I'd like to bump this one again while we're talking about
lookup/revalidation.
We have folks that hit this problem in the field:
- client caches a dentry
- file gets moved
- server gives out a delegation
- client never notices the change because we always skip
revalidation
Is this the wrong place to fix this? Any other feedback?
Ben
On 19 Sep 2019, at 10:49, Benjamin Coddington wrote:
If we skip lookup revalidation while holding a delegation, we might
miss
that the file has changed directories on the server. The directory's
change attribute should still be checked against the dentry's d_time
to
perform a complete revalidation.
V2 - Add some commentary as suggested-by J. Bruce Fields.
Signed-off-by: Benjamin Coddington <bcodding@xxxxxxxxxx>
---
fs/nfs/dir.c | 17 +++++++++++------
1 file changed, 11 insertions(+), 6 deletions(-)
diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
index 0adfd8840110..8723e82f5c9d 100644
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -1197,12 +1197,20 @@ nfs_do_lookup_revalidate(struct inode *dir,
struct dentry *dentry,
goto out_bad;
}
- if (NFS_PROTO(dir)->have_delegation(inode, FMODE_READ))
- return nfs_lookup_revalidate_delegated(dir, dentry, inode);
-
/* Force a full look up iff the parent directory has changed */
if (!(flags & (LOOKUP_EXCL | LOOKUP_REVAL)) &&
nfs_check_verifier(dir, dentry, flags & LOOKUP_RCU)) {
+
+ /*
+ * Note that the file can't move while we hold a
+ * delegation. But this dentry could have been cached
+ * before we got a delegation. So it's only safe to
+ * skip revalidation when the parent directory is
+ * unchanged:
+ */
+ if (NFS_PROTO(dir)->have_delegation(inode, FMODE_READ))
+ return nfs_lookup_revalidate_delegated(dir, dentry, inode);
+
error = nfs_lookup_verify_inode(inode, flags);
if (error) {
if (error == -ESTALE)
@@ -1635,9 +1643,6 @@ 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))
- return nfs_lookup_revalidate_delegated(dir, dentry, inode);
-
/* NFS only supports OPEN on regular files */
if (!S_ISREG(inode->i_mode))
goto full_reval;
--
2.20.1
