Re: [PATCH v14 11/22] vfs: Cache base_acl objects in inodes

From: Andreas Dilger
Date: Sun Nov 08 2015 - 03:05:29 EST

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On Nov 5, 2015, at 4:39 AM, Andreas Gruenbacher <agruenba@xxxxxxxxxx> wrote:
>
> 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 do not
> 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 then doesn't care which
> kind of acl an inode caches (if any).
>
> Signed-off-by: Andreas Gruenbacher <agruenba@xxxxxxxxxx>

Reviewed-by: Andreas Dilger <adilger@xxxxxxxxx>

> ---
> drivers/staging/lustre/lustre/llite/llite_lib.c | 2 +-
> fs/f2fs/acl.c | 4 +--
> fs/inode.c | 4 +--
> fs/jffs2/acl.c | 10 ++++--
> fs/posix_acl.c | 41 +++++++++++++------------
> fs/richacl_base.c | 4 +--
> include/linux/fs.h | 34 ++++++++++++++++++--
> include/linux/posix_acl.h | 12 +++-----
> include/linux/richacl.h | 9 +++---
> 9 files changed, 75 insertions(+), 45 deletions(-)
>
> diff --git a/drivers/staging/lustre/lustre/llite/llite_lib.c b/drivers/staging/lustre/lustre/llite/llite_lib.c
> index b4ed6c8..46912c2 100644
> --- a/drivers/staging/lustre/lustre/llite/llite_lib.c
> +++ b/drivers/staging/lustre/lustre/llite/llite_lib.c
> @@ -1118,7 +1118,7 @@ void ll_clear_inode(struct inode *inode)
> }
> #ifdef CONFIG_FS_POSIX_ACL
> else if (lli->lli_posix_acl) {
> - LASSERT(atomic_read(&lli->lli_posix_acl->a_refcount) == 1);
> + LASSERT(base_acl_refcount(&lli->lli_posix_acl->a_base) == 1);
> LASSERT(lli->lli_remote_perms == NULL);
> posix_acl_release(lli->lli_posix_acl);
> lli->lli_posix_acl = NULL;
> diff --git a/fs/f2fs/acl.c b/fs/f2fs/acl.c
> index c8f25f7..9646197 100644
> --- a/fs/f2fs/acl.c
> +++ b/fs/f2fs/acl.c
> @@ -270,7 +270,7 @@ 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;
> }
> @@ -282,7 +282,7 @@ 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); */
> + /* assert(base_acl_refcount(&acl->a_base) == 1); */
>
> FOREACH_ACL_ENTRY(pa, acl, pe) {
> switch(pa->e_tag) {
> diff --git a/fs/inode.c b/fs/inode.c
> index 78a17b8..5c46ae5 100644
> --- a/fs/inode.c
> +++ b/fs/inode.c
> @@ -233,9 +233,9 @@ void __destroy_inode(struct inode *inode)
>
> #ifdef CONFIG_FS_POSIX_ACL
> if (inode->i_acl && inode->i_acl != ACL_NOT_CACHED)
> - posix_acl_release(inode->i_acl);
> + base_acl_put(inode->i_acl);
> if (inode->i_default_acl && inode->i_default_acl != ACL_NOT_CACHED)
> - posix_acl_release(inode->i_default_acl);
> + base_acl_put(inode->i_default_acl);
> #endif
> this_cpu_dec(nr_inodes);
> }
> diff --git a/fs/jffs2/acl.c b/fs/jffs2/acl.c
> index 2f7a3c0..569cb1b 100644
> --- a/fs/jffs2/acl.c
> +++ b/fs/jffs2/acl.c
> @@ -294,13 +294,19 @@ 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);
> + struct posix_acl *default_acl = container_of(
> + inode->i_default_acl, struct posix_acl, a_base);
> +
> + rc = __jffs2_set_acl(inode, JFFS2_XPREFIX_ACL_DEFAULT, default_acl);
> if (rc)
> return rc;
> }
>
> if (inode->i_acl) {
> - rc = __jffs2_set_acl(inode, JFFS2_XPREFIX_ACL_ACCESS, inode->i_acl);
> + struct posix_acl *acl = container_of(
> + inode->i_acl, struct posix_acl, a_base);
> +
> + rc = __jffs2_set_acl(inode, JFFS2_XPREFIX_ACL_ACCESS, acl);
> if (rc)
> return rc;
> }
> diff --git a/fs/posix_acl.c b/fs/posix_acl.c
> index aacfb58..4573315 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 struct base_acl **acl_by_type(struct inode *inode, int type)
> {
> switch (type) {
> case ACL_TYPE_ACCESS:
> @@ -35,63 +35,64 @@ static struct posix_acl **acl_by_type(struct inode *inode, int type)
>
> struct posix_acl *get_cached_acl(struct inode *inode, int type)
> {
> - struct posix_acl **p = acl_by_type(inode, type);
> - struct posix_acl *acl = ACCESS_ONCE(*p);
> + struct base_acl **p = acl_by_type(inode, type);
> + struct base_acl *acl = ACCESS_ONCE(*p);
> if (acl) {
> spin_lock(&inode->i_lock);
> acl = *p;
> if (acl != ACL_NOT_CACHED)
> - acl = posix_acl_dup(acl);
> + base_acl_get(acl);
> spin_unlock(&inode->i_lock);
