kernel/kfifo.c: add handling of chained scatterlists

The current kfifo scatterlist implementation will not work with chained
scatterlists.  It assumes that struct scatterlist arrays are allocated
contiguously, which is not the case when chained scatterlists (struct
sg_table) are in use.
Signed-off-by: Stefani Seibold <stefani@seibold.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

kernel/kfifo.c

@@ -10,7 +10,7 @@
  *
  * This program is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  * GNU General Public License for more details.
  *
  * You should have received a copy of the GNU General Public License
@@ -333,17 +333,16 @@ static int setup_sgl_buf(struct scatterlist *sgl, void *buf,
 		buf += PAGE_SIZE;
 		npage = virt_to_page(buf);
 		if (page_to_phys(page) != page_to_phys(npage) - l) {
-			sgl->page_link = 0;
-			sg_set_page(sgl++, page, l - off, off);
-			if (++n == nents)
+			sg_set_page(sgl, page, l - off, off);
+			sgl = sg_next(sgl);
+			if (++n == nents || sgl == NULL)
 				return n;
 			page = npage;
 			len -= l - off;
 			l = off = 0;
 		}
 	}
-	sgl->page_link = 0;
-	sg_set_page(sgl++, page, len, off);
+	sg_set_page(sgl, page, len, off);
 	return n + 1;
 }
 
@@ -363,7 +362,7 @@ static unsigned int setup_sgl(struct __kfifo *fifo, struct scatterlist *sgl,
 	}
 	l = min(len, size - off);
 
-	n  = setup_sgl_buf(sgl, fifo->data + off, nents, l);
+	n = setup_sgl_buf(sgl, fifo->data + off, nents, l);
 	n += setup_sgl_buf(sgl + n, fifo->data, nents - n, len - l);
 
 	if (n)