[PATCH v28 09/21] vfs: Cache base_acl objects in inodes

From: Andreas Gruenbacher
Date: Mon Feb 13 2017 - 10:33:38 EST

POSIX ACLs and richacls are both objects allocated by kmalloc() with a
reference count which are freed by kfree_rcu(). An inode can either
cache an access and a default POSIX ACL, or a richacl (richacls don't
have default acls). To allow an inode to cache either of the two kinds
of acls, introduce a new base_acl type and convert i_acl and
i_default_acl to that type. In most cases, the vfs doesn't care which
kind of acl an inode caches (if any).

Signed-off-by: Andreas Gruenbacher <agruenba@xxxxxxxxxx>
---
fs/9p/acl.c | 8 +++---
fs/f2fs/acl.c | 4 +--
fs/inode.c | 32 ++++++++++++++++++++--
fs/jffs2/acl.c | 6 +++--
fs/namei.c | 33 ++++++++++++-----------
fs/nfs/nfs3acl.c | 14 +++++-----
fs/posix_acl.c | 69 +++++++++++++----------------------------------
fs/richacl.c | 4 +--
include/linux/fs.h | 34 +++++++++++++++++++----
include/linux/posix_acl.h | 19 +++++++------
include/linux/richacl.h | 9 +++----
11 files changed, 128 insertions(+), 104 deletions(-)

diff --git a/fs/9p/acl.c b/fs/9p/acl.c
index b3c2cc7..0e2c114 100644
--- a/fs/9p/acl.c
+++ b/fs/9p/acl.c
@@ -87,14 +87,14 @@ int v9fs_get_acl(struct inode *inode, struct p9_fid *fid)

static struct posix_acl *v9fs_get_cached_acl(struct inode *inode, int type)
{
- struct posix_acl *acl;
+ struct base_acl *base_acl;
/*
* 9p Always cache the acl value when
* instantiating the inode (v9fs_inode_from_fid)
*/
- acl = get_cached_acl(inode, type);
- BUG_ON(is_uncached_acl(acl));
- return acl;
+ base_acl = get_cached_acl(inode, type);
+ BUG_ON(is_uncached_acl(base_acl));
+ return posix_acl(base_acl);
}

struct posix_acl *v9fs_iop_get_acl(struct inode *inode, int type)
diff --git a/fs/f2fs/acl.c b/fs/f2fs/acl.c
index 8f48769..8c8bd4e 100644
--- a/fs/f2fs/acl.c
+++ b/fs/f2fs/acl.c
@@ -266,7 +266,7 @@ static struct posix_acl *f2fs_acl_clone(const struct posix_acl *acl,
sizeof(struct posix_acl_entry);
clone = kmemdup(acl, size, flags);
if (clone)
- atomic_set(&clone->a_refcount, 1);
+ base_acl_init(&clone->a_base);
}
return clone;
}
@@ -278,8 +278,6 @@ static int f2fs_acl_create_masq(struct posix_acl *acl, umode_t *mode_p)
umode_t mode = *mode_p;
int not_equiv = 0;

- /* assert(atomic_read(acl->a_refcount) == 1); */
-
FOREACH_ACL_ENTRY(pa, acl, pe) {
switch(pa->e_tag) {
case ACL_USER_OBJ:
diff --git a/fs/inode.c b/fs/inode.c
index 88110fd..cd77ea1 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -242,14 +242,42 @@ void __destroy_inode(struct inode *inode)

#ifdef CONFIG_FS_POSIX_ACL
if (inode->i_acl && !is_uncached_acl(inode->i_acl))
- posix_acl_release(inode->i_acl);
+ base_acl_put(inode->i_acl);
if (inode->i_default_acl && !is_uncached_acl(inode->i_default_acl))
- posix_acl_release(inode->i_default_acl);
+ base_acl_put(inode->i_default_acl);
#endif
this_cpu_dec(nr_inodes);
}
EXPORT_SYMBOL(__destroy_inode);

