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Commit 3567866b authored by Al Viro's avatar Al Viro
Browse files

RCUify freeing acls, let check_acl() go ahead in RCU mode if acl is cached 



Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent 951c0d66

fs/namei.c

+6 −11
Original line number Diff line number Diff line
@@ -179,19 +179,14 @@ static int check_acl(struct inode *inode, int mask) 
#ifdef CONFIG_FS_POSIX_ACL

	struct posix_acl *acl;



	/*

	 * Under RCU walk, we cannot even do a "get_cached_acl()",

	 * because that involves locking and getting a refcount on

	 * a cached ACL.

	 *

	 * So the only case we handle during RCU walking is the

	 * case of a cached "no ACL at all", which needs no locks

	 * or refcounts.

	 */

	if (mask & MAY_NOT_BLOCK) {

	        if (negative_cached_acl(inode, ACL_TYPE_ACCESS))

		acl = get_cached_acl_rcu(inode, ACL_TYPE_ACCESS);

	        if (!acl)

	                return -EAGAIN;

		/* no ->get_acl() calls in RCU mode... */

		if (acl == ACL_NOT_CACHED)

			return -ECHILD;

	        return posix_acl_permission(inode, acl, mask);

	}



	acl = get_cached_acl(inode, ACL_TYPE_ACCESS);

include/linux/posix_acl.h

+9 −9
Original line number Diff line number Diff line
@@ -9,6 +9,7 @@ 
#define __LINUX_POSIX_ACL_H



#include <linux/slab.h>

#include <linux/rcupdate.h>



#define ACL_UNDEFINED_ID	(-1)
@@ -38,7 +39,10 @@ struct posix_acl_entry { 
};



struct posix_acl {

	union {

		atomic_t		a_refcount;

		struct rcu_head		a_rcu;

	};

	unsigned int		a_count;

	struct posix_acl_entry	a_entries[0];

};
@@ -65,7 +69,7 @@ static inline void 
posix_acl_release(struct posix_acl *acl)

{

	if (acl && atomic_dec_and_test(&acl->a_refcount))

		kfree(acl);

		kfree_rcu(acl, a_rcu);

}
@@ -110,13 +114,9 @@ static inline struct posix_acl *get_cached_acl(struct inode *inode, int type) 
	return acl;

}



static inline int negative_cached_acl(struct inode *inode, int type)

static inline struct posix_acl *get_cached_acl_rcu(struct inode *inode, int type)

{

	struct posix_acl **p = acl_by_type(inode, type);

	struct posix_acl *acl = ACCESS_ONCE(*p);

	if (acl)

		return 0;

	return 1;

	return rcu_dereference(*acl_by_type(inode, type));

}



static inline void set_cached_acl(struct inode *inode,
@@ -127,7 +127,7 @@ static inline void set_cached_acl(struct inode *inode, 
	struct posix_acl *old;

	spin_lock(&inode->i_lock);

	old = *p;

	*p = posix_dup_acl(acl);

	rcu_assign_pointer(*p, posix_acl_dup(acl));

	spin_unlock(&inode->i_lock);

	if (old != ACL_NOT_CACHED)

		posix_acl_release(old);