Commit 450ba0ea authored by Josef Bacik's avatar Josef Bacik Committed by Chris Mason
Browse files

Btrfs: setup blank root and fs_info for mount time 



There is a problem with how we use sget, it searches through the list of supers
attached to the fs_type looking for a super with the same fs_devices as what
we're trying to mount.  This depends on sb->s_fs_info being filled, but we don't
fill that in until we get to btrfs_fill_super, so we could hit supers on the
fs_type super list that have a null s_fs_info.  In order to fix that we need to
go ahead and setup a blank root with a blank fs_info to hold fs_devices, that
way our test will work out right and then we can set s_fs_info in
btrfs_set_super, and then open_ctree will simply use our pre-allocated root and
fs_info when setting everything up.  Thanks,

Signed-off-by: default avatarJosef Bacik <josef@redhat.com>
Signed-off-by: default avatarChris Mason <chris.mason@oracle.com>
parent 975f84fe

fs/btrfs/disk-io.c

+2 −4
Original line number Diff line number Diff line
@@ -1561,10 +1561,8 @@ struct btrfs_root *open_ctree(struct super_block *sb, 
						 GFP_NOFS);

	struct btrfs_root *csum_root = kzalloc(sizeof(struct btrfs_root),

						 GFP_NOFS);

	struct btrfs_root *tree_root = kzalloc(sizeof(struct btrfs_root),

					       GFP_NOFS);

	struct btrfs_fs_info *fs_info = kzalloc(sizeof(*fs_info),

						GFP_NOFS);

	struct btrfs_root *tree_root = btrfs_sb(sb);

	struct btrfs_fs_info *fs_info = tree_root->fs_info;

	struct btrfs_root *chunk_root = kzalloc(sizeof(struct btrfs_root),

						GFP_NOFS);

	struct btrfs_root *dev_root = kzalloc(sizeof(struct btrfs_root),

fs/btrfs/super.c

+31 −3
Original line number Diff line number Diff line
@@ -563,7 +563,7 @@ static int btrfs_show_options(struct seq_file *seq, struct vfsmount *vfs) 


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

{

	struct btrfs_fs_devices *test_fs_devices = data;

	struct btrfs_root *test_root = data;

	struct btrfs_root *root = btrfs_sb(s);



	/*
@@ -572,9 +572,17 @@ static int btrfs_test_super(struct super_block *s, void *data) 
	 */

	if (!atomic_read(&s->s_active))

		return 0;

	return root->fs_info->fs_devices == test_fs_devices;

	return root->fs_info->fs_devices == test_root->fs_info->fs_devices;

}



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

{

	s->s_fs_info = data;



	return set_anon_super(s, data);

}





/*

 * Find a superblock for the given device / mount point.

 *
@@ -588,6 +596,8 @@ static int btrfs_get_sb(struct file_system_type *fs_type, int flags, 
	struct super_block *s;

	struct dentry *root;

	struct btrfs_fs_devices *fs_devices = NULL;

	struct btrfs_root *tree_root = NULL;

	struct btrfs_fs_info *fs_info = NULL;

	fmode_t mode = FMODE_READ;

	char *subvol_name = NULL;

	u64 subvol_objectid = 0;
@@ -615,8 +625,24 @@ static int btrfs_get_sb(struct file_system_type *fs_type, int flags, 
		goto error_close_devices;

	}



	/*

	 * Setup a dummy root and fs_info for test/set super.  This is because

	 * we don't actually fill this stuff out until open_ctree, but we need

	 * it for searching for existing supers, so this lets us do that and

	 * then open_ctree will properly initialize everything later.

	 */

	fs_info = kzalloc(sizeof(struct btrfs_fs_info), GFP_NOFS);

	tree_root = kzalloc(sizeof(struct btrfs_root), GFP_NOFS);

	if (!fs_info || !tree_root) {

		error = -ENOMEM;

		goto error_close_devices;

	}

	fs_info->tree_root = tree_root;

	fs_info->fs_devices = fs_devices;

	tree_root->fs_info = fs_info;



	bdev = fs_devices->latest_bdev;

	s = sget(fs_type, btrfs_test_super, set_anon_super, fs_devices);

	s = sget(fs_type, btrfs_test_super, btrfs_set_super, tree_root);

	if (IS_ERR(s))

		goto error_s;
@@ -685,6 +711,8 @@ error_s: 
	error = PTR_ERR(s);

error_close_devices:

	btrfs_close_devices(fs_devices);

	kfree(fs_info);

	kfree(tree_root);

error_free_subvol_name:

	kfree(subvol_name);

	return error;

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