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Subject[PATCH] dcache: fix indirectly reclaimable memory accounting for CONFIG_SLOB
Date
Indirectly reclaimable memory accounting uses
kmalloc_size()/kmalloc_index() functions to estimate
amount of consumed memory. kmalloc_size() always returns 0
and kmalloc_index() is not defined for CONFIG_SLOB,
and so it breaks the build.

Fix this by using ksize() function instead.

Slub:
$ cat /proc/meminfo | grep Avail
MemAvailable: 7857112 kB
$ python indirect.py
$ cat /proc/meminfo | grep Avail
MemAvailable: 7781312 kB

Slob:
$ cat /proc/meminfo | grep Avail
MemAvailable: 7853272 kB
$ python indirect.py
$ cat /proc/meminfo | grep Avail
MemAvailable: 7616644 kB

indirect.py:
import os

for iter in range (0, 1000000):
try:
name = ("/some_long_name_%d" % iter) + "_" * 220
os.stat(name)
except Exception:
pass

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: Tony Lindgren <tony@atomide.com>
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 | 26 ++++++++++----------------
1 file changed, 10 insertions(+), 16 deletions(-)

diff --git a/fs/dcache.c b/fs/dcache.c
index 135297a2d40e..98826efe22a0 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -270,12 +270,10 @@ static void __d_free_external(struct rcu_head *head)
{
struct dentry *dentry = container_of(head, struct dentry, d_u.d_rcu);
struct external_name *name = external_name(dentry);
- unsigned long bytes;

- bytes = dentry->d_name.len + offsetof(struct external_name, name[1]);
mod_node_page_state(page_pgdat(virt_to_page(name)),
NR_INDIRECTLY_RECLAIMABLE_BYTES,
- -kmalloc_size(kmalloc_index(bytes)));
+ -ksize(name));

kfree(name);
kmem_cache_free(dentry_cache, dentry);
@@ -1607,10 +1605,10 @@ EXPORT_SYMBOL(d_invalidate);

struct dentry *__d_alloc(struct super_block *sb, const struct qstr *name)
{
+ struct external_name *ext = NULL;
struct dentry *dentry;
char *dname;
int err;
- size_t reclaimable = 0;

dentry = kmem_cache_alloc(dentry_cache, GFP_KERNEL);
if (!dentry)
@@ -1627,17 +1625,15 @@ struct dentry *__d_alloc(struct super_block *sb, const struct qstr *name)
name = &slash_name;
dname = dentry->d_iname;
} else if (name->len > DNAME_INLINE_LEN-1) {
- struct external_name *p;
+ size_t size = offsetof(struct external_name, name[1]);

- reclaimable = offsetof(struct external_name, name[1]) +
- name->len;
- p = kmalloc(reclaimable, GFP_KERNEL_ACCOUNT);
- if (!p) {
+ ext = kmalloc(size + name->len, GFP_KERNEL_ACCOUNT);
+ if (!ext) {
kmem_cache_free(dentry_cache, dentry);
return NULL;
}
- atomic_set(&p->u.count, 1);
- dname = p->name;
+ atomic_set(&ext->u.count, 1);
+ dname = ext->name;
} else {
dname = dentry->d_iname;
}
@@ -1676,12 +1672,10 @@ struct dentry *__d_alloc(struct super_block *sb, const struct qstr *name)
}
}

- if (unlikely(reclaimable)) {
- pg_data_t *pgdat;
-
- pgdat = page_pgdat(virt_to_page(external_name(dentry)));
+ if (unlikely(ext)) {
+ pg_data_t *pgdat = page_pgdat(virt_to_page(ext));
mod_node_page_state(pgdat, NR_INDIRECTLY_RECLAIMABLE_BYTES,
- kmalloc_size(kmalloc_index(reclaimable)));
+ ksize(ext));
}

this_cpu_inc(nr_dentry);
--
2.14.3
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