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Commit 9cbb4cb2 authored by Nick Piggin's avatar Nick Piggin Committed by Linus Torvalds
Browse files

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: default avatarNick Piggin <npiggin@kernel.dk>
Reviewed-by: default avatarWu Fengguang <fengguang.wu@intel.com>
Reviewed-by: default avatarMinchan Kim <minchan.kim@gmail.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent f0bc0a60

mm/filemap.c

+10 −3
Original line number Diff line number Diff line
@@ -837,9 +837,6 @@ unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t index, 
		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 @@ unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t index, 
			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++;