Commit b96cc655 authored Nov 30, 2019 by zhong jiang Committed by Linus Torvalds Dec 01, 2019

mm/gup.c: allow CMA migration to propagate errors back to caller

check_and_migrate_cma_pages() was recording the result of
__get_user_pages_locked() in an unsigned "nr_pages" variable.

Because __get_user_pages_locked() returns a signed value that can
include negative errno values, this had the effect of hiding errors.

Change check_and_migrate_cma_pages() implementation so that it uses a
signed variable instead, and propagates the results back to the caller
just as other gup internal functions do.

This was discovered with the help of unsigned_lesser_than_zero.cocci.

Link: http://lkml.kernel.org/r/1571671030-58029-1-git-send-email-zhongjiang@huawei.com


Signed-off-by: zhong jiang <zhongjiang@huawei.com>
Suggested-by: John Hubbard <jhubbard@nvidia.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 9266a140

mm/gup.c

+5 −3

Original line number	Diff line number	Diff line
		@@ -1443,6 +1443,7 @@ static long check_and_migrate_cma_pages(struct task_struct *tsk,
		bool drain_allow = true;
		bool migrate_allow = true;
		LIST_HEAD(cma_page_list);
		long ret = nr_pages;

		check_again:
		for (i = 0; i < nr_pages;) {
		@@ -1504,17 +1505,18 @@ check_again:
		* again migrating any new CMA pages which we failed to isolate
		* earlier.
		*/
		nr_pages = __get_user_pages_locked(tsk, mm, start, nr_pages,
		ret = __get_user_pages_locked(tsk, mm, start, nr_pages,
		pages, vmas, NULL,
		gup_flags);

		if ((nr_pages > 0) && migrate_allow) {
		if ((ret > 0) && migrate_allow) {
		nr_pages = ret;
		drain_allow = true;
		goto check_again;
		}
		}

		return nr_pages;
		return ret;
		}
		#else
		static long check_and_migrate_cma_pages(struct task_struct *tsk,

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