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NFS: teach nfs_neg_need_reval to understand LOOKUP_RCU

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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: NeilBrown <neilb@suse.de>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
This commit is contained in:
NeilBrown
2014-07-14 11:28:20 +10:00
committed by Trond Myklebust
parent f3324a2a94
commit 912a108da7
3 changed files with 52 additions and 17 deletions
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59
fs/nfs/dir.c
View File

@@ -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 @@ out_force:
*
* 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 (flags & LOOKUP_RCU)
return -ECHILD;
if (nfs_neg_need_reval(dir, dentry, flags))
if (nfs_neg_need_reval(dir, dentry, flags)) {
if (flags & LOOKUP_RCU)
return -ECHILD;
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;
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_is_exclusive_create(dir, flags) &&
nfs_check_verifier(dir, dentry, flags & LOOKUP_RCU)) {
if (flags & LOOKUP_RCU)
return -ECHILD;
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)
return -ECHILD;
parent = dget_parent(dentry);
dir = parent->d_inode;
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;
dput(parent);
else if (flags & LOOKUP_RCU)
ret = -ECHILD;
if (!(flags & LOOKUP_RCU))
dput(parent);
else if (parent != rcu_dereference(dentry))
return -ECHILD;
goto out;
}