Re: [PATCH -V1 19/22] vfs: Cache richacl in struct inode

Dave Chinner
2014-04-29T00:52:13Z

On Sun, Apr 27, 2014 at 09:44:50PM +0530, Aneesh Kumar K.V wrote:
> From: Andreas Gruenbacher <agruen@kernel.org>
>
> Cache richacls in struct inode so that this doesn't have to be done
> individually in each filesystem.
>
> Signed-off-by: Andreas Gruenbacher <agruen@kernel.org>
> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
> ---
> fs/inode.c | 25 ++++++++++++++++++-----
> include/linux/fs.h | 12 +++++++++--
> include/linux/richacl.h | 53 +++++++++++++++++++++++++++++++++++++++++++++++++
> 3 files changed, 83 insertions(+), 7 deletions(-)
>
> diff --git a/fs/inode.c b/fs/inode.c
> index f96d2a6f88cc..b96a16d5c653 100644
> --- a/fs/inode.c
> +++ b/fs/inode.c
> @@ -18,6 +18,7 @@
> #include <linux/buffer_head.h> /* for inode_has_buffers */
> #include <linux/ratelimit.h>
> #include <linux/list_lru.h>
> +#include <linux/richacl.h>
> #include "internal.h"
>
> /*
> @@ -185,7 +186,12 @@ int inode_init_always(struct super_block *sb, struct inode *inode)
> inode->i_mapping = mapping;
> INIT_HLIST_HEAD(&inode->i_dentry); /* buggered by rcu freeing */
> #ifdef CONFIG_FS_POSIX_ACL
> - inode->i_acl = inode->i_default_acl = ACL_NOT_CACHED;
> + if (IS_POSIXACL(inode))
> + inode->i_acl = inode->i_default_acl = ACL_NOT_CACHED;
> +#endif
> +#ifdef CONFIG_FS_RICHACL
> + if (IS_RICHACL(inode))
> + inode->i_richacl = ACL_NOT_CACHED;
> #endif

That's just plain wrong. i think this is what Christoph didn't like.
An inode can have either a POSIX ACL or a RICH ACL, so there is no
need for multiple pointers in the inode for them.

>
> #ifdef CONFIG_FSNOTIFY
> @@ -240,10 +246,19 @@ 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);
> - if (inode->i_default_acl && inode->i_default_acl != ACL_NOT_CACHED)
> - posix_acl_release(inode->i_default_acl);
> + if (IS_POSIXACL(inode)) {
> + if (inode->i_acl && inode->i_acl != ACL_NOT_CACHED)
> + posix_acl_release(inode->i_acl);
> + if (inode->i_default_acl &&
> + inode->i_default_acl != ACL_NOT_CACHED)
> + posix_acl_release(inode->i_default_acl);
> + }
> +#endif
> +#ifdef CONFIG_FS_RICHACL
> + if (IS_RICHACL(inode)) {
> + if (inode->i_richacl && inode->i_richacl != ACL_NOT_CACHED)
> + richacl_put(inode->i_richacl);
> + }
> #endif

if (inode->i_acl && inode->i_acl != ACL_NOT_CACHED)
acl_release(inode->i_acl);

And all the mess of working out what acl needs releasing get taken
out of of this code.

> index 22d85798b520..95df64d21e55 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -492,6 +492,7 @@ static inline int mapping_writably_mapped(struct address_space *mapping)
> #endif
>
> struct posix_acl;
> +struct richacl;
> #define ACL_NOT_CACHED ((void *)(-1))
>
> #define IOP_FASTPERM 0x0001
> @@ -510,10 +511,17 @@ struct inode {
> kgid_t i_gid;
> unsigned int i_flags;
>
> + union {
> #ifdef CONFIG_FS_POSIX_ACL
> - struct posix_acl *i_acl;
> - struct posix_acl *i_default_acl;
> + struct {
> + struct posix_acl *i_acl;
> + struct posix_acl *i_default_acl;
> + };
> #endif
> +#ifdef CONFIG_FS_RICHACL
> + struct richacl *i_richacl;
> +#endif
> + };

>
> const struct inode_operations *i_op;
> struct super_block *i_sb;
> diff --git a/include/linux/richacl.h b/include/linux/richacl.h
> index 88f95d78b897..a7db341e4ee9 100644
> --- a/include/linux/richacl.h
> +++ b/include/linux/richacl.h
> @@ -191,6 +191,59 @@ richacl_put(struct richacl *acl)
> kfree(acl);
> }
>
> +#ifdef CONFIG_FS_RICHACL
> +static inline struct richacl *get_cached_richacl(struct inode *inode)
> +{
> + struct richacl **p, *acl;
> +
> + p = &inode->i_richacl;
> + acl = ACCESS_ONCE(*p);
> + if (acl) {
> + spin_lock(&inode->i_lock);
> + acl = *p;
> + if (acl != ACL_NOT_CACHED)
> + acl = richacl_get(acl);
> + spin_unlock(&inode->i_lock);
> + }
> + return acl;
> +}
> +
> +static inline void set_cached_richacl(struct inode *inode,
> + struct richacl *acl)
> +{
> + struct richacl *old = NULL;
> + spin_lock(&inode->i_lock);
> + old = inode->i_richacl;
> + inode->i_richacl = richacl_get(acl);
> + spin_unlock(&inode->i_lock);
> + if (old != ACL_NOT_CACHED)
> + richacl_put(old);
> +}
> +
> +static inline void forget_cached_richacl(struct inode *inode)
> +{
> + struct richacl *old = NULL;
> + spin_lock(&inode->i_lock);
> + old = inode->i_richacl;
> + inode->i_richacl = ACL_NOT_CACHED;
> + spin_unlock(&inode->i_lock);
> + if (old != ACL_NOT_CACHED)
> + richacl_put(old);
> +}
> +
> +static inline int negative_cached_richacl(struct inode *inode)
> +{
> + struct richacl **p, *acl;
> +
> + p = &inode->i_richacl;
> + acl = ACCESS_ONCE(*p);
> + if (acl)
> + return 0;
> + return 1;
> +}
> +
> +#endif

This is all just copy-and-paste from the posix_acl code with the RCU
path-walk awareness removed from it. There should only be a single
RCU aware version of these functions that does not care what type of
ACL is in use.

Cheers,

Dave.
--
Dave Chinner
david@fromorbit.com