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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
9cbb4cb21b ("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: Matthew Wilcox <willy@infradead.org>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Matthew Wilcox 2019-03-05 15:44:08 -08:00 committed by Linus Torvalds
parent 67b8046f42
commit 14ef1fc72a
1 changed files with 0 additions and 10 deletions
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10
mm/filemap.c
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@ -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;