The patch titled
Subject: memcg: add mem_cgroup_replace_page_cache() to fix LRU issue
has been added to the -mm tree. Its filename is
memcg-add-mem_cgroup_replace_page_cache-to-fix-lru-issue.patch
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From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
Subject: memcg: add mem_cgroup_replace_page_cache() to fix LRU issue
Commit ef6a3c6311 ("mm: add replace_page_cache_page() function") added a
function replace_page_cache_page(). This function replaces a page in the
radix-tree with a new page. WHen doing this, memory cgroup needs to fix
up the accounting information. memcg need to check PCG_USED bit etc.
In some(many?) cases, 'newpage' is on LRU before calling
replace_page_cache(). So, memcg's LRU accounting information should be
fixed, too.
This patch adds mem_cgroup_replace_page_cache() and removes the old hooks.
In that function, old pages will be unaccounted without touching
res_counter and new page will be accounted to the memcg (of old page).
WHen overwriting pc->mem_cgroup of newpage, take zone->lru_lock and avoid
races with LRU handling.
Background:
replace_page_cache_page() is called by FUSE code in its splice() handling.
Here, 'newpage' is replacing oldpage but this newpage is not a newly allocated
page and may be on LRU. LRU mis-accounting will be critical for memory cgroup
because rmdir() checks the whole LRU is empty and there is no account leak.
If a page is on the other LRU than it should be, rmdir() will fail.
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxx>
Cc: Miklos Szeredi <mszeredi@xxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/memcontrol.h | 6 ++++
mm/filemap.c | 18 +-------------
mm/memcontrol.c | 44 +++++++++++++++++++++++++++++++++++
3 files changed, 52 insertions(+), 16 deletions(-)
diff -puN include/linux/memcontrol.h~memcg-add-mem_cgroup_replace_page_cache-to-fix-lru-issue include/linux/memcontrol.h
--- a/include/linux/memcontrol.h~memcg-add-mem_cgroup_replace_page_cache-to-fix-lru-issue
+++ a/include/linux/memcontrol.h
@@ -119,6 +119,8 @@ struct zone_reclaim_stat*
mem_cgroup_get_reclaim_stat_from_page(struct page *page);
extern void mem_cgroup_print_oom_info(struct mem_cgroup *memcg,
struct task_struct *p);
+extern void mem_cgroup_replace_page_cache(struct page *oldpage,
+ struct page *newpage);
#ifdef CONFIG_CGROUP_MEM_RES_CTLR_SWAP
extern int do_swap_account;
@@ -366,6 +368,10 @@ static inline
void mem_cgroup_count_vm_event(struct mm_struct *mm, enum vm_event_item idx)
{
}
+static inline void mem_cgroup_replace_page_cache(struct page *oldpage,
+ struct page *newpage)
+{
+}
#endif /* CONFIG_CGROUP_MEM_CONT */
#if !defined(CONFIG_CGROUP_MEM_RES_CTLR) || !defined(CONFIG_DEBUG_VM)
diff -puN mm/filemap.c~memcg-add-mem_cgroup_replace_page_cache-to-fix-lru-issue mm/filemap.c
--- a/mm/filemap.c~memcg-add-mem_cgroup_replace_page_cache-to-fix-lru-issue
+++ a/mm/filemap.c
@@ -393,24 +393,11 @@ EXPORT_SYMBOL(filemap_write_and_wait_ran
int replace_page_cache_page(struct page *old, struct page *new, gfp_t gfp_mask)
{
int error;
- struct mem_cgroup *memcg = NULL;
VM_BUG_ON(!PageLocked(old));
VM_BUG_ON(!PageLocked(new));
VM_BUG_ON(new->mapping);
- /*
- * This is not page migration, but prepare_migration and
- * end_migration does enough work for charge replacement.
- *
- * In the longer term we probably want a specialized function
- * for moving the charge from old to new in a more efficient
- * manner.
- */
- error = mem_cgroup_prepare_migration(old, new, &memcg, gfp_mask);
- if (error)
- return error;
-
error = radix_tree_preload(gfp_mask & ~__GFP_HIGHMEM);
if (!error) {
struct address_space *mapping = old->mapping;
@@ -432,13 +419,12 @@ int replace_page_cache_page(struct page
if (PageSwapBacked(new))
__inc_zone_page_state(new, NR_SHMEM);
spin_unlock_irq(&mapping->tree_lock);
+ /* mem_cgroup codes must not be called under tree_lock */
+ mem_cgroup_replace_page_cache(old, new);
radix_tree_preload_end();
if (freepage)
freepage(old);
page_cache_release(old);
- mem_cgroup_end_migration(memcg, old, new, true);
- } else {
- mem_cgroup_end_migration(memcg, old, new, false);
}
return error;
diff -puN mm/memcontrol.c~memcg-add-mem_cgroup_replace_page_cache-to-fix-lru-issue mm/memcontrol.c
--- a/mm/memcontrol.c~memcg-add-mem_cgroup_replace_page_cache-to-fix-lru-issue
+++ a/mm/memcontrol.c
@@ -3366,6 +3366,50 @@ void mem_cgroup_end_migration(struct mem
cgroup_release_and_wakeup_rmdir(&memcg->css);
}
+/*
+ * At replace page cache, newpage is not under any memcg but it's on
+ * LRU. So, this function doesn't touch res_counter but handles LRU
+ * in correct way. Both pages are locked so we cannot race with uncharge.
