Linux: kmap() not page_address()

Using page_address() will return NULL if the page is in highmem. To
avoid this, we must kmap() the page we're getting the address of,
and kunmap() when we are done. If the page isn't in high memory, then
kmap() is equivalent to page_address().

Change-Id: I42abfadaf3101bf5ad41bd7e5f720ba2583c4ee5
Reviewed-on: http://gerrit.openafs.org/1705
Reviewed-by: Russ Allbery <rra@stanford.edu>
Tested-by: Russ Allbery <rra@stanford.edu>
Reviewed-by: Marc Dionne <marc.c.dionne@gmail.com>
Reviewed-by: Derrick Brashear <shadow@dementia.org>

diff --git a/src/afs/LINUX/osi_fetchstore.c b/src/afs/LINUX/osi_fetchstore.c
index b272c96d22b6ed82fab35f4f369f66cb9f6bebd5..8fb12f1007ad7ab8e98b01c7bb742fc6a98fa6f4 100644 (file)
--- a/src/afs/LINUX/osi_fetchstore.c
+++ b/src/afs/LINUX/osi_fetchstore.c
@@ -64,10 +64,12 @@ afs_linux_splice_actor(struct pipe_inode_info *pipe,
     size = sd->len;
 
     /* Eventually, this could be rx_WritePage */
-    code = rx_Write(svar->call, page_address(buf->page), size);
-    if (code != size) {
-       return -33; /* Can't get a proper rx error out from here */
-    }
+    code = rx_Write(svar->call, kmap(buf->page), size);
+
+    if (code != size)
+       size = -33; /* Can't get a proper rx error out from here */
+
+    kunmap(buf->page);
 
     return size;
 }
@@ -132,7 +134,8 @@ afs_linux_read_actor(read_descriptor_t *desc, struct page *page,
        size = count;
 
     /* Eventually, this could be rx_WritePage */
-    code = rx_Write(svar->call, page_address(page) + offset, size);
+    code = rx_Write(svar->call, kmap(page) + offset, size);
+    kunmap(page);
 
     if (code != size) {
         return -33; /* Can't get a proper rx error out from here */