+#ifdef CONFIG_FS_POSIX_ACL
+struct base_acl *__get_cached_acl(struct base_acl **p)
+{
+ struct base_acl *base_acl;
+
+ for (;;) {
+ rcu_read_lock();
+ base_acl = rcu_dereference(*p);
+ if (!base_acl || is_uncached_acl(base_acl) ||
+ atomic_inc_not_zero(&base_acl->ba_refcount))
+ break;
+ rcu_read_unlock();
+ cpu_relax();
+ }
+ rcu_read_unlock();
+ return base_acl;
+}
+
+void __forget_cached_acl(struct base_acl **p)
+{
+ struct base_acl *old;
+
+ old = xchg(p, ACL_NOT_CACHED);
+ if (!is_uncached_acl(old))
+ base_acl_put(old);
+}
+#endif
+
static void i_callback(struct rcu_head *head)
{
struct inode *inode = container_of(head, struct inode, i_rcu);
diff --git a/fs/jffs2/acl.c b/fs/jffs2/acl.c
index 7ebacf1..89940c4 100644
--- a/fs/jffs2/acl.c
+++ b/fs/jffs2/acl.c
@@ -291,13 +291,15 @@ int jffs2_init_acl_post(struct inode *inode)
int rc;

if (inode->i_default_acl) {
- rc = __jffs2_set_acl(inode, JFFS2_XPREFIX_ACL_DEFAULT, inode->i_default_acl);
+ rc = __jffs2_set_acl(inode, JFFS2_XPREFIX_ACL_DEFAULT,
+ posix_acl(inode->i_default_acl));
if (rc)
return rc;
}

if (inode->i_acl) {
- rc = __jffs2_set_acl(inode, JFFS2_XPREFIX_ACL_ACCESS, inode->i_acl);
+ rc = __jffs2_set_acl(inode, JFFS2_XPREFIX_ACL_ACCESS,
+ posix_acl(inode->i_acl));
if (rc)
return rc;
}
diff --git a/fs/namei.c b/fs/namei.c
index ba91d8f..4b53754 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -260,25 +260,28 @@ void putname(struct filename *name)
static int check_acl(struct inode *inode, int mask)
{
#ifdef CONFIG_FS_POSIX_ACL
- struct posix_acl *acl;
-
if (mask & MAY_NOT_BLOCK) {
- acl = get_cached_acl_rcu(inode, ACL_TYPE_ACCESS);
- if (!acl)
+ struct base_acl *base_acl;
+
+ base_acl = rcu_dereference(inode->i_acl);
+ if (!base_acl)
return -EAGAIN;
/* no ->get_acl() calls in RCU mode... */
- if (is_uncached_acl(acl))
+ if (is_uncached_acl(base_acl))
return -ECHILD;
- return posix_acl_permission(inode, acl, mask & ~MAY_NOT_BLOCK);
- }
-
- acl = get_acl(inode, ACL_TYPE_ACCESS);
- if (IS_ERR(acl))
- return PTR_ERR(acl);
- if (acl) {
- int error = posix_acl_permission(inode, acl, mask);
- posix_acl_release(acl);
- return error;
+ return posix_acl_permission(inode, posix_acl(base_acl),
+ mask & ~MAY_NOT_BLOCK);
+ } else {
+ struct posix_acl *acl;
+
+ acl = get_acl(inode, ACL_TYPE_ACCESS);
+ if (IS_ERR(acl))
+ return PTR_ERR(acl);
+ if (acl) {
+ int error = posix_acl_permission(inode, acl, mask);
+ posix_acl_release(acl);
+ return error;
+ }
}
#endif

diff --git a/fs/nfs/nfs3acl.c b/fs/nfs/nfs3acl.c
index 720d92f5..2b70944 100644
--- a/fs/nfs/nfs3acl.c
+++ b/fs/nfs/nfs3acl.c
@@ -16,28 +16,28 @@
* caching get_acl results in a race-free way. See fs/posix_acl.c:get_acl()
* for explanations.
*/
-static void nfs3_prepare_get_acl(struct posix_acl **p)
+static void nfs3_prepare_get_acl(struct base_acl **p)
{
- struct posix_acl *sentinel = uncached_acl_sentinel(current);
+ struct base_acl *sentinel = uncached_acl_sentinel(current);

if (cmpxchg(p, ACL_NOT_CACHED, sentinel) != ACL_NOT_CACHED) {
/* Not the first reader or sentinel already in place. */
}
}

