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

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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>
This commit is contained in:
zhong jiang 2019-11-30 17:49:50 -08:00 committed by Linus Torvalds
parent 9266a14033
commit b96cc65515
1 changed files with 5 additions and 3 deletions
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8
mm/gup.c
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@ -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,