[merged] vmscan-fix-zone-shrinking-exit-when-scan-work-is-done.patch removed from -mm tree

[merged] vmscan-fix-zone-shrinking-exit-when-scan-work-is-done.patch removed from -mm tree

[akpm]

The patch titled
     vmscan: fix zone shrinking exit when scan work is done
has been removed from the -mm tree.  Its filename was
     vmscan-fix-zone-shrinking-exit-when-scan-work-is-done.patch

This patch was dropped because it was merged into mainline or a subsystem tree

The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/

------------------------------------------------------
Subject: vmscan: fix zone shrinking exit when scan work is done
From: Johannes Weiner <hannes@cmpxchg.org>

3e7d344 ("mm: vmscan: reclaim order-0 and use compaction instead of lumpy
reclaim") introduced an indefinite loop in shrink_zone().

It meant to break out of this loop when no pages had been reclaimed and
not a single page was even scanned.  The way it would detect the latter is
by taking a snapshot of sc->nr_scanned at the beginning of the function
and comparing it against the new sc->nr_scanned after the scan loop.  But
it would re-iterate without updating that snapshot, looping forever if
sc->nr_scanned changed at least once since shrink_zone() was invoked.

This is not the sole condition that would exit that loop, but it requires
other processes to change the zone state, as the reclaimer that is stuck
obviously can not anymore.

This is only happening for higher-order allocations, where reclaim is run
back to back with compaction.

Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reported-by: Michal Hocko <mhocko@suse.cz>
Tested-by: Kent Overstreet<kent.overstreet@gmail.com>
Reported-by: Kent Overstreet <kent.overstreet@gmail.com>
Acked-by: Mel Gorman <mel@csn.ul.ie>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Rik van Riel <riel@redhat.com>
Reviewed-by: Minchan Kim <minchan.kim@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/vmscan.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff -puN mm/vmscan.c~vmscan-fix-zone-shrinking-exit-when-scan-work-is-done mm/vmscan.c
--- a/mm/vmscan.c~vmscan-fix-zone-shrinking-exit-when-scan-work-is-done
+++ a/mm/vmscan.c
@@ -1882,12 +1882,12 @@ static void shrink_zone(int priority, st
 	unsigned long nr[NR_LRU_LISTS];
 	unsigned long nr_to_scan;
 	enum lru_list l;
-	unsigned long nr_reclaimed;
+	unsigned long nr_reclaimed, nr_scanned;
 	unsigned long nr_to_reclaim = sc->nr_to_reclaim;
-	unsigned long nr_scanned = sc->nr_scanned;
 
 restart:
 	nr_reclaimed = 0;
+	nr_scanned = sc->nr_scanned;
 	get_scan_count(zone, sc, nr, priority);
 
 	while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] ||
_

Patches currently in -mm which might be from hannes@cmpxchg.org are

origin.patch
mm-introduce-delete_from_page_cache.patch
mm-hugetlbfs-change-remove_from_page_cache.patch
mm-shmem-change-remove_from_page_cache.patch
mm-truncate-change-remove_from_page_cache.patch
mm-good-bye-remove_from_page_cache.patch
mm-change-__remove_from_page_cache.patch
mm-batch-free-pcp-list-if-possible.patch
mm-batch-free-pcp-list-if-possible-fix.patch
epoll-fix-compiler-warning-and-optimize-the-non-blocking-path-fix.patch
memcg-res_counter_read_u64-fix-potential-races-on-32-bit-machines.patch
memcg-fix-ugly-initialization-of-return-value-is-in-caller.patch
memcg-soft-limit-reclaim-should-end-at-limit-not-below.patch
memcg-simplify-the-way-memory-limits-are-checked.patch
memcg-remove-unused-page-flag-bitfield-defines.patch
memcg-remove-impossible-conditional-when-committing.patch
memcg-remove-null-check-from-lookup_page_cgroup-result.patch
memcg-add-memcg-sanity-checks-at-allocating-and-freeing-pages.patch
memcg-add-memcg-sanity-checks-at-allocating-and-freeing-pages-update.patch
memcg-no-uncharged-pages-reach-page_cgroup_zoneinfo.patch
memcg-change-page_cgroup_zoneinfo-signature.patch
memcg-fold-__mem_cgroup_move_account-into-caller.patch
memcg-condense-page_cgroup-to-page-lookup-points.patch
memcg-remove-direct-page_cgroup-to-page-pointer.patch
memcg-remove-direct-page_cgroup-to-page-pointer-fix.patch
memcg-remove-direct-page_cgroup-to-page-pointer-fix-fix.patch
memcg-charged-pages-always-have-valid-per-memcg-zone-info.patch
memcg-remove-memcg-reclaim_param_lock.patch
memcg-keep-only-one-charge-cancelling-function.patch
memcg-keep-only-one-charge-cancelling-function-fix.patch
memcg-convert-per-cpu-stock-from-bytes-to-page-granularity.patch
memcg-convert-uncharge-batching-from-bytes-to-page-granularity.patch
memcg-unify-charge-uncharge-quantities-to-units-of-pages.patch
crash_dump-export-is_kdump_kernel-to-modules-consolidate-elfcorehdr_addr-setup_elfcorehdr-and-saved_max_pfn.patch
crash_dump-export-is_kdump_kernel-to-modules-consolidate-elfcorehdr_addr-setup_elfcorehdr-and-saved_max_pfn-fix.patch
crash_dump-export-is_kdump_kernel-to-modules-consolidate-elfcorehdr_addr-setup_elfcorehdr-and-saved_max_pfn-fix-fix.patch