[patch] mm: memcontrol: rewrite charge API fix - hugetlb charging

From: Johannes Weiner
Date: Wed Jul 16 2014 - 12:28:17 EST


Naoya-san reports that hugetlb pages now get charged as file cache,
which wreaks all kinds of havoc during migration, uncharge etc.

The file-specific charge path used to filter PageCompound(), but it
wasn't commented and so it got lost when unifying the charge paths.

We can't add PageCompound() back into a unified charge path because of
THP, so filter huge pages directly in add_to_page_cache().

Reported-by: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
Signed-off-by: Johannes Weiner <hannes@xxxxxxxxxxx>
---
mm/filemap.c | 20 ++++++++++++++------
1 file changed, 14 insertions(+), 6 deletions(-)

diff --git a/mm/filemap.c b/mm/filemap.c
index 114cd89c1cc2..c088ac01e856 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -31,6 +31,7 @@
#include <linux/security.h>
#include <linux/cpuset.h>
#include <linux/hardirq.h> /* for BUG_ON(!in_atomic()) only */
+#include <linux/hugetlb.h>
#include <linux/memcontrol.h>
#include <linux/cleancache.h>
#include <linux/rmap.h>
@@ -560,19 +561,24 @@ static int __add_to_page_cache_locked(struct page *page,
pgoff_t offset, gfp_t gfp_mask,
void **shadowp)
{
+ int huge = PageHuge(page);
struct mem_cgroup *memcg;
int error;

VM_BUG_ON_PAGE(!PageLocked(page), page);
VM_BUG_ON_PAGE(PageSwapBacked(page), page);

- error = mem_cgroup_try_charge(page, current->mm, gfp_mask, &memcg);
- if (error)
- return error;
+ if (!huge) {
+ error = mem_cgroup_try_charge(page, current->mm,
+ gfp_mask, &memcg);
+ if (error)
+ return error;
+ }

error = radix_tree_maybe_preload(gfp_mask & ~__GFP_HIGHMEM);
if (error) {
- mem_cgroup_cancel_charge(page, memcg);
+ if (!huge)
+ mem_cgroup_cancel_charge(page, memcg);
return error;
}

@@ -587,14 +593,16 @@ static int __add_to_page_cache_locked(struct page *page,
goto err_insert;
__inc_zone_page_state(page, NR_FILE_PAGES);
spin_unlock_irq(&mapping->tree_lock);
- mem_cgroup_commit_charge(page, memcg, false);
+ if (!huge)
+ mem_cgroup_commit_charge(page, memcg, false);
trace_mm_filemap_add_to_page_cache(page);
return 0;
err_insert:
page->mapping = NULL;
/* Leave page->index set: truncation relies upon it */
spin_unlock_irq(&mapping->tree_lock);
- mem_cgroup_cancel_charge(page, memcg);
+ if (!huge)
+ mem_cgroup_cancel_charge(page, memcg);
page_cache_release(page);
return error;
}
--
2.0.0

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