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Message-id: <164876616694.25542.14010655277238655246@noble.neil.brown.name>
Date: Fri, 01 Apr 2022 09:36:06 +1100
From: "NeilBrown" <neilb@...e.de>
To: "Muchun Song" <songmuchun@...edance.com>
Cc: "Andrew Morton" <akpm@...ux-foundation.org>,
"Matthew Wilcox" <willy@...radead.org>,
"Johannes Weiner" <hannes@...xchg.org>,
"Michal Hocko" <mhocko@...nel.org>,
"Vladimir Davydov" <vdavydov.dev@...il.com>,
"Shakeel Butt" <shakeelb@...gle.com>,
"Roman Gushchin" <roman.gushchin@...ux.dev>,
"Yang Shi" <shy828301@...il.com>, "Alex Shi" <alexs@...nel.org>,
"Wei Yang" <richard.weiyang@...il.com>,
"Dave Chinner" <david@...morbit.com>,
trond.myklebust@...merspace.com, anna.schumaker@...app.com,
jaegeuk@...nel.org, chao@...nel.org,
"Kari Argillander" <kari.argillander@...il.com>,
"Vlastimil Babka" <vbabka@...e.cz>,
"linux-fsdevel" <linux-fsdevel@...r.kernel.org>,
"LKML" <linux-kernel@...r.kernel.org>,
"Linux Memory Management List" <linux-mm@...ck.org>,
linux-nfs@...r.kernel.org, "Qi Zheng" <zhengqi.arch@...edance.com>,
"Xiongchun duan" <duanxiongchun@...edance.com>,
"Fam Zheng" <fam.zheng@...edance.com>,
"Muchun Song" <smuchun@...il.com>
Subject: Re: [PATCH v6 12/16] mm: list_lru: replace linear array with xarray
On Thu, 31 Mar 2022, Muchun Song wrote:
>
> Thanks for your report. I knew the reason. It is because the following
> patch in this series was missed upstream. Could you help me test if it
> works properly?
>
> [v6,06/16] nfs42: use a specific kmem_cache to allocate nfs4_xattr_entry
>
Thanks for the quick response! That patch helps, but has a bug. My
testing resulted in refcount underflow errors.
Problem is that kref_init() is called in nfs4_xattr_entry_init_once().
This means that it is initialised to '1' the first time an entry is
allocated, but it is left as zero the second time.
I applied:
--- a/fs/nfs/nfs42xattr.c
+++ b/fs/nfs/nfs42xattr.c
@@ -191,6 +191,7 @@ nfs4_xattr_alloc_entry(const char *name, const void *value,
entry = kmem_cache_alloc_lru(nfs4_xattr_entry_cachep, lru, gfp);
if (!entry)
return NULL;
+ kref_init(&entry->ref);
namep = kstrdup_const(name, gfp);
if (!namep && name)
goto free_buf;
@@ -974,7 +975,6 @@ static void nfs4_xattr_entry_init_once(void *p)
{
struct nfs4_xattr_entry *entry = p;
- kref_init(&entry->ref);
entry->bucket = NULL;
INIT_LIST_HEAD(&entry->lru);
INIT_LIST_HEAD(&entry->dispose);
and now it seems to work.
The complete patch that I applied is below. I haven't reviewed it, just
tested it.
Tested-by: NeilBrown <neilb@...e.de>
Thanks,
NeilBrown
From: Muchun Song <songmuchun@...edance.com>
Date: Mon, 28 Feb 2022 20:21:16 +0800
Subject: [PATCH] nfs42: use a specific kmem_cache to allocate nfs4_xattr_entry
If we want to add the allocated objects to its list_lru, we should use
kmem_cache_alloc_lru() to allocate objects. So intruduce
nfs4_xattr_entry_cachep which is used to allocate nfs4_xattr_entry.
Signed-off-by: Muchun Song <songmuchun@...edance.com>
diff --git a/fs/nfs/nfs42xattr.c b/fs/nfs/nfs42xattr.c
index ad3405c64b9e..d4163c46acf1 100644
--- a/fs/nfs/nfs42xattr.c
+++ b/fs/nfs/nfs42xattr.c
@@ -81,7 +81,7 @@ struct nfs4_xattr_entry {
struct hlist_node hnode;
struct list_head lru;
struct list_head dispose;
- char *xattr_name;
+ const char *xattr_name;
void *xattr_value;
size_t xattr_size;
struct nfs4_xattr_bucket *bucket;
@@ -98,6 +98,7 @@ static struct list_lru nfs4_xattr_entry_lru;
static struct list_lru nfs4_xattr_large_entry_lru;
static struct kmem_cache *nfs4_xattr_cache_cachep;
+static struct kmem_cache *nfs4_xattr_entry_cachep;
/*
* Hashing helper functions.
