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

["Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>]

Dave Chinner <david@fromorbit.com> writes:

> 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.

We don't really have multiple pointers

	union {
#ifdef CONFIG_FS_POSIX_ACL
		struct {
			struct posix_acl *i_acl;
			struct posix_acl *i_default_acl;
		};
#endif
#ifdef CONFIG_FS_RICHACL
		struct richacl	*i_richacl;
#endif
	};


But I understand what you are suggesting here. Will try to rework and
see how much easy/simpler it makes the code. 

>
>>  
>>  #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.

Understood. Will try to see how much I can simplify.

>
>> 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.
>

Ok.

-aneesh