[patch] filemap_getpage can block when MAP_NONBLOCK specified

[Jeff Moyer]

Hello,

We will return NULL from filemap_getpage when a page does not exist in the
page cache and MAP_NONBLOCK is specified, here:

        page = find_get_page(mapping, pgoff);
        if (!page) {
                if (nonblock)
                        return NULL;
                goto no_cached_page;
        }

But we forget to do so when the page in the cache is not uptodate.  The
following could result in a blocking call:

        /*
         * Ok, found a page in the page cache, now we need to check
         * that it's up-to-date.
         */
        if (!PageUptodate(page))
                goto page_not_uptodate;

Patch attached.

Thanks,

Jeff

--- linux-2.6.11/mm/filemap.c.orig      2005-03-30 14:57:02.252975936 -0500
+++ linux-2.6.11/mm/filemap.c   2005-03-30 15:02:51.808835368 -0500
@@ -1379,8 +1379,13 @@ retry_find:
         * Ok, found a page in the page cache, now we need to check
         * that it's up-to-date.
         */
-       if (!PageUptodate(page))
+       if (!PageUptodate(page)) {
+               if (nonblock) {
+                       page_cache_release(page);
+                       return NULL;
+               }
                goto page_not_uptodate;
+       }
 
 success:
        /*
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [EMAIL PROTECTED]
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/