From: Jeff Moyer 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 --- 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 Wed Mar 30 15:56:23 2005 +++ 25-akpm/mm/filemap.c Wed Mar 30 15:56:23 2005 @@ -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: /* _