[PATCH v2 10/30] fuse: Separate fuse device allocation and installation in fuse_conn

Vivek Goyal
2019-05-15T19:30:49Z

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 affort 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>
---
fs/fuse/cuse.c | 2 +-
fs/fuse/dev.c | 2 +-
fs/fuse/fuse_i.h | 4 +++-
fs/fuse/inode.c | 25 ++++++++++++++++++++-----
4 files changed, 25 insertions(+), 8 deletions(-)

diff --git a/fs/fuse/cuse.c b/fs/fuse/cuse.c
index a6ed7a036b50..a509747153a7 100644
--- a/fs/fuse/cuse.c
+++ b/fs/fuse/cuse.c
@@ -506,7 +506,7 @@ 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 ef489beadf58..ee9dd38bc0f0 100644
--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -2318,7 +2318,7 @@ 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 0b578e07156d..4008ed65a48d 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -1050,7 +1050,9 @@ 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, struct fuse_req *req);

diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
index 126e77854dac..9b0114437a14 100644
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -1027,8 +1027,7 @@ 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;

@@ -1043,16 +1042,32 @@ 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)
{
@@ -1122,7 +1137,7 @@ int fuse_fill_super_common(struct super_block *sb,
mount_data->fiq_priv);
fc->release = fuse_free_conn;

- fud = fuse_dev_alloc(fc);
+ fud = fuse_dev_alloc_install(fc);
if (!fud)
goto err_put_conn;

--
2.20.1