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

[Dave Chinner <david-FqsqvQoI3Ljby3iVrkZq2A@public.gmane.org>]

On Sun, Apr 27, 2014 at 09:44:50PM +0530, Aneesh Kumar K.V wrote:
> From: Andreas Gruenbacher <agruen-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.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-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>
> ---
>  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-FqsqvQoI3Ljby3iVrkZq2A@public.gmane.org
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