-static void nfs3_complete_get_acl(struct posix_acl **p, struct posix_acl *acl)
+static void nfs3_complete_get_acl(struct base_acl **p, struct posix_acl *acl)
{
- struct posix_acl *sentinel = uncached_acl_sentinel(current);
+ struct base_acl *sentinel = uncached_acl_sentinel(current);

/* Only cache the ACL if our sentinel is still in place. */
posix_acl_dup(acl);
- if (cmpxchg(p, sentinel, acl) != sentinel)
+ if (cmpxchg(p, sentinel, &acl->a_base) != sentinel)
posix_acl_release(acl);
}

-static void nfs3_abort_get_acl(struct posix_acl **p)
+static void nfs3_abort_get_acl(struct base_acl **p)
{
- struct posix_acl *sentinel = uncached_acl_sentinel(current);
+ struct base_acl *sentinel = uncached_acl_sentinel(current);

/* Remove our sentinel upon failure. */
cmpxchg(p, sentinel, ACL_NOT_CACHED);
diff --git a/fs/posix_acl.c b/fs/posix_acl.c
index c9d48dc..5d6c5fd 100644
--- a/fs/posix_acl.c
+++ b/fs/posix_acl.c
@@ -21,7 +21,7 @@
#include <linux/export.h>
#include <linux/user_namespace.h>

-static struct posix_acl **acl_by_type(struct inode *inode, int type)
+static inline struct base_acl **acl_by_type(struct inode *inode, int type)
{
switch (type) {
case ACL_TYPE_ACCESS:
@@ -33,51 +33,23 @@ static struct posix_acl **acl_by_type(struct inode *inode, int type)
}
}

-struct posix_acl *get_cached_acl(struct inode *inode, int type)
+struct base_acl *get_cached_acl(struct inode *inode, int type)
{
- struct posix_acl **p = acl_by_type(inode, type);
- struct posix_acl *acl;
-
- for (;;) {
- rcu_read_lock();
- acl = rcu_dereference(*p);
- if (!acl || is_uncached_acl(acl) ||
- atomic_inc_not_zero(&acl->a_refcount))
- break;
- rcu_read_unlock();
- cpu_relax();
- }
- rcu_read_unlock();
- return acl;
+ return __get_cached_acl(acl_by_type(inode, type));
}
EXPORT_SYMBOL(get_cached_acl);

-struct posix_acl *get_cached_acl_rcu(struct inode *inode, int type)
-{
- return rcu_dereference(*acl_by_type(inode, type));
-}
-EXPORT_SYMBOL(get_cached_acl_rcu);
-
void set_cached_acl(struct inode *inode, int type, struct posix_acl *acl)
{
- struct posix_acl **p = acl_by_type(inode, type);
- struct posix_acl *old;
+ struct base_acl **p = acl_by_type(inode, type);
+ struct base_acl *old;

- old = xchg(p, posix_acl_dup(acl));
+ old = xchg(p, &posix_acl_dup(acl)->a_base);
if (!is_uncached_acl(old))
- posix_acl_release(old);
+ base_acl_put(old);
}
EXPORT_SYMBOL(set_cached_acl);

-static void __forget_cached_acl(struct posix_acl **p)
-{
- struct posix_acl *old;
-
- old = xchg(p, ACL_NOT_CACHED);
- if (!is_uncached_acl(old))
- posix_acl_release(old);
-}
-
void forget_cached_acl(struct inode *inode, int type)
{
__forget_cached_acl(acl_by_type(inode, type));
@@ -93,25 +65,24 @@ EXPORT_SYMBOL(forget_all_cached_acls);

struct posix_acl *get_acl(struct inode *inode, int type)
{
- void *sentinel;
- struct posix_acl **p;
+ struct base_acl **p = acl_by_type(inode, type);
+ struct base_acl *sentinel, *base_acl;
struct posix_acl *acl;

+ if (!IS_POSIXACL(inode))
+ return NULL;
+
/*
* The sentinel is used to detect when another operation like
* set_cached_acl() or forget_cached_acl() races with get_acl().
* It is guaranteed that is_uncached_acl(sentinel) is true.
*/