+ */
+void mem_cgroup_replace_page_cache(struct page *oldpage,
+ struct page *newpage)
+{
+ struct mem_cgroup *memcg;
+ struct page_cgroup *pc;
+ struct zone *zone;
+ enum charge_type type = MEM_CGROUP_CHARGE_TYPE_CACHE;
+ unsigned long flags;
+
+ if (mem_cgroup_disabled())
+ return;
+
+ pc = lookup_page_cgroup(oldpage);
+ /* fix accounting on old pages */
+ lock_page_cgroup(pc);
+ memcg = pc->mem_cgroup;
+ mem_cgroup_charge_statistics(memcg, PageCgroupCache(pc), -1);
+ ClearPageCgroupUsed(pc);
+ unlock_page_cgroup(pc);
+
+ if (PageSwapBacked(oldpage))
+ type = MEM_CGROUP_CHARGE_TYPE_SHMEM;
+
+ zone = page_zone(newpage);
+ pc = lookup_page_cgroup(newpage);
+ /*
+ * Even if newpage->mapping was NULL before starting replacement,
+ * the newpage may be on LRU(or pagevec for LRU) already. We lock
+ * LRU while we overwrite pc->mem_cgroup.
+ */
+ spin_lock_irqsave(&zone->lru_lock, flags);
+ if (PageLRU(newpage))
+ del_page_from_lru_list(zone, newpage, page_lru(newpage));
+ __mem_cgroup_commit_charge(memcg, newpage, 1, pc, type);
+ if (PageLRU(newpage))
+ add_page_to_lru_list(zone, newpage, page_lru(newpage));
+ spin_unlock_irqrestore(&zone->lru_lock, flags);
+}
+
#ifdef CONFIG_DEBUG_VM
static struct page_cgroup *lookup_page_cgroup_used(struct page *page)
{
_
Subject: Subject: memcg: add mem_cgroup_replace_page_cache() to fix LRU issue
Patches currently in -mm which might be from kamezawa.hiroyu@xxxxxxxxxxxxxx are
origin.patch
linux-next.patch
memcg-add-mem_cgroup_replace_page_cache-to-fix-lru-issue.patch
vmscan-promote-shared-file-mapped-pages.patch
vmscan-activate-executable-pages-after-first-usage.patch
mm-avoid-livelock-on-__gfp_fs-allocations-v2.patch
mm-hugetlbc-fix-virtual-address-handling-in-hugetlb-fault.patch
mm-hugetlbc-fix-virtual-address-handling-in-hugetlb-fault-fix.patch
vmscan-add-task-name-to-warn_scan_unevictable-messages.patch
mm-exclude-reserved-pages-from-dirtyable-memory.patch
mm-exclude-reserved-pages-from-dirtyable-memory-fix.patch
mm-writeback-cleanups-in-preparation-for-per-zone-dirty-limits.patch
mm-try-to-distribute-dirty-pages-fairly-across-zones.patch
mm-filemap-pass-__gfp_write-from-grab_cache_page_write_begin.patch
btrfs-pass-__gfp_write-for-buffered-write-page-allocations.patch
cgroup-fix-task-counter-common-ancestor-logic.patch
mm-memcg-consolidate-hierarchy-iteration-primitives.patch
mm-vmscan-distinguish-global-reclaim-from-global-lru-scanning.patch
mm-vmscan-distinguish-between-memcg-triggering-reclaim-and-memcg-being-scanned.patch
mm-memcg-per-priority-per-zone-hierarchy-scan-generations.patch
mm-move-memcg-hierarchy-reclaim-to-generic-reclaim-code.patch
mm-memcg-remove-optimization-of-keeping-the-root_mem_cgroup-lru-lists-empty.patch
mm-vmscan-convert-global-reclaim-to-per-memcg-lru-lists.patch
mm-collect-lru-list-heads-into-struct-lruvec.patch
mm-make-per-memcg-lru-lists-exclusive.patch
mm-memcg-remove-unused-node-section-info-from-pc-flags.patch
mm-memcg-remove-unused-node-section-info-from-pc-flags-fix.patch
memcg-make-mem_cgroup_split_huge_fixup-more-efficient.patch
memcg-make-mem_cgroup_split_huge_fixup-more-efficient-fix.patch
mm-memcg-shorten-preempt-disabled-section-around-event-checks.patch
documentation-cgroups-memorytxt-fix-typo.patch
memcg-fix-pgpgin-pgpgout-documentation.patch
mm-oom_kill-remove-memcg-argument-from-oom_kill_task.patch
mm-unify-remaining-mem_cont-mem-etc-variable-names-to-memcg.patch
mm-memcg-clean-up-fault-accounting.patch
mm-memcg-lookup_page_cgroup-almost-never-returns-null.patch
mm-page_cgroup-check-page_cgroup-arrays-in-lookup_page_cgroup-only-when-necessary.patch
mm-memcg-remove-unneeded-checks-from-newpage_charge.patch
mm-memcg-remove-unneeded-checks-from-uncharge_page.patch
page_cgroup-add-helper-function-to-get-swap_cgroup.patch
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