vfs: kill FS_REVAL_DOT by adding a d_weak_revalidate dentry op
The following set of operations on a NFS client and server will cause
server# mkdir a
client# cd a
server# mv a a.bak
client# sleep 30 # (or whatever the dir attrcache timeout is)
client# stat .
stat: cannot stat `.': Stale NFS file handle
Obviously, we should not be getting an ESTALE error back there since the
inode still exists on the server. The problem is that the lookup code
will call d_revalidate on the dentry that "." refers to, because NFS has
FS_REVAL_DOT set.
nfs_lookup_revalidate will see that the parent directory has changed and
will try to reverify the dentry by redoing a LOOKUP. That of course
fails, so the lookup code returns ESTALE.
The problem here is that d_revalidate is really a bad fit for this case.
What we really want to know at this point is whether the inode is still
good or not, but we don't really care what name it goes by or whether
the dcache is still valid.
Add a new d_op->d_weak_revalidate operation and have complete_walk call
that instead of d_revalidate. The intent there is to allow for a
"weaker" d_revalidate that just checks to see whether the inode is still
good. This is also gives us an opportunity to kill off the FS_REVAL_DOT
special casing.
[AV: changed method name, added note in porting, fixed confusion re
having it possibly called from RCU mode (it won't be)]
Cc: NeilBrown <neilb@suse.de>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/Documentation/filesystems/Locking b/Documentation/filesystems/Locking
index f48e0c6..0706d32 100644
--- a/Documentation/filesystems/Locking
+++ b/Documentation/filesystems/Locking
@@ -10,6 +10,7 @@
--------------------------- dentry_operations --------------------------
prototypes:
int (*d_revalidate)(struct dentry *, unsigned int);
+ int (*d_weak_revalidate)(struct dentry *, unsigned int);
int (*d_hash)(const struct dentry *, const struct inode *,
struct qstr *);
int (*d_compare)(const struct dentry *, const struct inode *,
@@ -25,6 +26,7 @@
locking rules:
rename_lock ->d_lock may block rcu-walk
d_revalidate: no no yes (ref-walk) maybe
+d_weak_revalidate:no no yes no
d_hash no no no maybe
d_compare: yes no no maybe
d_delete: no yes no no
diff --git a/Documentation/filesystems/porting b/Documentation/filesystems/porting
index 0472c31..4db22f6 100644
--- a/Documentation/filesystems/porting
+++ b/Documentation/filesystems/porting
@@ -441,3 +441,7 @@
two, it gets "is it an O_EXCL or equivalent?" boolean argument. Note that
local filesystems can ignore tha argument - they are guaranteed that the
object doesn't exist. It's remote/distributed ones that might care...
+--
+[mandatory]
+ FS_REVAL_DOT is gone; if you used to have it, add ->d_weak_revalidate()
+in your dentry operations instead.
diff --git a/Documentation/filesystems/vfs.txt b/Documentation/filesystems/vfs.txt
index e3869098..bc4b06b 100644
--- a/Documentation/filesystems/vfs.txt
+++ b/Documentation/filesystems/vfs.txt
@@ -900,6 +900,7 @@
struct dentry_operations {
int (*d_revalidate)(struct dentry *, unsigned int);
+ int (*d_weak_revalidate)(struct dentry *, unsigned int);
int (*d_hash)(const struct dentry *, const struct inode *,
struct qstr *);
int (*d_compare)(const struct dentry *, const struct inode *,
@@ -915,8 +916,13 @@
d_revalidate: called when the VFS needs to revalidate a dentry. This
is called whenever a name look-up finds a dentry in the
- dcache. Most filesystems leave this as NULL, because all their
- dentries in the dcache are valid
+ dcache. Most local filesystems leave this as NULL, because all their
+ dentries in the dcache are valid. Network filesystems are different
+ since things can change on the server without the client necessarily
+ being aware of it.
+
+ This function should return a positive value if the dentry is still
+ valid, and zero or a negative error code if it isn't.
d_revalidate may be called in rcu-walk mode (flags & LOOKUP_RCU).
If in rcu-walk mode, the filesystem must revalidate the dentry without
@@ -927,6 +933,20 @@
If a situation is encountered that rcu-walk cannot handle, return
-ECHILD and it will be called again in ref-walk mode.
+ d_weak_revalidate: called when the VFS needs to revalidate a "jumped" dentry.
+ This is called when a path-walk ends at dentry that was not acquired by
+ doing a lookup in the parent directory. This includes "/", "." and "..",
+ as well as procfs-style symlinks and mountpoint traversal.
+
+ In this case, we are less concerned with whether the dentry is still
+ fully correct, but rather that the inode is still valid. As with
+ d_revalidate, most local filesystems will set this to NULL since their
+ dcache entries are always valid.
+
+ This function has the same return code semantics as d_revalidate.
+
+ d_weak_revalidate is only called after leaving rcu-walk mode.
