fuse: separate fuse device allocation and installation in fuse_conn

As of now fuse_dev_alloc() both allocates a fuse device and installs it in
fuse_conn list.  fuse_dev_alloc() can fail if fuse_device allocation fails.

virtio-fs needs to initialize multiple fuse devices (one per virtio queue).
It initializes one fuse device as part of call to fuse_fill_super_common()
and rest of the devices are allocated and installed after that.

But, we can't afford to fail after calling fuse_fill_super_common() as we
don't have a way to undo all the actions done by fuse_fill_super_common().
So to avoid failures after the call to fuse_fill_super_common(),
pre-allocate all fuse devices early and install them into fuse connection
later.

This patch provides two separate helpers for fuse device allocation and
fuse device installation in fuse_conn.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

diff --git a/fs/fuse/cuse.c b/fs/fuse/cuse.c
index 6a0de0c..45762bb 100644 (file)
--- a/fs/fuse/cuse.c
+++ b/fs/fuse/cuse.c
@@ -508,7 +508,7 @@ static int cuse_channel_open(struct inode *inode, struct file *file)
         */
        fuse_conn_init(&cc->fc, file->f_cred->user_ns, &fuse_dev_fiq_ops, NULL);
 
-       fud = fuse_dev_alloc(&cc->fc);
+       fud = fuse_dev_alloc_install(&cc->fc);
        if (!fud) {
                kfree(cc);
                return -ENOMEM;

diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
index 358a014..b2e1886 100644 (file)
--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -2203,7 +2203,7 @@ static int fuse_device_clone(struct fuse_conn *fc, struct file *new)
        if (new->private_data)
                return -EINVAL;
 
-       fud = fuse_dev_alloc(fc);
+       fud = fuse_dev_alloc_install(fc);
        if (!fud)
                return -ENOMEM;
 

diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index 8c13865..242d477 100644 (file)
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -929,7 +929,9 @@ void fuse_conn_init(struct fuse_conn *fc, struct user_namespace *user_ns,
  */
 void fuse_conn_put(struct fuse_conn *fc);
 
-struct fuse_dev *fuse_dev_alloc(struct fuse_conn *fc);
+struct fuse_dev *fuse_dev_alloc_install(struct fuse_conn *fc);
+struct fuse_dev *fuse_dev_alloc(void);
+void fuse_dev_install(struct fuse_dev *fud, struct fuse_conn *fc);
 void fuse_dev_free(struct fuse_dev *fud);
 void fuse_send_init(struct fuse_conn *fc);
 

diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
index 734fdd5..6a0f31f 100644 (file)
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -1045,7 +1045,7 @@ static int fuse_bdi_init(struct fuse_conn *fc, struct super_block *sb)
        return 0;
 }
 
-struct fuse_dev *fuse_dev_alloc(struct fuse_conn *fc)
+struct fuse_dev *fuse_dev_alloc(void)
 {
        struct fuse_dev *fud;
        struct list_head *pq;
@@ -1061,16 +1061,33 @@ struct fuse_dev *fuse_dev_alloc(struct fuse_conn *fc)
        }
 
        fud->pq.processing = pq;
-       fud->fc = fuse_conn_get(fc);
        fuse_pqueue_init(&fud->pq);
 
+       return fud;
+}
+EXPORT_SYMBOL_GPL(fuse_dev_alloc);
+
+void fuse_dev_install(struct fuse_dev *fud, struct fuse_conn *fc)
+{
+       fud->fc = fuse_conn_get(fc);
        spin_lock(&fc->lock);
        list_add_tail(&fud->entry, &fc->devices);
        spin_unlock(&fc->lock);
+}
+EXPORT_SYMBOL_GPL(fuse_dev_install);
 
+struct fuse_dev *fuse_dev_alloc_install(struct fuse_conn *fc)
+{
+       struct fuse_dev *fud;
+
+       fud = fuse_dev_alloc();
+       if (!fud)
+               return NULL;
+
+       fuse_dev_install(fud, fc);
        return fud;
 }
-EXPORT_SYMBOL_GPL(fuse_dev_alloc);
+EXPORT_SYMBOL_GPL(fuse_dev_alloc_install);
 
 void fuse_dev_free(struct fuse_dev *fud)
 {
@@ -1132,7 +1149,7 @@ int fuse_fill_super_common(struct super_block *sb, struct fuse_fs_context *ctx)
        if (sb->s_user_ns != &init_user_ns)
                sb->s_xattr = fuse_no_acl_xattr_handlers;
 
-       fud = fuse_dev_alloc(fc);
+       fud = fuse_dev_alloc_install(fc);
        if (!fud)
                goto err;