> }
> - return acl;
> + return container_of(acl, struct posix_acl, a_base);
> }
> 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));
> + struct base_acl *acl = rcu_dereference(*acl_by_type(inode, type));
> + return container_of(acl, struct posix_acl, a_base);
> }
> 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;
> spin_lock(&inode->i_lock);
> old = *p;
> - rcu_assign_pointer(*p, posix_acl_dup(acl));
> + rcu_assign_pointer(*p, &posix_acl_dup(acl)->a_base);
> spin_unlock(&inode->i_lock);
> if (old != ACL_NOT_CACHED)
> - posix_acl_release(old);
> + base_acl_put(old);
> }
> EXPORT_SYMBOL(set_cached_acl);
>
> void forget_cached_acl(struct inode *inode, int type)
> {
> - 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;
> spin_lock(&inode->i_lock);
> old = *p;
> *p = ACL_NOT_CACHED;
> spin_unlock(&inode->i_lock);
> if (old != ACL_NOT_CACHED)
> - posix_acl_release(old);
> + base_acl_put(old);
> }
> EXPORT_SYMBOL(forget_cached_acl);
>
> void forget_all_cached_acls(struct inode *inode)
> {
> - struct posix_acl *old_access, *old_default;
> + struct base_acl *old_access, *old_default;
> spin_lock(&inode->i_lock);
> old_access = inode->i_acl;
> old_default = inode->i_default_acl;
> inode->i_acl = inode->i_default_acl = ACL_NOT_CACHED;
> spin_unlock(&inode->i_lock);
> if (old_access != ACL_NOT_CACHED)
> - posix_acl_release(old_access);
> + base_acl_put(old_access);
> if (old_default != ACL_NOT_CACHED)
> - posix_acl_release(old_default);
> + base_acl_put(old_default);
> }
> EXPORT_SYMBOL(forget_all_cached_acls);
>
> @@ -128,7 +129,7 @@ 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);
> @@ -161,7 +162,7 @@ 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;
> }
> @@ -383,7 +384,7 @@ 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); */
> + /* assert(base_acl_refcount(&acl->a_base) == 1); */
>
> FOREACH_ACL_ENTRY(pa, acl, pe) {
> switch(pa->e_tag) {
> @@ -438,7 +439,7 @@ 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); */
> + /* assert(base_acl_refcount(&acl->a_base) == 1); */
>
> FOREACH_ACL_ENTRY(pa, acl, pe) {
> switch(pa->e_tag) {
> diff --git a/fs/richacl_base.c b/fs/richacl_base.c
> index 69b806c..5826842 100644
> --- a/fs/richacl_base.c
> +++ b/fs/richacl_base.c
> @@ -33,7 +33,7 @@ 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;
> @@ -52,7 +52,7 @@ 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 ba91a89..2fd840e 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -576,6 +576,12 @@ static inline void mapping_allow_writable(struct address_space *mapping)
> #define i_size_ordered_init(inode) do { } while (0)
> #endif
>
> +struct base_acl {
> + union {
> + atomic_t ba_refcount;
> + struct rcu_head ba_rcu;
> + };
> +};
> struct posix_acl;
> #define ACL_NOT_CACHED ((void *)(-1))
>
> @@ -595,9 +601,9 @@ 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;
> @@ -3059,4 +3065,26 @@ static inline bool dir_relax(struct inode *inode)
>
> extern bool path_noexec(const struct path *path);
>
> +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);
> +}
> +
> +static inline int base_acl_refcount(struct base_acl *acl)
> +{
> + return atomic_read(&acl->ba_refcount);
> +}
> +
> #endif /* _LINUX_FS_H */
> diff --git a/include/linux/posix_acl.h b/include/linux/posix_acl.h
> index 5b5a80c..cef5428 100644
> --- a/include/linux/posix_acl.h
> +++ b/include/linux/posix_acl.h
> @@ -43,10 +43,7 @@ struct posix_acl_entry {
> };
>
> struct posix_acl {
> - union {
> - 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];
> };
> @@ -61,8 +58,7 @@ 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;
> }
>
> @@ -72,8 +68,8 @@ 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);
> }
>
>
> diff --git a/include/linux/richacl.h b/include/linux/richacl.h
> index 1d9f5f7..7628fad 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);
> }
>
> /**
> --
> 2.5.0
>

Cheers, Andreas

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