[PATCH] FUSE: add access call

Add a new access call, which will only be called if ->permission is invoked
from sys_access().  In all other cases permission checking is delayed until
the actual filesystem operation.

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

3 files changed, 45 insertions, 1 deletions

diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c
index 61b58fdd973e..4bc1afcc476d 100644
--- a/fs/fuse/dir.c
+++ b/fs/fuse/dir.c
@@ -461,6 +461,38 @@ static int fuse_revalidate(struct dentry *entry)
         return fuse_do_getattr(inode);
 }
 
+static int fuse_access(struct inode *inode, int mask)
+{
+        struct fuse_conn *fc = get_fuse_conn(inode);
+        struct fuse_req *req;
+        struct fuse_access_in inarg;
+        int err;
+
+        if (fc->no_access)
+                return 0;
+
+        req = fuse_get_request(fc);
+        if (!req)
+                return -EINTR;
+
+        memset(&inarg, 0, sizeof(inarg));
+        inarg.mask = mask;
+        req->in.h.opcode = FUSE_ACCESS;
+        req->in.h.nodeid = get_node_id(inode);
+        req->inode = inode;
+        req->in.numargs = 1;
+        req->in.args[0].size = sizeof(inarg);
+        req->in.args[0].value = &inarg;
+        request_send(fc, req);
+        err = req->out.h.error;
+        fuse_put_request(fc, req);
+        if (err == -ENOSYS) {
+                fc->no_access = 1;
+                err = 0;
+        }
+        return err;
+}
+
 static int fuse_permission(struct inode *inode, int mask, struct nameidata *nd)
 {
         struct fuse_conn *fc = get_fuse_conn(inode);
@@ -493,6 +525,9 @@ static int fuse_permission(struct inode *inode, int mask, struct nameidata *nd)
                 int mode = inode->i_mode;
                 if ((mask & MAY_EXEC) && !S_ISDIR(mode) && !(mode & S_IXUGO))
                         return -EACCES;
+
+                if (nd && (nd->flags & LOOKUP_ACCESS))
+                        return fuse_access(inode, mask);
                 return 0;
         }
 }
diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index 5cb456f572c1..c4e8c3b47982 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -266,6 +266,9 @@ struct fuse_conn {
         /** Is removexattr not implemented by fs? */
         unsigned no_removexattr : 1;
 
+        /** Is access not implemented by fs? */
+        unsigned no_access : 1;
+
         /** Backing dev info */
         struct backing_dev_info bdi;
 };
diff --git a/include/linux/fuse.h b/include/linux/fuse.h
index 6e91c9a3a0b6..507913b65af0 100644
--- a/include/linux/fuse.h
+++ b/include/linux/fuse.h
@@ -99,7 +99,8 @@ enum fuse_opcode {
         FUSE_OPENDIR       = 27,
         FUSE_READDIR       = 28,
         FUSE_RELEASEDIR    = 29,
-        FUSE_FSYNCDIR      = 30
+        FUSE_FSYNCDIR      = 30,
+        FUSE_ACCESS        = 34
 };
 
 /* Conservative buffer size for the client */
@@ -222,6 +223,11 @@ struct fuse_getxattr_out {
         __u32   padding;
 };
 
+struct fuse_access_in {
+        __u32   mask;
+        __u32   padding;
+};
+
 struct fuse_init_in_out {
         __u32   major;
         __u32   minor;