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Commit 14ef1fc7 authored by Matthew Wilcox's avatar Matthew Wilcox Committed by Linus Torvalds
Browse files

mm/filemap.c: remove redundant test from find_get_pages_contig 

After we establish a reference on the page, we check the pointer
continues to be in the correct position in i_pages.  Checking
page->index afterwards is unnecessary; if it were to change, then the
pointer to it from the page cache would also move.  The check used to be
done before grabbing a reference on the page which was racy (see commit
9cbb4cb2 ("mm: find_get_pages_contig fixlet")), but nobody noticed
that moving the check after grabbing the reference was redundant.

Link: http://lkml.kernel.org/r/20190107200224.13260-1-willy@infradead.org


Signed-off-by: default avatarMatthew Wilcox <willy@infradead.org>
Reviewed-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 67b8046f

mm/filemap.c

+0 −10
Original line number Diff line number Diff line
@@ -1837,16 +1837,6 @@ unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t index, 
		if (unlikely(page != xas_reload(&xas)))

			goto put_page;



		/*

		 * 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 || page_to_pgoff(page) != xas.xa_index) {

			put_page(page);

			break;

		}



		pages[ret] = page;

		if (++ret == nr_pages)

			break;