- acl = get_cached_acl(inode, type);
- if (!is_uncached_acl(acl))
- return acl;
-
- if (!IS_POSIXACL(inode))
- return NULL;
+ base_acl = __get_cached_acl(p);
+ if (!is_uncached_acl(base_acl))
+ return posix_acl(base_acl);

sentinel = uncached_acl_sentinel(current);
- p = acl_by_type(inode, type);

/*
* If the ACL isn't being read yet, set our sentinel. Otherwise, the
@@ -151,7 +122,7 @@ struct posix_acl *get_acl(struct inode *inode, int type)
* Cache the result, but only if our sentinel is still in place.
*/
posix_acl_dup(acl);
- if (unlikely(cmpxchg(p, sentinel, acl) != sentinel))
+ if (unlikely(cmpxchg(p, sentinel, &acl->a_base) != sentinel))
posix_acl_release(acl);
return acl;
}
@@ -163,7 +134,7 @@ EXPORT_SYMBOL(get_acl);
void
posix_acl_init(struct posix_acl *acl, int count)
{
- atomic_set(&acl->a_refcount, 1);
+ base_acl_init(&acl->a_base);
acl->a_count = count;
}
EXPORT_SYMBOL(posix_acl_init);
@@ -196,7 +167,7 @@ posix_acl_clone(const struct posix_acl *acl, gfp_t flags)
sizeof(struct posix_acl_entry);
clone = kmemdup(acl, size, flags);
if (clone)
- atomic_set(&clone->a_refcount, 1);
+ base_acl_init(&clone->a_base);
}
return clone;
}
@@ -418,8 +389,6 @@ static int posix_acl_create_masq(struct posix_acl *acl, umode_t *mode_p)
umode_t mode = *mode_p;
int not_equiv = 0;

- /* assert(atomic_read(acl->a_refcount) == 1); */
-
FOREACH_ACL_ENTRY(pa, acl, pe) {
switch(pa->e_tag) {
case ACL_USER_OBJ:
@@ -473,8 +442,6 @@ static int __posix_acl_chmod_masq(struct posix_acl *acl, umode_t mode)
struct posix_acl_entry *group_obj = NULL, *mask_obj = NULL;
struct posix_acl_entry *pa, *pe;

- /* assert(atomic_read(acl->a_refcount) == 1); */
-
FOREACH_ACL_ENTRY(pa, acl, pe) {
switch(pa->e_tag) {
case ACL_USER_OBJ:
diff --git a/fs/richacl.c b/fs/richacl.c
index 0443090..57a4048 100644
--- a/fs/richacl.c
+++ b/fs/richacl.c
@@ -31,7 +31,7 @@ richacl_alloc(int count, gfp_t gfp)
struct richacl *acl = kzalloc(size, gfp);

if (acl) {
- atomic_set(&acl->a_refcount, 1);
+ base_acl_init(&acl->a_base);
acl->a_count = count;
}
return acl;
@@ -50,7 +50,7 @@ richacl_clone(const struct richacl *acl, gfp_t gfp)

if (dup) {
memcpy(dup, acl, size);
- atomic_set(&dup->a_refcount, 1);
+ base_acl_init(&dup->a_base);
}
return dup;
}
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 3de40d3..b33823c 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -530,18 +530,22 @@ static inline void mapping_allow_writable(struct address_space *mapping)
#define i_size_ordered_init(inode) do { } while (0)
#endif

+struct base_acl {
+ atomic_t ba_refcount;
+ struct rcu_head ba_rcu;
+};
struct posix_acl;
#define ACL_NOT_CACHED ((void *)(-1))
#define ACL_DONT_CACHE ((void *)(-3))

-static inline struct posix_acl *
+static inline struct base_acl *
uncached_acl_sentinel(struct task_struct *task)
{
return (void *)task + 1;
}

static inline bool
-is_uncached_acl(struct posix_acl *acl)
+is_uncached_acl(struct base_acl *acl)
{
return (long)acl & 1;
}
@@ -564,9 +568,9 @@ struct inode {
kgid_t i_gid;
unsigned int i_flags;

-#ifdef CONFIG_FS_POSIX_ACL
- struct posix_acl *i_acl;
- struct posix_acl *i_default_acl;
+#if defined(CONFIG_FS_POSIX_ACL)
+ struct base_acl *i_acl;
+ struct base_acl *i_default_acl;
#endif

const struct inode_operations *i_op;
@@ -3184,4 +3188,24 @@ static inline bool dir_relax_shared(struct inode *inode)
extern bool path_noexec(const struct path *path);
extern void inode_nohighmem(struct inode *inode);

