The patch titled
Subject: mm: memcontrol: update mem_cgroup_page_lruvec() documentation
has been removed from the -mm tree. Its filename was
mm-memcontrol-update-mem_cgroup_page_lruvec-documentation.patch
This patch was dropped because it was merged into mainline or a subsystem tree
------------------------------------------------------
From: Johannes Weiner <hannes@xxxxxxxxxxx>
Subject: mm: memcontrol: update mem_cgroup_page_lruvec() documentation
7512102cf64d ("memcg: fix GPF when cgroup removal races with last exit")
added a pc->mem_cgroup reset into mem_cgroup_page_lruvec() to prevent a
crash where an anon page gets uncharged on unmap, the memcg is released,
and then the final LRU isolation on free dereferences the stale
pc->mem_cgroup pointer.
But since 0a31bc97c80c ("mm: memcontrol: rewrite uncharge API"), pages are
only uncharged AFTER that final LRU isolation, which guarantees the
memcg's lifetime until then. pc->mem_cgroup now only needs to be reset
for swapcache readahead pages.
Update the comment and callsite requirements accordingly.
Signed-off-by: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/memcontrol.c | 16 ++++++++--------
1 file changed, 8 insertions(+), 8 deletions(-)
diff -puN mm/memcontrol.c~mm-memcontrol-update-mem_cgroup_page_lruvec-documentation mm/memcontrol.c
--- a/mm/memcontrol.c~mm-memcontrol-update-mem_cgroup_page_lruvec-documentation
+++ a/mm/memcontrol.c
@@ -1262,9 +1262,13 @@ out:
}
/**
- * mem_cgroup_page_lruvec - return lruvec for adding an lru page
+ * mem_cgroup_page_lruvec - return lruvec for isolating/putting an LRU page
* @page: the page
* @zone: zone of the page
+ *
+ * This function is only safe when following the LRU page isolation
+ * and putback protocol: the LRU lock must be held, and the page must
+ * either be PageLRU() or the caller must have isolated/allocated it.
*/
struct lruvec *mem_cgroup_page_lruvec(struct page *page, struct zone *zone)
{
@@ -1282,13 +1286,9 @@ struct lruvec *mem_cgroup_page_lruvec(st
memcg = pc->mem_cgroup;
/*
- * Surreptitiously switch any uncharged offlist page to root:
- * an uncharged page off lru does nothing to secure
- * its former mem_cgroup from sudden removal.
- *
- * Our caller holds lru_lock, and PageCgroupUsed is updated
- * under page_cgroup lock: between them, they make all uses
- * of pc->mem_cgroup safe.
+ * Swapcache readahead pages are added to the LRU - and
+ * possibly migrated - before they are charged. Ensure
+ * pc->mem_cgroup is sane.
*/
if (!PageLRU(page) && !PageCgroupUsed(pc) && memcg != root_mem_cgroup)
pc->mem_cgroup = memcg = root_mem_cgroup;
_
Patches currently in -mm which might be from hannes@xxxxxxxxxxx are
origin.patch
memcg-__mem_cgroup_free-remove-stale-disarm_static_keys-comment.patch
memcg-dont-check-mm-in-__memcg_kmem_get_cachenewpage_charge.patch
memcg-do-not-abuse-memcg_kmem_skip_account.patch
mm-page_allocc-__alloc_pages_nodemask-dont-alter-arg-gfp_mask.patch
mm-mincore-add-hwpoison-page-handle.patch
memcg-zap-kmem_account_flags.patch
memcg-only-check-memcg_kmem_skip_account-in-__memcg_kmem_get_cache.patch
memcg-turn-memcg_kmem_skip_account-into-a-bit-field.patch
mm-move-swp_entry_t-definition-to-include-linux-mm_typesh.patch
mm-gfp-escalatedly-define-gfp_highuser-and-gfp_highuser_movable.patch
mm-page_ext-resurrect-struct-page-extending-code-for-debugging.patch
mm-page_ext-resurrect-struct-page-extending-code-for-debugging-fix.patch
mm-debug-pagealloc-prepare-boottime-configurable-on-off.patch
mm-debug-pagealloc-make-debug-pagealloc-boottime-configurable.patch
mm-debug-pagealloc-make-debug-pagealloc-boottime-configurable-fix.patch
mm-nommu-use-alloc_pages_exact-rather-than-its-own-implementation.patch
stacktrace-introduce-snprint_stack_trace-for-buffer-output.patch
mm-page_owner-keep-track-of-page-owners.patch
mm-page_owner-correct-owner-information-for-early-allocated-pages.patch
documentation-add-new-page_owner-document.patch
mm-vmscan-invoke-slab-shrinkers-from-shrink_zone.patch
mm-vmscan-invoke-slab-shrinkers-from-shrink_zone-fix.patch
mm-page_alloc-embed-oom-killing-naturally-into-allocation-slowpath.patch
mm-memcontrol-fix-defined-but-not-used-compiler-warning.patch
memcg-fix-possible-use-after-free-in-memcg_kmem_get_cache.patch
mm-memcontrolc-cleaning-up-function-that-are-not-used-anywhere.patch
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