@@ -177,49 +178,28 @@ nfs4_xattr_alloc_entry(const char *name, const void *value,
{
struct nfs4_xattr_entry *entry;
void *valp;
- char *namep;
- size_t alloclen, slen;
- char *buf;
- uint32_t flags;
+ const char *namep;
+ uint32_t flags = len > PAGE_SIZE ? NFS4_XATTR_ENTRY_EXTVAL : 0;
+ gfp_t gfp = GFP_KERNEL;
+ struct list_lru *lru;
BUILD_BUG_ON(sizeof(struct nfs4_xattr_entry) +
XATTR_NAME_MAX + 1 > PAGE_SIZE);
- alloclen = sizeof(struct nfs4_xattr_entry);
- if (name != NULL) {
- slen = strlen(name) + 1;
- alloclen += slen;
- } else
- slen = 0;
-
- if (alloclen + len <= PAGE_SIZE) {
- alloclen += len;
- flags = 0;
- } else {
- flags = NFS4_XATTR_ENTRY_EXTVAL;
- }
-
- buf = kmalloc(alloclen, GFP_KERNEL);
- if (buf == NULL)
+ lru = flags & NFS4_XATTR_ENTRY_EXTVAL ? &nfs4_xattr_large_entry_lru :
+ &nfs4_xattr_entry_lru;
+ entry = kmem_cache_alloc_lru(nfs4_xattr_entry_cachep, lru, gfp);
+ if (!entry)
return NULL;
- entry = (struct nfs4_xattr_entry *)buf;
-
- if (name != NULL) {
- namep = buf + sizeof(struct nfs4_xattr_entry);
- memcpy(namep, name, slen);
- } else {
- namep = NULL;
- }
-
-
- if (flags & NFS4_XATTR_ENTRY_EXTVAL) {
- valp = kvmalloc(len, GFP_KERNEL);
- if (valp == NULL) {
- kfree(buf);
- return NULL;
- }
- } else if (len != 0) {
- valp = buf + sizeof(struct nfs4_xattr_entry) + slen;
+ kref_init(&entry->ref);
+ namep = kstrdup_const(name, gfp);
+ if (!namep && name)
+ goto free_buf;
+
+ if (len != 0) {
+ valp = kvmalloc(len, gfp);
+ if (!valp)
+ goto free_name;
} else
valp = NULL;
@@ -232,23 +212,23 @@ nfs4_xattr_alloc_entry(const char *name, const void *value,
entry->flags = flags;
entry->xattr_value = valp;
- kref_init(&entry->ref);
entry->xattr_name = namep;
entry->xattr_size = len;
- entry->bucket = NULL;
- INIT_LIST_HEAD(&entry->lru);
- INIT_LIST_HEAD(&entry->dispose);
- INIT_HLIST_NODE(&entry->hnode);
return entry;
+free_name:
+ kfree_const(namep);
+free_buf:
+ kmem_cache_free(nfs4_xattr_entry_cachep, entry);
+ return NULL;
}
static void
nfs4_xattr_free_entry(struct nfs4_xattr_entry *entry)
{
- if (entry->flags & NFS4_XATTR_ENTRY_EXTVAL)
- kvfree(entry->xattr_value);
- kfree(entry);
+ kvfree(entry->xattr_value);
+ kfree_const(entry->xattr_name);
+ kmem_cache_free(nfs4_xattr_entry_cachep, entry);
}
static void
@@ -289,7 +269,7 @@ nfs4_xattr_alloc_cache(void)
{
struct nfs4_xattr_cache *cache;
- cache = kmem_cache_alloc(nfs4_xattr_cache_cachep, GFP_KERNEL);
+ cache = kmem_cache_alloc_lru(nfs4_xattr_cache_cachep, &nfs4_xattr_cache_lru, GFP_KERNEL);
if (cache == NULL)
return NULL;
@@ -991,6 +971,16 @@ static void nfs4_xattr_cache_init_once(void *p)
INIT_LIST_HEAD(&cache->dispose);
}
+static void nfs4_xattr_entry_init_once(void *p)
+{
+ struct nfs4_xattr_entry *entry = p;
+
+ entry->bucket = NULL;
+ INIT_LIST_HEAD(&entry->lru);
+ INIT_LIST_HEAD(&entry->dispose);
+ INIT_HLIST_NODE(&entry->hnode);
+}
+
int __init nfs4_xattr_cache_init(void)
{
int ret = 0;
@@ -1002,6 +992,13 @@ int __init nfs4_xattr_cache_init(void)
if (nfs4_xattr_cache_cachep == NULL)
return -ENOMEM;
+ nfs4_xattr_entry_cachep = kmem_cache_create("nfs4_xattr_entry",
+ sizeof(struct nfs4_xattr_entry), 0,
+ (SLAB_RECLAIM_ACCOUNT | SLAB_MEM_SPREAD | SLAB_ACCOUNT),
+ nfs4_xattr_entry_init_once);
+ if (!nfs4_xattr_entry_cachep)
+ goto out5;
+
ret = list_lru_init_memcg(&nfs4_xattr_large_entry_lru,
&nfs4_xattr_large_entry_shrinker);
if (ret)
@@ -1039,6 +1036,8 @@ int __init nfs4_xattr_cache_init(void)
out3:
list_lru_destroy(&nfs4_xattr_large_entry_lru);
out4:
+ kmem_cache_destroy(nfs4_xattr_entry_cachep);
+out5:
kmem_cache_destroy(nfs4_xattr_cache_cachep);
return ret;
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