[PATCH] fuse: support caching negative dentries

Add support for caching negative dentries.

Up till now, ->d_revalidate() always forced a new lookup on these.  Now let
the lookup method return a zero node ID (not used for anything else) meaning a
negative entry, but with a positive cache timeout.  The old way of signaling
negative entry (replying ENOENT) still works.

Userspace should check the ABI minor version to see whether sending a zero ID
is allowed by the kernel or not.

Signed-off-by: Miklos Szeredi <miklos@szeredi.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 43 insertions, 21 deletions

diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c
index 0d1438a9dab3..4c127f2bc814 100644
--- a/fs/fuse/dir.c
+++ b/fs/fuse/dir.c
@@ -23,9 +23,26 @@ static inline unsigned long time_to_jiffies(unsigned long sec,
 
 static void fuse_change_timeout(struct dentry *entry, struct fuse_entry_out *o)
 {
-        struct fuse_inode *fi = get_fuse_inode(entry->d_inode);
         entry->d_time = time_to_jiffies(o->entry_valid, o->entry_valid_nsec);
-        fi->i_time = time_to_jiffies(o->attr_valid, o->attr_valid_nsec);
+        if (entry->d_inode)
+                get_fuse_inode(entry->d_inode)->i_time =
+                        time_to_jiffies(o->attr_valid, o->attr_valid_nsec);
+}
+
+void fuse_invalidate_attr(struct inode *inode)
+{
+        get_fuse_inode(inode)->i_time = jiffies - 1;
+}
+
+static void fuse_invalidate_entry_cache(struct dentry *entry)
+{
+        entry->d_time = jiffies - 1;
+}
+
+static void fuse_invalidate_entry(struct dentry *entry)
+{
+        d_invalidate(entry);
+        fuse_invalidate_entry_cache(entry);
 }
 
 static void fuse_lookup_init(struct fuse_req *req, struct inode *dir,
@@ -45,15 +62,22 @@ static void fuse_lookup_init(struct fuse_req *req, struct inode *dir,
 
 static int fuse_dentry_revalidate(struct dentry *entry, struct nameidata *nd)
 {
-        if (!entry->d_inode || is_bad_inode(entry->d_inode))
+        struct inode *inode = entry->d_inode;
+
+        if (inode && is_bad_inode(inode))
                 return 0;
         else if (time_after(jiffies, entry->d_time)) {
                 int err;
                 struct fuse_entry_out outarg;
-                struct inode *inode = entry->d_inode;
-                struct fuse_inode *fi = get_fuse_inode(inode);
-                struct fuse_conn *fc = get_fuse_conn(inode);
-                struct fuse_req *req = fuse_get_request(fc);
+                struct fuse_conn *fc;
+                struct fuse_req *req;
+
+                fuse_invalidate_entry_cache(entry);
+                if (!inode)
+                        return 0;
+
+                fc = get_fuse_conn(inode);
+                req = fuse_get_request(fc);
                 if (!req)
                         return 0;
 
@@ -61,6 +85,7 @@ static int fuse_dentry_revalidate(struct dentry *entry, struct nameidata *nd)
                 request_send(fc, req);
                 err = req->out.h.error;
                 if (!err) {
+                        struct fuse_inode *fi = get_fuse_inode(inode);
                         if (outarg.nodeid != get_node_id(inode)) {
                                 fuse_send_forget(fc, req, outarg.nodeid, 1);
                                 return 0;
@@ -118,9 +143,9 @@ static struct dentry *fuse_lookup(struct inode *dir, struct dentry *entry,
         fuse_lookup_init(req, dir, entry, &outarg);
         request_send(fc, req);
         err = req->out.h.error;
-        if (!err && invalid_nodeid(outarg.nodeid))
+        if (!err && outarg.nodeid && invalid_nodeid(outarg.nodeid))
                 err = -EIO;
-        if (!err) {
+        if (!err && outarg.nodeid) {
                 inode = fuse_iget(dir->i_sb, outarg.nodeid, outarg.generation,
                                   &outarg.attr);
                 if (!inode) {
@@ -138,22 +163,13 @@ static struct dentry *fuse_lookup(struct inode *dir, struct dentry *entry,
         }
         d_add(entry, inode);
         entry->d_op = &fuse_dentry_operations;
-        if (inode)
+        if (!err)
                 fuse_change_timeout(entry, &outarg);
+        else
+                fuse_invalidate_entry_cache(entry);
         return NULL;
 }
 
-void fuse_invalidate_attr(struct inode *inode)
-{
-        get_fuse_inode(inode)->i_time = jiffies - 1;
-}
-
-static void fuse_invalidate_entry(struct dentry *entry)
-{
-        d_invalidate(entry);
-        entry->d_time = jiffies - 1;
-}
-
 static int fuse_create_open(struct inode *dir, struct dentry *entry, int mode,
                             struct nameidata *nd)
 {
@@ -387,6 +403,7 @@ static int fuse_unlink(struct inode *dir, struct dentry *entry)
                 inode->i_nlink = 0;
                 fuse_invalidate_attr(inode);
                 fuse_invalidate_attr(dir);
+                fuse_invalidate_entry_cache(entry);
         } else if (err == -EINTR)
                 fuse_invalidate_entry(entry);
         return err;
@@ -412,6 +429,7 @@ static int fuse_rmdir(struct inode *dir, struct dentry *entry)
         if (!err) {
                 entry->d_inode->i_nlink = 0;
                 fuse_invalidate_attr(dir);
+                fuse_invalidate_entry_cache(entry);
         } else if (err == -EINTR)
                 fuse_invalidate_entry(entry);
         return err;
@@ -447,6 +465,10 @@ static int fuse_rename(struct inode *olddir, struct dentry *oldent,
                 fuse_invalidate_attr(olddir);
                 if (olddir != newdir)
                         fuse_invalidate_attr(newdir);
+
+                /* newent will end up negative */
+                if (newent->d_inode)
+                        fuse_invalidate_entry_cache(newent);
         } else if (err == -EINTR) {
                 /* If request was interrupted, DEITY only knows if the
                    rename actually took place.  If the invalidation