+static inline void base_acl_get(struct base_acl *acl)
+{
+ if (acl)
+ atomic_inc(&acl->ba_refcount);
+}
+
+static inline void base_acl_put(struct base_acl *acl)
+{
+ if (acl && atomic_dec_and_test(&acl->ba_refcount))
+ kfree_rcu(acl, ba_rcu);
+}
+
+static inline void base_acl_init(struct base_acl *acl)
+{
+ atomic_set(&acl->ba_refcount, 1);
+}
+
+extern struct base_acl *__get_cached_acl(struct base_acl **);
+extern void __forget_cached_acl(struct base_acl **);
+
#endif /* _LINUX_FS_H */
diff --git a/include/linux/posix_acl.h b/include/linux/posix_acl.h
index 5a9a739..abfb786 100644
--- a/include/linux/posix_acl.h
+++ b/include/linux/posix_acl.h
@@ -23,8 +23,7 @@ struct posix_acl_entry {
};

struct posix_acl {
- atomic_t a_refcount;
- struct rcu_head a_rcu;
+ struct base_acl a_base; /* must be first, see posix_acl_release() */
unsigned int a_count;
struct posix_acl_entry a_entries[0];
};
@@ -39,8 +38,7 @@ struct posix_acl {
static inline struct posix_acl *
posix_acl_dup(struct posix_acl *acl)
{
- if (acl)
- atomic_inc(&acl->a_refcount);
+ base_acl_get(&acl->a_base);
return acl;
}

@@ -50,10 +48,16 @@ posix_acl_dup(struct posix_acl *acl)
static inline void
posix_acl_release(struct posix_acl *acl)
{
- if (acl && atomic_dec_and_test(&acl->a_refcount))
- kfree_rcu(acl, a_rcu);
+ BUILD_BUG_ON(offsetof(struct posix_acl, a_base) != 0);
+ base_acl_put(&acl->a_base);
}

+static inline struct posix_acl *
+posix_acl(struct base_acl *base_acl)
+{
+ BUILD_BUG_ON(offsetof(struct posix_acl, a_base) != 0);
+ return container_of(base_acl, struct posix_acl, a_base);
+}

/* posix_acl.c */

@@ -78,8 +82,7 @@ extern int posix_acl_update_mode(struct inode *, umode_t *, struct posix_acl **)
extern int simple_set_acl(struct inode *, struct posix_acl *, int);
extern int simple_acl_create(struct inode *, struct inode *);

-struct posix_acl *get_cached_acl(struct inode *inode, int type);
-struct posix_acl *get_cached_acl_rcu(struct inode *inode, int type);
+struct base_acl *get_cached_acl(struct inode *inode, int type);
void set_cached_acl(struct inode *inode, int type, struct posix_acl *acl);
void forget_cached_acl(struct inode *inode, int type);
void forget_all_cached_acls(struct inode *inode);
diff --git a/include/linux/richacl.h b/include/linux/richacl.h
index 700888b..d535206 100644
--- a/include/linux/richacl.h
+++ b/include/linux/richacl.h
@@ -31,7 +31,7 @@ struct richace {
};

struct richacl {
- atomic_t a_refcount;
+ struct base_acl a_base; /* must be first, see richacl_put() */
unsigned int a_owner_mask;
unsigned int a_group_mask;
unsigned int a_other_mask;
@@ -56,8 +56,7 @@ struct richacl {
static inline struct richacl *
richacl_get(struct richacl *acl)
{
- if (acl)
- atomic_inc(&acl->a_refcount);
+ base_acl_get(&acl->a_base);
return acl;
}

@@ -67,8 +66,8 @@ richacl_get(struct richacl *acl)
static inline void
richacl_put(struct richacl *acl)
{
- if (acl && atomic_dec_and_test(&acl->a_refcount))
- kfree(acl);
+ BUILD_BUG_ON(offsetof(struct richacl, a_base) != 0);
+ base_acl_put(&acl->a_base);
}

/**
--
2.7.4