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authorDavid Howells <dhowells@redhat.com>2019-05-20 08:48:46 +0100
committerDavid Howells <dhowells@redhat.com>2019-09-02 11:43:54 +0100
commita0753c29004f4983e303abce019f29e183b1ee48 (patch)
tree0227fe9742afaf92caddb7e5f086cf5f474becf0 /fs/afs/dir.c
parent8b6a666a97544bf307190a05947742b8357aa962 (diff)
downloadlinux-a0753c29004f4983e303abce019f29e183b1ee48.tar.bz2
afs: Support RCU pathwalk
Make afs_permission() and afs_d_revalidate() do initial checks in RCU-mode pathwalk to reduce latency in pathwalk elements that get done multiple times. We don't need to query the server unless we've received a notification from it that something has changed or the callback has expired. This requires that we can request a key and check permits under RCU conditions if we need to. Signed-off-by: David Howells <dhowells@redhat.com>
Diffstat (limited to 'fs/afs/dir.c')
-rw-r--r--fs/afs/dir.c54
1 files changed, 53 insertions, 1 deletions
diff --git a/fs/afs/dir.c b/fs/afs/dir.c
index 139b4e3cc946..cc12772d0a4d 100644
--- a/fs/afs/dir.c
+++ b/fs/afs/dir.c
@@ -966,6 +966,58 @@ static struct dentry *afs_lookup(struct inode *dir, struct dentry *dentry,
}
/*
+ * Check the validity of a dentry under RCU conditions.
+ */
+static int afs_d_revalidate_rcu(struct dentry *dentry)
+{
+ struct afs_vnode *dvnode, *vnode;
+ struct dentry *parent;
+ struct inode *dir, *inode;
+ long dir_version, de_version;
+
+ _enter("%p", dentry);
+
+ /* Check the parent directory is still valid first. */
+ parent = READ_ONCE(dentry->d_parent);
+ dir = d_inode_rcu(parent);
+ if (!dir)
+ return -ECHILD;
+ dvnode = AFS_FS_I(dir);
+ if (test_bit(AFS_VNODE_DELETED, &dvnode->flags))
+ return -ECHILD;
+
+ if (!afs_check_validity(dvnode))
+ return -ECHILD;
+
+ /* We only need to invalidate a dentry if the server's copy changed
+ * behind our back. If we made the change, it's no problem. Note that
+ * on a 32-bit system, we only have 32 bits in the dentry to store the
+ * version.
+ */
+ dir_version = (long)READ_ONCE(dvnode->status.data_version);
+ de_version = (long)READ_ONCE(dentry->d_fsdata);
+ if (de_version != dir_version) {
+ dir_version = (long)READ_ONCE(dvnode->invalid_before);
+ if (de_version - dir_version < 0)
+ return -ECHILD;
+ }
+
+ /* Check to see if the vnode referred to by the dentry still
+ * has a callback.
+ */
+ if (d_really_is_positive(dentry)) {
+ inode = d_inode_rcu(dentry);
+ if (inode) {
+ vnode = AFS_FS_I(inode);
+ if (!afs_check_validity(vnode))
+ return -ECHILD;
+ }
+ }
+
+ return 1; /* Still valid */
+}
+
+/*
* check that a dentry lookup hit has found a valid entry
* - NOTE! the hit can be a negative hit too, so we can't assume we have an
* inode
@@ -982,7 +1034,7 @@ static int afs_d_revalidate(struct dentry *dentry, unsigned int flags)
int ret;
if (flags & LOOKUP_RCU)
- return -ECHILD;
+ return afs_d_revalidate_rcu(dentry);
if (d_really_is_positive(dentry)) {
vnode = AFS_FS_I(d_inode(dentry));