fs: provide simple rcu-walk generic_check_acl implementation (1e1743eb) · Commits · 戴 / test

This simple implementation just checks for no ACLs on the inode, and if so, then the rcu-walk may proceed, otherwise fail it. This could easily be extended to put acls under RCU and check them under seqlock, if need be. But this implementation is enough to show the rcu-walk aware permissions code for path lookups is working, and will handle cases where there are no ACLs or ACLs in just the final element. This patch implicity converts tmpfs to rcu-aware permission check. Subsequent patches onvert ext*, xfs, and, btrfs. Each of these uses acl/permission code in a different way, so convert them all to provide templates and proof of concept. Signed-off-by:

Nick Piggin <npiggin@kernel.dk>

fs/generic_acl.c

+12 −10

Original line number	Diff line number	Diff line
		@@ -192,10 +192,11 @@ generic_acl_chmod(struct inode *inode)
		int
		generic_check_acl(struct inode *inode, int mask, unsigned int flags)
		{
		struct posix_acl *acl;

		if (flags & IPERM_FLAG_RCU)
		if (flags & IPERM_FLAG_RCU) {
		if (!negative_cached_acl(inode, ACL_TYPE_ACCESS))
		return -ECHILD;
		} else {
		struct posix_acl *acl;

		acl = get_cached_acl(inode, ACL_TYPE_ACCESS);
		if (acl) {
		@@ -203,6 +204,7 @@ generic_check_acl(struct inode *inode, int mask, unsigned int flags)
		posix_acl_release(acl);
		return error;
		}
		}
		return -EAGAIN;
		}

include/linux/posix_acl.h

+19 −0

Original line number	Diff line number	Diff line
		@@ -108,6 +108,25 @@ 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)
		{
		struct posix_acl *p, acl;
		switch (type) {
		case ACL_TYPE_ACCESS:
		p = &inode->i_acl;
		break;
		case ACL_TYPE_DEFAULT:
		p = &inode->i_default_acl;
		break;
		default:
		BUG();
		}
		acl = ACCESS_ONCE(*p);
		if (acl)
		return 0;
		return 1;
		}

		static inline void set_cached_acl(struct inode *inode,
		int type,
		struct posix_acl *acl)

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