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Commit 912a108d authored by NeilBrown's avatar NeilBrown Committed by Trond Myklebust
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NFS: teach nfs_neg_need_reval to understand LOOKUP_RCU 



This requires nfs_check_verifier to take an rcu_walk flag, and requires
an rcu version of nfs_revalidate_inode which returns -ECHILD rather
than making an RPC call.

With this, nfs_lookup_revalidate can call nfs_neg_need_reval in
RCU-walk mode.

We can also move the LOOKUP_RCU check past the nfs_check_verifier()
call in nfs_lookup_revalidate.

If RCU_WALK prevents nfs_check_verifier or nfs_neg_need_reval from
doing a full check, they return a status indicating that a revalidation
is required.  As this revalidation will not be possible in RCU_WALK
mode, -ECHILD will ultimately be returned, which is the desired result.

Signed-off-by: default avatarNeilBrown <neilb@suse.de>
Signed-off-by: default avatarTrond Myklebust <trond.myklebust@primarydata.com>
parent f3324a2a

fs/nfs/dir.c

+42 −17
Original line number Diff line number Diff line
@@ -988,9 +988,13 @@ EXPORT_SYMBOL_GPL(nfs_force_lookup_revalidate); 
 * A check for whether or not the parent directory has changed.

 * In the case it has, we assume that the dentries are untrustworthy

 * and may need to be looked up again.

 * If rcu_walk prevents us from performing a full check, return 0.

 */

static int nfs_check_verifier(struct inode *dir, struct dentry *dentry)

static int nfs_check_verifier(struct inode *dir, struct dentry *dentry,

			      int rcu_walk)

{

	int ret;



	if (IS_ROOT(dentry))

		return 1;

	if (NFS_SERVER(dir)->flags & NFS_MOUNT_LOOKUP_CACHE_NONE)
@@ -998,7 +1002,11 @@ static int nfs_check_verifier(struct inode *dir, struct dentry *dentry) 
	if (!nfs_verify_change_attribute(dir, dentry->d_time))

		return 0;

	/* Revalidate nfsi->cache_change_attribute before we declare a match */

	if (nfs_revalidate_inode(NFS_SERVER(dir), dir) < 0)

	if (rcu_walk)

		ret = nfs_revalidate_inode_rcu(NFS_SERVER(dir), dir);

	else

		ret = nfs_revalidate_inode(NFS_SERVER(dir), dir);

	if (ret < 0)

		return 0;

	if (!nfs_verify_change_attribute(dir, dentry->d_time))

		return 0;
@@ -1054,6 +1062,9 @@ int nfs_lookup_verify_inode(struct inode *inode, unsigned int flags) 
 *

 * If parent mtime has changed, we revalidate, else we wait for a

 * period corresponding to the parent's attribute cache timeout value.

 *

 * If LOOKUP_RCU prevents us from performing a full check, return 1

 * suggesting a reval is needed.

 */

static inline

int nfs_neg_need_reval(struct inode *dir, struct dentry *dentry,
@@ -1064,7 +1075,7 @@ int nfs_neg_need_reval(struct inode *dir, struct dentry *dentry, 
		return 0;

	if (NFS_SERVER(dir)->flags & NFS_MOUNT_LOOKUP_CACHE_NONEG)

		return 1;

	return !nfs_check_verifier(dir, dentry);

	return !nfs_check_verifier(dir, dentry, flags & LOOKUP_RCU);

}



/*
@@ -1101,11 +1112,11 @@ static int nfs_lookup_revalidate(struct dentry *dentry, unsigned int flags) 
	inode = dentry->d_inode;



	if (!inode) {

		if (nfs_neg_need_reval(dir, dentry, flags)) {

			if (flags & LOOKUP_RCU)

				return -ECHILD;



		if (nfs_neg_need_reval(dir, dentry, flags))

			goto out_bad;

		}

		goto out_valid_noent;

	}
@@ -1120,16 +1131,21 @@ static int nfs_lookup_revalidate(struct dentry *dentry, unsigned int flags) 
	if (NFS_PROTO(dir)->have_delegation(inode, FMODE_READ))

		goto out_set_verifier;



	/* Force a full look up iff the parent directory has changed */

	if (!nfs_is_exclusive_create(dir, flags) &&

	    nfs_check_verifier(dir, dentry, flags & LOOKUP_RCU)) {



		if (flags & LOOKUP_RCU)

			return -ECHILD;



	/* Force a full look up iff the parent directory has changed */

	if (!nfs_is_exclusive_create(dir, flags) && nfs_check_verifier(dir, dentry)) {

		if (nfs_lookup_verify_inode(inode, flags))

			goto out_zap_parent;

		goto out_valid;

	}



	if (flags & LOOKUP_RCU)

		return -ECHILD;



	if (NFS_STALE(inode))

		goto out_bad;
@@ -1566,14 +1582,23 @@ static int nfs4_lookup_revalidate(struct dentry *dentry, unsigned int flags) 
		struct dentry *parent;

		struct inode *dir;



		if (flags & LOOKUP_RCU)

		if (flags & LOOKUP_RCU) {

			parent = rcu_dereference(dentry);

			dir = ACCESS_ONCE(parent->d_inode);

			if (!dir)

				return -ECHILD;



		} else {

			parent = dget_parent(dentry);

			dir = parent->d_inode;

		}

		if (!nfs_neg_need_reval(dir, dentry, flags))

			ret = 1;

		else if (flags & LOOKUP_RCU)

			ret = -ECHILD;

		if (!(flags & LOOKUP_RCU))

			dput(parent);

		else if (parent != rcu_dereference(dentry))

			return -ECHILD;

		goto out;

	}

fs/nfs/inode.c

+9 −0
Original line number Diff line number Diff line
@@ -1002,6 +1002,15 @@ int nfs_revalidate_inode(struct nfs_server *server, struct inode *inode) 
}

EXPORT_SYMBOL_GPL(nfs_revalidate_inode);



int nfs_revalidate_inode_rcu(struct nfs_server *server, struct inode *inode)

{

	if (!(NFS_I(inode)->cache_validity &

			(NFS_INO_INVALID_ATTR|NFS_INO_INVALID_LABEL))

			&& !nfs_attribute_cache_expired(inode))

		return NFS_STALE(inode) ? -ESTALE : 0;

	return -ECHILD;

}



static int nfs_invalidate_mapping(struct inode *inode, struct address_space *mapping)

{

	struct nfs_inode *nfsi = NFS_I(inode);

include/linux/nfs_fs.h

+1 −0
Original line number Diff line number Diff line
@@ -352,6 +352,7 @@ extern int nfs_release(struct inode *, struct file *); 
extern int nfs_attribute_timeout(struct inode *inode);

extern int nfs_attribute_cache_expired(struct inode *inode);

extern int nfs_revalidate_inode(struct nfs_server *server, struct inode *inode);

extern int nfs_revalidate_inode_rcu(struct nfs_server *server, struct inode *inode);

extern int __nfs_revalidate_inode(struct nfs_server *, struct inode *);

extern int nfs_revalidate_mapping(struct inode *inode, struct address_space *mapping);

extern int nfs_setattr(struct dentry *, struct iattr *);