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authorNick Piggin <npiggin@kernel.dk>2011-01-13 15:45:51 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2011-01-13 17:32:32 -0800
commit9cbb4cb21b19fff46cf1174d0ed699ef710e641c (patch)
tree56480b1f4082d6158f077378db36c99d6d3ff209 /mm/filemap.c
parentf0bc0a60b13f209df16062f94e9fb4b90dc08708 (diff)
downloadlwn-9cbb4cb21b19fff46cf1174d0ed699ef710e641c.tar.gz
lwn-9cbb4cb21b19fff46cf1174d0ed699ef710e641c.zip
mm: find_get_pages_contig fixlet
Testing ->mapping and ->index without a ref is not stable as the page may have been reused at this point. Signed-off-by: Nick Piggin <npiggin@kernel.dk> Reviewed-by: Wu Fengguang <fengguang.wu@intel.com> Reviewed-by: Minchan Kim <minchan.kim@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/filemap.c')
-rw-r--r--mm/filemap.c13
1 files changed, 10 insertions, 3 deletions
diff --git a/mm/filemap.c b/mm/filemap.c
index ca389394fa2a..1a3dd5914726 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -837,9 +837,6 @@ repeat:
if (radix_tree_deref_retry(page))
goto restart;
- if (page->mapping == NULL || page->index != index)
- break;
-
if (!page_cache_get_speculative(page))
goto repeat;
@@ -849,6 +846,16 @@ repeat:
goto repeat;
}
+ /*
+ * must check mapping and index after taking the ref.
+ * otherwise we can get both false positives and false
+ * negatives, which is just confusing to the caller.
+ */
+ if (page->mapping == NULL || page->index != index) {
+ page_cache_release(page);
+ break;
+ }
+
pages[ret] = page;
ret++;
index++;