fuse: implement open in passthrough mode

[linux-2.6-block.git] / fs / fuse / passthrough.c

diff --git a/fs/fuse/passthrough.c b/fs/fuse/passthrough.c
index 7ec92a54c2e0c24b704edf661f296ec9da545c40..dc054d2ab13e62d4732a01ac44e170b86c1ae090 100644 (file)
--- a/fs/fuse/passthrough.c
+++ b/fs/fuse/passthrough.c
@@ -8,6 +8,7 @@
 #include "fuse_i.h"
 
 #include <linux/file.h>
+#include <linux/backing-file.h>
 
 struct fuse_backing *fuse_backing_get(struct fuse_backing *fb)
 {
@@ -164,3 +165,61 @@ out:
 
        return err;
 }
+
+/*
+ * Setup passthrough to a backing file.
+ *
+ * Returns an fb object with elevated refcount to be stored in fuse inode.
+ */
+struct fuse_backing *fuse_passthrough_open(struct file *file,
+                                          struct inode *inode,
+                                          int backing_id)
+{
+       struct fuse_file *ff = file->private_data;
+       struct fuse_conn *fc = ff->fm->fc;
+       struct fuse_backing *fb = NULL;
+       struct file *backing_file;
+       int err;
+
+       err = -EINVAL;
+       if (backing_id <= 0)
+               goto out;
+
+       rcu_read_lock();
+       fb = idr_find(&fc->backing_files_map, backing_id);
+       fb = fuse_backing_get(fb);
+       rcu_read_unlock();
+
+       err = -ENOENT;
+       if (!fb)
+               goto out;
+
+       /* Allocate backing file per fuse file to store fuse path */
+       backing_file = backing_file_open(&file->f_path, file->f_flags,
+                                        &fb->file->f_path, fb->cred);
+       err = PTR_ERR(backing_file);
+       if (IS_ERR(backing_file)) {
+               fuse_backing_put(fb);
+               goto out;
+       }
+
+       err = 0;
+       ff->passthrough = backing_file;
+       ff->cred = get_cred(fb->cred);
+out:
+       pr_debug("%s: backing_id=%d, fb=0x%p, backing_file=0x%p, err=%i\n", __func__,
+                backing_id, fb, ff->passthrough, err);
+
+       return err ? ERR_PTR(err) : fb;
+}
+
+void fuse_passthrough_release(struct fuse_file *ff, struct fuse_backing *fb)
+{
+       pr_debug("%s: fb=0x%p, backing_file=0x%p\n", __func__,
+                fb, ff->passthrough);
+
+       fput(ff->passthrough);
+       ff->passthrough = NULL;
+       put_cred(ff->cred);
+       ff->cred = NULL;
+}