[PATCH] valid_swaphandles() fix (3f9e7949) · Commits · 戴 / test

akpm draws my attention to the fact that sysctl(VM_PAGE_CLUSTER) might conceivably change page_cluster to 0 while valid_swaphandles() is in the middle of using it, leading to an embarrassingly long loop: take a local snapshot of page_cluster and work with that. Signed-off-by:

Hugh Dickins <hugh@veritas.com> Signed-off-by:

Andrew Morton <akpm@osdl.org> Signed-off-by:

Linus Torvalds <torvalds@osdl.org>

mm/swapfile.c

+4 −3

Original line number	Diff line number	Diff line
		@@ -1723,13 +1723,14 @@ get_swap_info_struct(unsigned type)
		*/
		int valid_swaphandles(swp_entry_t entry, unsigned long *offset)
		{
		int ret = 0, i = 1 << page_cluster;
		int our_page_cluster = page_cluster;
		int ret = 0, i = 1 << our_page_cluster;
		unsigned long toff;
		struct swap_info_struct *swapdev = swp_type(entry) + swap_info;

		if (!page_cluster) /* no readahead */
		if (!our_page_cluster) /* no readahead */
		return 0;
		toff = (swp_offset(entry) >> page_cluster) << page_cluster;
		toff = (swp_offset(entry) >> our_page_cluster) << our_page_cluster;
		if (!toff) /* first page is swap header */
		toff++, i--;
		*offset = toff;

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