Commit a8dd5f1b authored by Miklos Szeredi's avatar Miklos Szeredi
Browse files

fuse: create fuse_dev on /dev/fuse open instead of mount 



Allocate struct fuse_dev when opening the device.  This means that unlike
before, ->private_data is always set to a valid pointer.

The use of USE_DEV_SYNC_INIT magic pointer for the private_data is now
replaced with a simple bool sync_init member.

If sync INIT is not set, I/O on the device returns error before mount.
Keep this behavior by checking for the ->fc member.  If fud->fc is set, the
mount has succeeded.  Testing this used READ_ONCE(file->private_data) and
smp_mb() to try and provide the necessary semantics.  Switch this to
smp_store_release() and smp_load_acquire().

Setting fud->fc is protected by fuse_mutex, this is unchanged.

Will need this later so the /dev/fuse open file reference is not held
during FSCONFIG_CMD_CREATE.

Signed-off-by: default avatarMiklos Szeredi <mszeredi@redhat.com>
Reviewed-by: default avatar"Darrick J. Wong" <djwong@kernel.org>
parent e45f591f

fs/fuse/dev.c

+18 −29
Original line number Diff line number Diff line
@@ -1548,32 +1548,24 @@ static ssize_t fuse_dev_do_read(struct fuse_dev *fud, struct file *file, 


static int fuse_dev_open(struct inode *inode, struct file *file)

{

	/*

	 * The fuse device's file's private_data is used to hold

	 * the fuse_conn(ection) when it is mounted, and is used to

	 * keep track of whether the file has been mounted already.

	 */

	file->private_data = NULL;

	struct fuse_dev *fud = fuse_dev_alloc();



	if (!fud)

		return -ENOMEM;



	file->private_data = fud;

	return 0;

}



struct fuse_dev *fuse_get_dev(struct file *file)

{

	struct fuse_dev *fud = __fuse_get_dev(file);

	struct fuse_dev *fud = fuse_file_to_fud(file);

	int err;



	if (likely(fud))

		return fud;



	err = wait_event_interruptible(fuse_dev_waitq,

				       READ_ONCE(file->private_data) != FUSE_DEV_SYNC_INIT);

	err = wait_event_interruptible(fuse_dev_waitq, fuse_dev_fc_get(fud) != NULL);

	if (err)

		return ERR_PTR(err);



	fud = __fuse_get_dev(file);

	if (!fud)

		return ERR_PTR(-EPERM);



	return fud;

}
@@ -2547,10 +2539,10 @@ void fuse_wait_aborted(struct fuse_conn *fc) 


int fuse_dev_release(struct inode *inode, struct file *file)

{

	struct fuse_dev *fud = __fuse_get_dev(file);

	struct fuse_dev *fud = fuse_file_to_fud(file);

	struct fuse_conn *fc = fuse_dev_fc_get(fud);



	if (fud) {

		struct fuse_conn *fc = fud->fc;

	if (fc) {

		struct fuse_pqueue *fpq = &fud->pq;

		LIST_HEAD(to_end);

		unsigned int i;
@@ -2568,8 +2560,8 @@ int fuse_dev_release(struct inode *inode, struct file *file) 
			WARN_ON(fc->iq.fasync != NULL);

			fuse_abort_conn(fc);

		}

		fuse_dev_free(fud);

	}

	fuse_dev_free(fud);

	return 0;

}

EXPORT_SYMBOL_GPL(fuse_dev_release);
@@ -2587,16 +2579,12 @@ static int fuse_dev_fasync(int fd, struct file *file, int on) 


static int fuse_device_clone(struct fuse_conn *fc, struct file *new)

{

	struct fuse_dev *fud;

	struct fuse_dev *new_fud = fuse_file_to_fud(new);



	if (__fuse_get_dev(new))

	if (fuse_dev_fc_get(new_fud))

		return -EINVAL;



	fud = fuse_dev_alloc_install(fc);

	if (!fud)

		return -ENOMEM;



	new->private_data = fud;

	fuse_dev_install(new_fud, fc);

	atomic_inc(&fc->dev_count);



	return 0;
@@ -2667,10 +2655,11 @@ static long fuse_dev_ioctl_backing_close(struct file *file, __u32 __user *argp) 
static long fuse_dev_ioctl_sync_init(struct file *file)