+
d_hash: called when the VFS adds a dentry to the hash table. The first
dentry passed to d_hash is the parent directory that the name is
to be hashed into. The inode is the dentry's inode.
diff --git a/fs/9p/vfs_dentry.c b/fs/9p/vfs_dentry.c
index 64600b5..9ad6862 100644
--- a/fs/9p/vfs_dentry.c
+++ b/fs/9p/vfs_dentry.c
@@ -137,6 +137,7 @@
const struct dentry_operations v9fs_cached_dentry_operations = {
.d_revalidate = v9fs_lookup_revalidate,
+ .d_weak_revalidate = v9fs_lookup_revalidate,
.d_delete = v9fs_cached_dentry_delete,
.d_release = v9fs_dentry_release,
};
diff --git a/fs/9p/vfs_super.c b/fs/9p/vfs_super.c
index 137d503..91dad63 100644
--- a/fs/9p/vfs_super.c
+++ b/fs/9p/vfs_super.c
@@ -363,5 +363,5 @@
.mount = v9fs_mount,
.kill_sb = v9fs_kill_super,
.owner = THIS_MODULE,
- .fs_flags = FS_RENAME_DOES_D_MOVE|FS_REVAL_DOT,
+ .fs_flags = FS_RENAME_DOES_D_MOVE,
};
diff --git a/fs/dcache.c b/fs/dcache.c
index ebab049..68220dd 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -1358,6 +1358,7 @@
WARN_ON_ONCE(dentry->d_flags & (DCACHE_OP_HASH |
DCACHE_OP_COMPARE |
DCACHE_OP_REVALIDATE |
+ DCACHE_OP_WEAK_REVALIDATE |
DCACHE_OP_DELETE ));
dentry->d_op = op;
if (!op)
@@ -1368,6 +1369,8 @@
dentry->d_flags |= DCACHE_OP_COMPARE;
if (op->d_revalidate)
dentry->d_flags |= DCACHE_OP_REVALIDATE;
+ if (op->d_weak_revalidate)
+ dentry->d_flags |= DCACHE_OP_WEAK_REVALIDATE;
if (op->d_delete)
dentry->d_flags |= DCACHE_OP_DELETE;
if (op->d_prune)
diff --git a/fs/namei.c b/fs/namei.c
index 052c095..dc984fe 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -600,14 +600,10 @@
if (likely(!(nd->flags & LOOKUP_JUMPED)))
return 0;
- if (likely(!(dentry->d_flags & DCACHE_OP_REVALIDATE)))
+ if (likely(!(dentry->d_flags & DCACHE_OP_WEAK_REVALIDATE)))
return 0;
- if (likely(!(dentry->d_sb->s_type->fs_flags & FS_REVAL_DOT)))
- return 0;
-
- /* Note: we do not d_invalidate() */
- status = d_revalidate(dentry, nd->flags);
+ status = dentry->d_op->d_weak_revalidate(dentry, nd->flags);
if (status > 0)
return 0;
diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
index a8bd28c..f23f455 100644
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -1136,6 +1136,45 @@
}
/*
+ * A weaker form of d_revalidate for revalidating just the dentry->d_inode
+ * when we don't really care about the dentry name. This is called when a
+ * pathwalk ends on a dentry that was not found via a normal lookup in the
+ * parent dir (e.g.: ".", "..", procfs symlinks or mountpoint traversals).
+ *
+ * In this situation, we just want to verify that the inode itself is OK
+ * since the dentry might have changed on the server.
+ */
+static int nfs_weak_revalidate(struct dentry *dentry, unsigned int flags)
+{
+ int error;
+ struct inode *inode = dentry->d_inode;
+
+ /*
+ * I believe we can only get a negative dentry here in the case of a
+ * procfs-style symlink. Just assume it's correct for now, but we may
+ * eventually need to do something more here.
+ */
+ if (!inode) {
+ dfprintk(LOOKUPCACHE, "%s: %s/%s has negative inode\n",
+ __func__, dentry->d_parent->d_name.name,
+ dentry->d_name.name);
+ return 1;
+ }
+
+ if (is_bad_inode(inode)) {
+ dfprintk(LOOKUPCACHE, "%s: %s/%s has dud inode\n",
+ __func__, dentry->d_parent->d_name.name,
+ dentry->d_name.name);
+ return 0;
+ }
+
+ error = nfs_revalidate_inode(NFS_SERVER(inode), inode);
+ dfprintk(LOOKUPCACHE, "NFS: %s: inode %lu is %s\n",
+ __func__, inode->i_ino, error ? "invalid" : "valid");
+ return !error;
+}
+
+/*
* This is called from dput() when d_count is going to 0.
