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Subject[PATCH] dcache: fix indirectly reclaimable memory accounting
Date
External names can be released using kfree_rcu()
from release_dentry_name_snapshot() and copy_name(),
and it will lead to the imbalance in the indirectly
reclaimable memory accounting.

Fix this by introducing __d_free_external_name() and
call it from all release paths.

Signed-off-by: Roman Gushchin <guro@fb.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: linux-fsdevel@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: linux-mm@kvack.org
Cc: kernel-team@fb.com
---
fs/dcache.c | 18 +++++++++++++-----
1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/fs/dcache.c b/fs/dcache.c
index 98826efe22a0..9008057a7460 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -266,16 +266,24 @@ static void __d_free(struct rcu_head *head)
kmem_cache_free(dentry_cache, dentry);
}

-static void __d_free_external(struct rcu_head *head)
+static void __d_free_external_name(struct rcu_head *head)
{
- struct dentry *dentry = container_of(head, struct dentry, d_u.d_rcu);
- struct external_name *name = external_name(dentry);
+ struct external_name *name = container_of(head, struct external_name,
+ u.head);

mod_node_page_state(page_pgdat(virt_to_page(name)),
NR_INDIRECTLY_RECLAIMABLE_BYTES,
-ksize(name));

kfree(name);
+}
+
+static void __d_free_external(struct rcu_head *head)
+{
+ struct dentry *dentry = container_of(head, struct dentry, d_u.d_rcu);
+
+ __d_free_external_name(&external_name(dentry)->u.head);
+
kmem_cache_free(dentry_cache, dentry);
}

@@ -307,7 +315,7 @@ void release_dentry_name_snapshot(struct name_snapshot *name)
struct external_name *p;
p = container_of(name->name, struct external_name, name[0]);
if (unlikely(atomic_dec_and_test(&p->u.count)))
- kfree_rcu(p, u.head);
+ call_rcu(&p->u.head, __d_free_external_name);
}
}
EXPORT_SYMBOL(release_dentry_name_snapshot);
@@ -2769,7 +2777,7 @@ static void copy_name(struct dentry *dentry, struct dentry *target)
dentry->d_name.hash_len = target->d_name.hash_len;
}
if (old_name && likely(atomic_dec_and_test(&old_name->u.count)))
- kfree_rcu(old_name, u.head);
+ call_rcu(&old_name->u.head, __d_free_external_name);
}

static void dentry_lock_for_move(struct dentry *dentry, struct dentry *target)
--
2.14.3
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