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@xxxxxxx>
---
fs/nfs/dir.c | 59 ++++++++++++++++++++++++++++++++++--------------
fs/nfs/inode.c | 9 +++++++
include/linux/nfs_fs.h | 1 +
3 files changed, 52 insertions(+), 17 deletions(-)
diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
index ac958f29e558..de9bc809c7ea 100644
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -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;
}
diff --git a/fs/nfs/inode.c b/fs/nfs/inode.c
index abd37a380535..432b6c4bea47 100644
--- a/fs/nfs/inode.c
+++ b/fs/nfs/inode.c
@@ -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);
diff --git a/include/linux/nfs_fs.h b/include/linux/nfs_fs.h
index e30f6059ecd6..60cd9e377926 100644
--- a/include/linux/nfs_fs.h
+++ b/include/linux/nfs_fs.h
@@ -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 *);
--
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