mm/vmscan.c: fix unsequenced modification and access warning

commit f2f43e566a02a3bdde0a65e6a2e88d707c212a29 upstream.

Clang and its -Wunsequenced emits a warning

  mm/vmscan.c:2961:25: error: unsequenced modification and access to 'gfp_mask' [-Wunsequenced]
                  .gfp_mask = (gfp_mask = current_gfp_context(gfp_mask)),
                                        ^

While it is not clear to me whether the initialization code violates the
specification (6.7.8 par 19 (ISO/IEC 9899) looks like it disagrees) the
code is quite confusing and worth cleaning up anyway.  Fix this by
reusing sc.gfp_mask rather than the updated input gfp_mask parameter.

Link: http://lkml.kernel.org/r/20170510154030.10720-1-nick.desaulniers@gmail.com
Signed-off-by: Nick Desaulniers <nick.desaulniers@gmail.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
[natechancellor: Adjust context due to abscence of 7dea19f9ee63]
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/mm/vmscan.c b/mm/vmscan.c
index cdd5c3b..557ad13 100644 (file)
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2966,7 +2966,7 @@ unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
        unsigned long nr_reclaimed;
        struct scan_control sc = {
                .nr_to_reclaim = SWAP_CLUSTER_MAX,
-               .gfp_mask = (gfp_mask = memalloc_noio_flags(gfp_mask)),
+               .gfp_mask = memalloc_noio_flags(gfp_mask),
                .reclaim_idx = gfp_zone(gfp_mask),
                .order = order,
                .nodemask = nodemask,
@@ -2981,12 +2981,12 @@ unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
         * 1 is returned so that the page allocator does not OOM kill at this
         * point.
         */
-       if (throttle_direct_reclaim(gfp_mask, zonelist, nodemask))
+       if (throttle_direct_reclaim(sc.gfp_mask, zonelist, nodemask))
                return 1;
 
        trace_mm_vmscan_direct_reclaim_begin(order,
                                sc.may_writepage,
-                               gfp_mask,
+                               sc.gfp_mask,
                                sc.reclaim_idx);
 
        nr_reclaimed = do_try_to_free_pages(zonelist, &sc);
@@ -3749,16 +3749,15 @@ static int __node_reclaim(struct pglist_data *pgdat, gfp_t gfp_mask, unsigned in
        const unsigned long nr_pages = 1 << order;
        struct task_struct *p = current;
        struct reclaim_state reclaim_state;
-       int classzone_idx = gfp_zone(gfp_mask);
        struct scan_control sc = {
                .nr_to_reclaim = max(nr_pages, SWAP_CLUSTER_MAX),
-               .gfp_mask = (gfp_mask = memalloc_noio_flags(gfp_mask)),
+               .gfp_mask = memalloc_noio_flags(gfp_mask),
                .order = order,
                .priority = NODE_RECLAIM_PRIORITY,
                .may_writepage = !!(node_reclaim_mode & RECLAIM_WRITE),
                .may_unmap = !!(node_reclaim_mode & RECLAIM_UNMAP),
                .may_swap = 1,
-               .reclaim_idx = classzone_idx,
+               .reclaim_idx = gfp_zone(gfp_mask),
        };
 
        cond_resched();
@@ -3768,7 +3767,7 @@ static int __node_reclaim(struct pglist_data *pgdat, gfp_t gfp_mask, unsigned in
         * and RECLAIM_UNMAP.
         */
        p->flags |= PF_MEMALLOC | PF_SWAPWRITE;
-       lockdep_set_current_reclaim_state(gfp_mask);
+       lockdep_set_current_reclaim_state(sc.gfp_mask);
        reclaim_state.reclaimed_slab = 0;
        p->reclaim_state = &reclaim_state;