq_pages = rdata->pages,
+				 .rq_offset = rdata->page_offset,
 				 .rq_npages = rdata->nr_pages,
 				 .rq_pagesz = rdata->pagesz,
 				 .rq_tailsz = rdata->tailsz };