{

	int err = -EINVAL;

	struct fuse_dev *fud = fuse_file_to_fud(file);



	mutex_lock(&fuse_mutex);

	if (!__fuse_get_dev(file)) {

		WRITE_ONCE(file->private_data, FUSE_DEV_SYNC_INIT);

	if (!fuse_dev_fc_get(fud)) {

		fud->sync_init = true;

		err = 0;

	}

	mutex_unlock(&fuse_mutex);

fs/fuse/fuse_dev_i.h

+25 −8
Original line number Diff line number Diff line
@@ -39,18 +39,35 @@ struct fuse_copy_state { 
	} ring;

};



#define FUSE_DEV_SYNC_INIT ((struct fuse_dev *) 1)

#define FUSE_DEV_PTR_MASK (~1UL)

/*

 * Lockless access is OK, because fud->fc is set once during mount and is valid

 * until the file is released.

 */

static inline struct fuse_conn *fuse_dev_fc_get(struct fuse_dev *fud)

{

	/* Pairs with smp_store_release() in fuse_dev_fc_set() */

	return smp_load_acquire(&fud->fc);

}



static inline void fuse_dev_fc_set(struct fuse_dev *fud, struct fuse_conn *fc)

{

	/* Pairs with smp_load_acquire() in fuse_dev_fc_get() */

	smp_store_release(&fud->fc, fc);

}



static inline struct fuse_dev *fuse_file_to_fud(struct file *file)

{

	return file->private_data;

}



static inline struct fuse_dev *__fuse_get_dev(struct file *file)

{

	/*

	 * Lockless access is OK, because file->private data is set

	 * once during mount and is valid until the file is released.

	 */

	struct fuse_dev *fud = READ_ONCE(file->private_data);

	struct fuse_dev *fud = fuse_file_to_fud(file);



	if (!fuse_dev_fc_get(fud))

		return NULL;



	return (typeof(fud)) ((unsigned long) fud & FUSE_DEV_PTR_MASK);

	return fud;

}



struct fuse_dev *fuse_get_dev(struct file *file);

fs/fuse/fuse_i.h

+3 −3
Original line number Diff line number Diff line
@@ -577,6 +577,9 @@ struct fuse_pqueue { 
 * Fuse device instance

 */

struct fuse_dev {

	/** Issue FUSE_INIT synchronously */

	bool sync_init;



	/** Fuse connection for this device */

	struct fuse_conn *fc;
@@ -623,9 +626,6 @@ struct fuse_fs_context { 


	/* DAX device, may be NULL */

	struct dax_device *dax_dev;



	/* fuse_dev pointer to fill in, should contain NULL on entry */

	void **fudptr;

};



struct fuse_sync_bucket {

fs/fuse/inode.c

+11 −24
Original line number Diff line number Diff line
@@ -1641,7 +1641,7 @@ EXPORT_SYMBOL_GPL(fuse_dev_alloc); 


void fuse_dev_install(struct fuse_dev *fud, struct fuse_conn *fc)

{

	fud->fc = fuse_conn_get(fc);

	fuse_dev_fc_set(fud, fuse_conn_get(fc));

	spin_lock(&fc->lock);

	list_add_tail(&fud->entry, &fc->devices);

	spin_unlock(&fc->lock);
@@ -1663,7 +1663,7 @@ EXPORT_SYMBOL_GPL(fuse_dev_alloc_install); 


void fuse_dev_free(struct fuse_dev *fud)

{

	struct fuse_conn *fc = fud->fc;

	struct fuse_conn *fc = fuse_dev_fc_get(fud);



	if (fc) {

		spin_lock(&fc->lock);
@@ -1826,7 +1826,7 @@ EXPORT_SYMBOL_GPL(fuse_init_fs_context_submount); 


int fuse_fill_super_common(struct super_block *sb, struct fuse_fs_context *ctx)

