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Btrfs: Fix uninitialized root flags for subvolumes

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root_item->flags and root_item->byte_limit are not initialized when
a subvolume is created. This bug is not revealed until we added
readonly snapshot support - now you mount a btrfs filesystem and you
may find the subvolumes in it are readonly.

To work around this problem, we steal a bit from root_item->inode_item->flags,
and use it to indicate if those fields have been properly initialized.
When we read a tree root from disk, we check if the bit is set, and if
not we'll set the flag and initialize the two fields of the root item.

Reported-by: Andreas Philipp <philipp.andreas@gmail.com>
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Tested-by: Andreas Philipp <philipp.andreas@gmail.com>
cc: stable@kernel.org
Signed-off-by: Chris Mason <chris.mason@oracle.com>
This commit is contained in:
Li Zefan 2011-03-28 02:01:25 +00:00 • committed by Chris Mason
parent adae52b94e
commit 08fe4db170
5 changed files with 30 additions and 1 deletions
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18
fs/btrfs/root-tree.c
View file

@ -473,3 +473,21 @@ again:
btrfs_free_path(path);
return 0;
}
/*
* Old btrfs forgets to init root_item->flags and root_item->byte_limit
* for subvolumes. To work around this problem, we steal a bit from
* root_item->inode_item->flags, and use it to indicate if those fields
* have been properly initialized.
*/
void btrfs_check_and_init_root_item(struct btrfs_root_item *root_item)
{
u64 inode_flags = le64_to_cpu(root_item->inode.flags);
if (!(inode_flags & BTRFS_INODE_ROOT_ITEM_INIT)) {
inode_flags |= BTRFS_INODE_ROOT_ITEM_INIT;
root_item->inode.flags = cpu_to_le64(inode_flags);
root_item->flags = 0;
root_item->byte_limit = 0;
}
}