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Subject[patch 015/198] filemap_getpage can block when MAP_NONBLOCK specified
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From: Jeff Moyer <jmoyer@redhat.com>

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;


Signed-off-by: Andrew Morton <akpm@osdl.org>
---
25-akpm/mm/filemap.c | 7 ++++++-
1 files changed, 6 insertions(+), 1 deletion(-)
diff -puN mm/filemap.c~filemap_getpage-can-block-when-map_nonblock-specified mm/filemap.c
--- 25/mm/filemap.c~filemap_getpage-can-block-when-map_nonblock-specified 2005-04-12 03:21:07.024069080 -0700
+++ 25-akpm/mm/filemap.c 2005-04-12 03:21:07.028068472 -0700
@@ -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:
/*
_
-
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