{

	struct fuse_dev *fud = NULL;

	struct fuse_dev *fud = ctx->file ? fuse_file_to_fud(ctx->file) : NULL;

	struct fuse_mount *fm = get_fuse_mount_super(sb);

	struct fuse_conn *fc = fm->fc;

	struct inode *root;
@@ -1860,18 +1860,11 @@ int fuse_fill_super_common(struct super_block *sb, struct fuse_fs_context *ctx) 
			goto err;

	}



	if (ctx->fudptr) {

		err = -ENOMEM;

		fud = fuse_dev_alloc_install(fc);

		if (!fud)

			goto err_free_dax;

	}



	fc->dev = sb->s_dev;

	fm->sb = sb;

	err = fuse_bdi_init(fc, sb);

	if (err)

		goto err_dev_free;

		goto err_free_dax;



	/* Handle umasking inside the fuse code */

	if (sb->s_flags & SB_POSIXACL)
@@ -1893,15 +1886,15 @@ int fuse_fill_super_common(struct super_block *sb, struct fuse_fs_context *ctx) 
	set_default_d_op(sb, &fuse_dentry_operations);

	root_dentry = d_make_root(root);

	if (!root_dentry)

		goto err_dev_free;

		goto err_free_dax;



	mutex_lock(&fuse_mutex);

	err = -EINVAL;

	if (ctx->fudptr && *ctx->fudptr) {

		if (*ctx->fudptr == FUSE_DEV_SYNC_INIT)

			fc->sync_init = 1;

		else

	if (fud) {

		if (fuse_dev_fc_get(fud))

			goto err_unlock;

		if (fud->sync_init)

			fc->sync_init = 1;

	}



	err = fuse_ctl_add_conn(fc);
@@ -1910,8 +1903,8 @@ int fuse_fill_super_common(struct super_block *sb, struct fuse_fs_context *ctx) 


	list_add_tail(&fc->entry, &fuse_conn_list);

	sb->s_root = root_dentry;

	if (ctx->fudptr) {

		*ctx->fudptr = fud;

	if (fud) {

		fuse_dev_install(fud, fc);

		wake_up_all(&fuse_dev_waitq);

	}

	mutex_unlock(&fuse_mutex);
@@ -1920,9 +1913,6 @@ int fuse_fill_super_common(struct super_block *sb, struct fuse_fs_context *ctx) 
 err_unlock:

	mutex_unlock(&fuse_mutex);

	dput(root_dentry);

 err_dev_free:

	if (fud)

		fuse_dev_free(fud);

 err_free_dax:

	if (IS_ENABLED(CONFIG_FUSE_DAX))

		fuse_dax_conn_free(fc);
@@ -1948,13 +1938,10 @@ static int fuse_fill_super(struct super_block *sb, struct fs_context *fsc) 
	if ((ctx->file->f_op != &fuse_dev_operations) ||

	    (ctx->file->f_cred->user_ns != sb->s_user_ns))

		return -EINVAL;

	ctx->fudptr = &ctx->file->private_data;



	err = fuse_fill_super_common(sb, ctx);

	if (err)

		return err;

	/* file->private_data shall be visible on all CPUs after this */

	smp_mb();



	fm = get_fuse_mount_super(sb);

fs/fuse/virtio_fs.c

+0 −2
Original line number Diff line number Diff line
@@ -1590,8 +1590,6 @@ static int virtio_fs_fill_super(struct super_block *sb, struct fs_context *fsc) 
			goto err_free_fuse_devs;

	}



	/* virtiofs allocates and installs its own fuse devices */

	ctx->fudptr = NULL;

	if (ctx->dax_mode != FUSE_DAX_NEVER) {

		if (ctx->dax_mode == FUSE_DAX_ALWAYS && !fs->dax_dev) {

			err = -EINVAL;