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Commit fe62c3a4 authored by David Howells's avatar David Howells Committed by Al Viro
Browse files

vfs: Create fs_context-aware mount_bdev() replacement 



Create a function, get_tree_bdev(), that is fs_context-aware and a
->get_tree() counterpart of mount_bdev().

It caches the block device pointer in the fs_context struct so that this
information can be passed into sget_fc()'s test and set functions.

Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
cc: Jens Axboe <axboe@kernel.dk>
cc: linux-block@vger.kernel.org
Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent 533770cc

fs/super.c

+94 −0
Original line number Diff line number Diff line
@@ -1222,6 +1222,7 @@ int get_tree_keyed(struct fs_context *fc, 
EXPORT_SYMBOL(get_tree_keyed);



#ifdef CONFIG_BLOCK



static int set_bdev_super(struct super_block *s, void *data)

{

	s->s_bdev = data;
@@ -1231,6 +1232,99 @@ static int set_bdev_super(struct super_block *s, void *data) 
	return 0;

}



static int set_bdev_super_fc(struct super_block *s, struct fs_context *fc)

{

	return set_bdev_super(s, fc->sget_key);

}



static int test_bdev_super_fc(struct super_block *s, struct fs_context *fc)

{

	return s->s_bdev == fc->sget_key;

}



/**

 * get_tree_bdev - Get a superblock based on a single block device

 * @fc: The filesystem context holding the parameters

 * @fill_super: Helper to initialise a new superblock

 */

int get_tree_bdev(struct fs_context *fc,

		int (*fill_super)(struct super_block *,

				  struct fs_context *))

{

	struct block_device *bdev;

	struct super_block *s;

	fmode_t mode = FMODE_READ | FMODE_EXCL;

	int error = 0;



	if (!(fc->sb_flags & SB_RDONLY))

		mode |= FMODE_WRITE;



	if (!fc->source)

		return invalf(fc, "No source specified");



	bdev = blkdev_get_by_path(fc->source, mode, fc->fs_type);

	if (IS_ERR(bdev)) {

		errorf(fc, "%s: Can't open blockdev", fc->source);

		return PTR_ERR(bdev);

	}



	/* Once the superblock is inserted into the list by sget_fc(), s_umount

	 * will protect the lockfs code from trying to start a snapshot while

	 * we are mounting

	 */

	mutex_lock(&bdev->bd_fsfreeze_mutex);

	if (bdev->bd_fsfreeze_count > 0) {

		mutex_unlock(&bdev->bd_fsfreeze_mutex);

		warnf(fc, "%pg: Can't mount, blockdev is frozen", bdev);

		return -EBUSY;

	}



	fc->sb_flags |= SB_NOSEC;

	fc->sget_key = bdev;

	s = sget_fc(fc, test_bdev_super_fc, set_bdev_super_fc);

	mutex_unlock(&bdev->bd_fsfreeze_mutex);

	if (IS_ERR(s))

		return PTR_ERR(s);



	if (s->s_root) {

		/* Don't summarily change the RO/RW state. */

		if ((fc->sb_flags ^ s->s_flags) & SB_RDONLY) {

			warnf(fc, "%pg: Can't mount, would change RO state", bdev);

			deactivate_locked_super(s);

			blkdev_put(bdev, mode);

			return -EBUSY;

		}



		/*

		 * s_umount nests inside bd_mutex during

		 * __invalidate_device().  blkdev_put() acquires

		 * bd_mutex and can't be called under s_umount.  Drop

		 * s_umount temporarily.  This is safe as we're

		 * holding an active reference.

		 */

		up_write(&s->s_umount);

		blkdev_put(bdev, mode);

		down_write(&s->s_umount);

	} else {

		s->s_mode = mode;

		snprintf(s->s_id, sizeof(s->s_id), "%pg", bdev);

		sb_set_blocksize(s, block_size(bdev));

		error = fill_super(s, fc);

		if (error) {

			deactivate_locked_super(s);

			return error;

		}



		s->s_flags |= SB_ACTIVE;

		bdev->bd_super = s;

	}



	BUG_ON(fc->root);

	fc->root = dget(s->s_root);

	return 0;

}

EXPORT_SYMBOL(get_tree_bdev);



static int test_bdev_super(struct super_block *s, void *data)

{

	return (void *)s->s_bdev == data;

include/linux/fs_context.h

+5 −0
Original line number Diff line number Diff line
@@ -88,6 +88,7 @@ struct fs_context { 
	struct mutex		uapi_mutex;	/* Userspace access mutex */

	struct file_system_type	*fs_type;

	void			*fs_private;	/* The filesystem's context */

	void			*sget_key;

	struct dentry		*root;		/* The root and superblock */

	struct user_namespace	*user_ns;	/* The user namespace for this mount */

	struct net		*net_ns;	/* The network namespace for this mount */
@@ -159,6 +160,10 @@ extern int get_tree_keyed(struct fs_context *fc, 
					   struct fs_context *fc),

			 void *key);



extern int get_tree_bdev(struct fs_context *fc,

			       int (*fill_super)(struct super_block *sb,

						 struct fs_context *fc));



extern const struct file_operations fscontext_fops;



/*