The patch titled
Subject: mm: memcontrol: rewrite charge API: fix shmem_unuse
has been added to the -mm tree. Its filename is
mm-memcontrol-rewrite-charge-api-fix-shmem_unuse.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-memcontrol-rewrite-charge-api-fix-shmem_unuse.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-memcontrol-rewrite-charge-api-fix-shmem_unuse.patch
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------------------------------------------------------
From: Hugh Dickins <hughd@xxxxxxxxxx>
Subject: mm: memcontrol: rewrite charge API: fix shmem_unuse
Under shmem swapping and swapoff load, I sometimes hit the
VM_BUG_ON_PAGE(!page->mapping) in mem_cgroup_commit_charge() at
mm/memcontrol.c:6502! Each time it has been a call from shmem_unuse().
Yes, there are some cases (most commonly when the page being unswapped is
in a file being unlinked and evicted at that time) when the charge should
not be committed. In the old scheme, the page got uncharged again on
release; but in the new scheme, it hits that BUG beforehand.
It's a useful BUG, so adapt shmem_unuse() to allow for it. Which needs
more info from shmem_unuse_inode(): so abuse -EAGAIN internally to replace
the previous !found state (-ENOENT would be a more natural code, but
that's exactly what you get when the swap has been evicted).
Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/shmem.c | 14 +++++++-------
1 file changed, 7 insertions(+), 7 deletions(-)
diff -puN mm/shmem.c~mm-memcontrol-rewrite-charge-api-fix-shmem_unuse mm/shmem.c
--- a/mm/shmem.c~mm-memcontrol-rewrite-charge-api-fix-shmem_unuse
+++ a/mm/shmem.c
@@ -594,7 +594,7 @@ static int shmem_unuse_inode(struct shme
radswap = swp_to_radix_entry(swap);
index = radix_tree_locate_item(&mapping->page_tree, radswap);
if (index == -1)
- return 0;
+ return -EAGAIN;
/*
* Move _head_ to start search for next from here.
@@ -653,7 +653,6 @@ static int shmem_unuse_inode(struct shme
spin_unlock(&info->lock);
swap_free(swap);
}
- error = 1; /* not an error, but entry was found */
}
return error;
}
@@ -666,7 +665,6 @@ int shmem_unuse(swp_entry_t swap, struct
struct list_head *this, *next;
struct shmem_inode_info *info;
struct mem_cgroup *memcg;
- int found = 0;
int error = 0;
/*
@@ -685,22 +683,24 @@ int shmem_unuse(swp_entry_t swap, struct
if (error)
goto out;
/* No radix_tree_preload: swap entry keeps a place for page in tree */
+ error = -EAGAIN;
mutex_lock(&shmem_swaplist_mutex);
list_for_each_safe(this, next, &shmem_swaplist) {
info = list_entry(this, struct shmem_inode_info, swaplist);
if (info->swapped)
- found = shmem_unuse_inode(info, swap, &page);
+ error = shmem_unuse_inode(info, swap, &page);
else
list_del_init(&info->swaplist);
cond_resched();
- if (found)
+ if (error != -EAGAIN)
break;
}
mutex_unlock(&shmem_swaplist_mutex);
- if (found < 0) {
- error = found;
+ if (error) {
+ if (error != -ENOMEM)
+ error = 0;
mem_cgroup_cancel_charge(page, memcg);
} else
mem_cgroup_commit_charge(page, memcg, true);
_
Patches currently in -mm which might be from hughd@xxxxxxxxxx are
shmem-fix-init_page_accessed-use-to-stop-pagelru-bug.patch
mm-memoryc-use-entry-=-access_oncepte-in-handle_pte_fault.patch
mm-memcontrol-fold-mem_cgroup_do_charge.patch
mm-memcontrol-rearrange-charging-fast-path.patch
mm-memcontrol-reclaim-at-least-once-for-__gfp_noretry.patch
mm-huge_memory-use-gfp_transhuge-when-charging-huge-pages.patch
mm-memcontrol-retry-reclaim-for-oom-disabled-and-__gfp_nofail-charges.patch
mm-memcontrol-remove-explicit-oom-parameter-in-charge-path.patch
mm-memcontrol-simplify-move-precharge-function.patch
mm-memcontrol-catch-root-bypass-in-move-precharge.patch
mm-memcontrol-use-root_mem_cgroup-res_counter.patch
mm-memcontrol-remove-ordering-between-pc-mem_cgroup-and-pagecgroupused.patch
mm-memcontrol-do-not-acquire-page_cgroup-lock-for-kmem-pages.patch
mm-memcontrol-rewrite-charge-api.patch
mm-memcontrol-rewrite-uncharge-api.patch
mm-memcontrol-rewrite-uncharge-api-fix-5.patch
mm-memcontrol-rewrite-charge-api-fix-shmem_unuse.patch
mm-vmallocc-add-a-schedule-point-to-vmalloc.patch
mm-vmallocc-add-a-schedule-point-to-vmalloc-fix.patch
include-linux-mmdebugh-add-vm_warn_once.patch
shmem-fix-double-uncharge-in-__shmem_file_setup.patch
shmem-update-memory-reservation-on-truncate.patch
mm-catch-memory-commitment-underflow.patch
mm-catch-memory-commitment-underflow-fix.patch
mm-export-nr_shmem-via-sysinfo2-si_meminfo-interfaces.patch
mm-replace-init_page_accessed-by-__setpagereferenced.patch
mm-zbud-zbud_alloc-minor-param-change.patch
mm-zbud-change-zbud_alloc-size-type-to-size_t.patch
mm-zpool-implement-common-zpool-api-to-zbud-zsmalloc.patch
mm-zpool-zbud-zsmalloc-implement-zpool.patch
mm-zpool-update-zswap-to-use-zpool.patch
mm-zpool-prevent-zbud-zsmalloc-from-unloading-when-used.patch
list-use-argument-hlist_add_after-names-from-rcu-variant.patch
list-fix-order-of-arguments-for-hlist_add_after_rcu.patch
klist-use-same-naming-scheme-as-hlist-for-klist_add_after.patch
mm-replace-remap_file_pages-syscall-with-emulation-fix-3.patch
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