[PATCH 4.19 05/32] NFSv4: Fix lookup revalidate of regular files

Greg Kroah-Hartman
2019-08-02T09:56:13Z

From: Trond Myklebust <trond.myklebust@hammerspace.com>

commit c7944ebb9ce9461079659e9e6ec5baaf73724b3b upstream.

If we're revalidating an existing dentry in order to open a file, we need
to ensure that we check the directory has not changed before we optimise
away the lookup.

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: Qian Lu <luqia@amazon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
fs/nfs/dir.c | 79 +++++++++++++++++++++++++++++------------------------------
1 file changed, 39 insertions(+), 40 deletions(-)

--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -1231,7 +1231,8 @@ out_bad:
}

static int
-nfs_lookup_revalidate(struct dentry *dentry, unsigned int flags)
+__nfs_lookup_revalidate(struct dentry *dentry, unsigned int flags,
+ int (*reval)(struct inode *, struct dentry *, unsigned int))
{
struct dentry *parent;
struct inode *dir;
@@ -1242,17 +1243,22 @@ nfs_lookup_revalidate(struct dentry *den
dir = d_inode_rcu(parent);
if (!dir)
return -ECHILD;
- ret = nfs_do_lookup_revalidate(dir, dentry, flags);
+ ret = reval(dir, dentry, flags);
if (parent != READ_ONCE(dentry->d_parent))
return -ECHILD;
} else {
parent = dget_parent(dentry);
- ret = nfs_do_lookup_revalidate(d_inode(parent), dentry, flags);
+ ret = reval(d_inode(parent), dentry, flags);
dput(parent);
}
return ret;
}

+static int nfs_lookup_revalidate(struct dentry *dentry, unsigned int flags)
+{
+ return __nfs_lookup_revalidate(dentry, flags, nfs_do_lookup_revalidate);
+}
+
/*
* A weaker form of d_revalidate for revalidating just the d_inode(dentry)
* when we don't really care about the dentry name. This is called when a
@@ -1609,62 +1615,55 @@ no_open:
}
EXPORT_SYMBOL_GPL(nfs_atomic_open);

-static int nfs4_lookup_revalidate(struct dentry *dentry, unsigned int flags)
+static int
+nfs4_do_lookup_revalidate(struct inode *dir, struct dentry *dentry,
+ unsigned int flags)
{
struct inode *inode;
- int ret = 0;

if (!(flags & LOOKUP_OPEN) || (flags & LOOKUP_DIRECTORY))
- goto no_open;
+ goto full_reval;
if (d_mountpoint(dentry))
- goto no_open;
- if (NFS_SB(dentry->d_sb)->caps & NFS_CAP_ATOMIC_OPEN_V1)
- goto no_open;
+ goto full_reval;

inode = d_inode(dentry);

/* We can't create new files in nfs_open_revalidate(), so we
* optimize away revalidation of negative dentries.
*/
- if (inode == NULL) {
- struct dentry *parent;
- struct inode *dir;
-
- if (flags & LOOKUP_RCU) {
- parent = READ_ONCE(dentry->d_parent);
- dir = d_inode_rcu(parent);
- if (!dir)
- return -ECHILD;
- } else {
- parent = dget_parent(dentry);
- dir = d_inode(parent);
- }
- 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 != READ_ONCE(dentry->d_parent))
- return -ECHILD;
- goto out;
- }
+ if (inode == NULL)
+ goto full_reval;
+
+ if (NFS_PROTO(dir)->have_delegation(inode, FMODE_READ))
+ return nfs_lookup_revalidate_delegated(dir, dentry, inode);

/* NFS only supports OPEN on regular files */
if (!S_ISREG(inode->i_mode))
- goto no_open;
+ goto full_reval;
+
/* We cannot do exclusive creation on a positive dentry */
- if (flags & LOOKUP_EXCL)
- goto no_open;
+ if (flags & (LOOKUP_EXCL | LOOKUP_REVAL))
+ goto reval_dentry;
+
+ /* Check if the directory changed */
+ if (!nfs_check_verifier(dir, dentry, flags & LOOKUP_RCU))
+ goto reval_dentry;

/* Let f_op->open() actually open (and revalidate) the file */
- ret = 1;
+ return 1;
+reval_dentry:
+ if (flags & LOOKUP_RCU)
+ return -ECHILD;
+ return nfs_lookup_revalidate_dentry(dir, dentry, inode);;

-out:
- return ret;
+full_reval:
+ return nfs_do_lookup_revalidate(dir, dentry, flags);
+}

-no_open:
- return nfs_lookup_revalidate(dentry, flags);
+static int nfs4_lookup_revalidate(struct dentry *dentry, unsigned int flags)
+{
+ return __nfs_lookup_revalidate(dentry, flags,
+ nfs4_do_lookup_revalidate);
}

#endif /* CONFIG_NFSV4 */