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Subject[RFC 26/43] mm: shmem: when inserting, handle pages already charged to a memcg
Date
If shmem_insert_page() is called to insert a page that was preserved
using PKRAM on the current boot (i.e. preserved page is restored without
an intervening kexec boot), the page will still be charged to a memory
cgroup because it is never freed. Don't try to charge it again.

Signed-off-by: Anthony Yznaga <anthony.yznaga@oracle.com>
---
mm/shmem.c | 21 +++++++++++++--------
1 file changed, 13 insertions(+), 8 deletions(-)

diff --git a/mm/shmem.c b/mm/shmem.c
index 13475073fb52..1f3b43b8fa34 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -693,6 +693,7 @@ int shmem_insert_page(struct mm_struct *mm, struct inode *inode, pgoff_t index,
struct mem_cgroup *memcg;
pgoff_t hindex = index;
bool on_lru = PageLRU(page);
+ bool has_memcg = page->mem_cgroup ? true : false;

if (index > (MAX_LFS_FILESIZE >> PAGE_SHIFT))
return -EFBIG;
@@ -738,20 +739,24 @@ int shmem_insert_page(struct mm_struct *mm, struct inode *inode, pgoff_t index,

__SetPageReferenced(page);

- err = mem_cgroup_try_charge_delay(page, mm, gfp, &memcg,
- PageTransHuge(page));
- if (err)
- goto out_unlock;
+ if (!has_memcg) {
+ err = mem_cgroup_try_charge_delay(page, mm, gfp, &memcg,
+ PageTransHuge(page));
+ if (err)
+ goto out_unlock;
+ }

err = shmem_add_to_page_cache(page, mapping, hindex,
NULL, gfp & GFP_RECLAIM_MASK);
if (err) {
- mem_cgroup_cancel_charge(page, memcg,
- PageTransHuge(page));
+ if (!has_memcg)
+ mem_cgroup_cancel_charge(page, memcg,
+ PageTransHuge(page));
goto out_unlock;
}
- mem_cgroup_commit_charge(page, memcg, on_lru,
- PageTransHuge(page));
+ if (!has_memcg)
+ mem_cgroup_commit_charge(page, memcg, on_lru,
+ PageTransHuge(page));

if (!on_lru)
lru_cache_add_anon(page);
--
2.13.3
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