If we skip lookup revalidataion while holding a delegation, we might miss that the file has changed directories on the server. This can happen if the file is moved in between the client caching a dentry and obtaining a delegation. That can be reproduced on a single system with this bash: mkdir -p /exports/dir{1,2} exportfs -o rw localhost:/exports mount -t nfs -ov4.1,noac localhost:/exports /mnt/localhost touch /exports/dir1/fubar cat /mnt/localhost/dir1/fubar mv /mnt/localhost/dir{1,2}/fubar mv /exports/dir{2,1}/fubar cat /mnt/localhost/dir1/fubar mv /mnt/localhost/dir{1,2}/fubar In this example, the final `mv` will stat source and destination and find they are the same dentry. To fix this without giving up the increased lookup performance that holding a delegation provides, let's revalidate the dentry only once after obtaining a delegation by placing a magic value in the dentry's verifier. Suggested-by: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx> Signed-off-by: Benjamin Coddington <bcodding@xxxxxxxxxx> --- fs/nfs/dir.c | 22 ++++++++++++++++++++-- 1 file changed, 20 insertions(+), 2 deletions(-) diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c index e180033e35cf..e9d07dcd6d6f 100644 --- a/fs/nfs/dir.c +++ b/fs/nfs/dir.c @@ -949,6 +949,7 @@ static int nfs_fsync_dir(struct file *filp, loff_t start, loff_t end, return 0; } +#define NFS_DELEGATION_VERF 0xfeeddeaf /** * nfs_force_lookup_revalidate - Mark the directory as having changed * @dir: pointer to directory inode @@ -962,6 +963,8 @@ static int nfs_fsync_dir(struct file *filp, loff_t start, loff_t end, void nfs_force_lookup_revalidate(struct inode *dir) { NFS_I(dir)->cache_change_attribute++; + if (NFS_I(dir)->cache_change_attribute == NFS_DELEGATION_VERF) + NFS_I(dir)->cache_change_attribute++; } EXPORT_SYMBOL_GPL(nfs_force_lookup_revalidate); @@ -1133,6 +1136,7 @@ nfs_lookup_revalidate_dentry(struct inode *dir, struct dentry *dentry, struct nfs_fh *fhandle; struct nfs_fattr *fattr; struct nfs4_label *label; + unsigned long verifier; int ret; ret = -ENOMEM; @@ -1154,6 +1158,11 @@ nfs_lookup_revalidate_dentry(struct inode *dir, struct dentry *dentry, if (nfs_refresh_inode(inode, fattr) < 0) goto out; + if (NFS_PROTO(dir)->have_delegation(inode, FMODE_READ)) + verifier = NFS_DELEGATION_VERF; + else + verifier = nfs_save_change_attribute(dir); + nfs_setsecurity(inode, fattr, label); nfs_set_verifier(dentry, nfs_save_change_attribute(dir)); @@ -1167,6 +1176,15 @@ nfs_lookup_revalidate_dentry(struct inode *dir, struct dentry *dentry, return nfs_lookup_revalidate_done(dir, dentry, inode, ret); } +static int nfs_delegation_matches_dentry(struct inode *dir, + struct dentry *dentry, struct inode *inode) +{ + if (NFS_PROTO(dir)->have_delegation(inode, FMODE_READ) && + dentry->d_time == NFS_DELEGATION_VERF) + return 1; + return 0; +} + /* * This is called every time the dcache has a lookup hit, * and we should check whether we can really trust that @@ -1197,7 +1215,7 @@ nfs_do_lookup_revalidate(struct inode *dir, struct dentry *dentry, goto out_bad; } - if (NFS_PROTO(dir)->have_delegation(inode, FMODE_READ)) + if (nfs_delegation_matches_dentry(dir, dentry, inode)) return nfs_lookup_revalidate_delegated(dir, dentry, inode); /* Force a full look up iff the parent directory has changed */ @@ -1635,7 +1653,7 @@ nfs4_do_lookup_revalidate(struct inode *dir, struct dentry *dentry, if (inode == NULL) goto full_reval; - if (NFS_PROTO(dir)->have_delegation(inode, FMODE_READ)) + if (nfs_delegation_matches_dentry(dir, dentry, inode)) return nfs_lookup_revalidate_delegated(dir, dentry, inode); /* NFS only supports OPEN on regular files */ -- 2.20.1