*/
static int nfs_dentry_delete(const struct dentry *dentry)
@@ -1202,6 +1241,7 @@
const struct dentry_operations nfs_dentry_operations = {
.d_revalidate = nfs_lookup_revalidate,
+ .d_weak_revalidate = nfs_weak_revalidate,
.d_delete = nfs_dentry_delete,
.d_iput = nfs_dentry_iput,
.d_automount = nfs_d_automount,
diff --git a/fs/nfs/nfs4super.c b/fs/nfs/nfs4super.c
index 84d2e9e..569b166 100644
--- a/fs/nfs/nfs4super.c
+++ b/fs/nfs/nfs4super.c
@@ -28,7 +28,7 @@
.name = "nfs4",
.mount = nfs4_remote_mount,
.kill_sb = nfs_kill_super,
- .fs_flags = FS_RENAME_DOES_D_MOVE|FS_REVAL_DOT|FS_BINARY_MOUNTDATA,
+ .fs_flags = FS_RENAME_DOES_D_MOVE|FS_BINARY_MOUNTDATA,
};
static struct file_system_type nfs4_remote_referral_fs_type = {
@@ -36,7 +36,7 @@
.name = "nfs4",
.mount = nfs4_remote_referral_mount,
.kill_sb = nfs_kill_super,
- .fs_flags = FS_RENAME_DOES_D_MOVE|FS_REVAL_DOT|FS_BINARY_MOUNTDATA,
+ .fs_flags = FS_RENAME_DOES_D_MOVE|FS_BINARY_MOUNTDATA,
};
struct file_system_type nfs4_referral_fs_type = {
@@ -44,7 +44,7 @@
.name = "nfs4",
.mount = nfs4_referral_mount,
.kill_sb = nfs_kill_super,
- .fs_flags = FS_RENAME_DOES_D_MOVE|FS_REVAL_DOT|FS_BINARY_MOUNTDATA,
+ .fs_flags = FS_RENAME_DOES_D_MOVE|FS_BINARY_MOUNTDATA,
};
static const struct super_operations nfs4_sops = {
diff --git a/fs/nfs/super.c b/fs/nfs/super.c
index 2e7e8c8..92acc26 100644
--- a/fs/nfs/super.c
+++ b/fs/nfs/super.c
@@ -292,7 +292,7 @@
.name = "nfs",
.mount = nfs_fs_mount,
.kill_sb = nfs_kill_super,
- .fs_flags = FS_RENAME_DOES_D_MOVE|FS_REVAL_DOT|FS_BINARY_MOUNTDATA,
+ .fs_flags = FS_RENAME_DOES_D_MOVE|FS_BINARY_MOUNTDATA,
};
EXPORT_SYMBOL_GPL(nfs_fs_type);
@@ -301,7 +301,7 @@
.name = "nfs",
.mount = nfs_xdev_mount,
.kill_sb = nfs_kill_super,
- .fs_flags = FS_RENAME_DOES_D_MOVE|FS_REVAL_DOT|FS_BINARY_MOUNTDATA,
+ .fs_flags = FS_RENAME_DOES_D_MOVE|FS_BINARY_MOUNTDATA,
};
const struct super_operations nfs_sops = {
@@ -331,7 +331,7 @@
.name = "nfs4",
.mount = nfs_fs_mount,
.kill_sb = nfs_kill_super,
- .fs_flags = FS_RENAME_DOES_D_MOVE|FS_REVAL_DOT|FS_BINARY_MOUNTDATA,
+ .fs_flags = FS_RENAME_DOES_D_MOVE|FS_BINARY_MOUNTDATA,
};
EXPORT_SYMBOL_GPL(nfs4_fs_type);
diff --git a/include/linux/dcache.h b/include/linux/dcache.h
index 03d1692..1a6bb81f 100644
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@@ -145,6 +145,7 @@
struct dentry_operations {
int (*d_revalidate)(struct dentry *, unsigned int);
+ int (*d_weak_revalidate)(struct dentry *, unsigned int);
int (*d_hash)(const struct dentry *, const struct inode *,
struct qstr *);
int (*d_compare)(const struct dentry *, const struct inode *,
@@ -192,6 +193,8 @@
#define DCACHE_GENOCIDE 0x0200
#define DCACHE_SHRINK_LIST 0x0400
+#define DCACHE_OP_WEAK_REVALIDATE 0x0800
+
#define DCACHE_NFSFS_RENAMED 0x1000
/* this dentry has been "silly renamed" and has to be deleted on the last
* dput() */
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 7f47152..da94011 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1807,7 +1807,6 @@
#define FS_HAS_SUBTYPE 4
#define FS_USERNS_MOUNT 8 /* Can be mounted by userns root */
#define FS_USERNS_DEV_MOUNT 16 /* A userns mount does not imply MNT_NODEV */
-#define FS_REVAL_DOT 16384 /* Check the paths ".", ".." for staleness */
#define FS_RENAME_DOES_D_MOVE 32768 /* FS will handle d_move() during rename() internally. */
struct dentry *(*mount) (struct file_system_type *, int,
const char *, void *);