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Btrfs: setup blank root and fs_info for mount time

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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: Josef Bacik <josef@redhat.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>
This commit is contained in:
Josef Bacik 2010-11-19 14:59:15 -05:00 committed by Chris Mason
parent 975f84fee2
commit 450ba0ea06
2 changed files with 33 additions and 7 deletions
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6
fs/btrfs/disk-io.c
View File

@ -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),

34
fs/btrfs/super.c
View File

@ -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;