Re: [PATCH 1/1] btrfs: btrfs_calc_avail_data_space cope with no read/write devices V2

Miao Xie
2011-11-29T01:56:15Z

On mon, 28 Nov 2011 06:11:06 -0600, Jonathan Nieder wrote:
> Hi,
>
> Andy Whitcroft wrote:
>
>> When we mount a btrfs filesystem from read-only media there will be no
>> read/write devices; for example mounting an SD card with its lock enabled.
>> This triggers an immediate BUG during mount:
>>
>> kernel BUG at .../fs/btrfs/super.c:984!
> [...]
>> BugLink: http://bugs.launchpad.net/bugs/816770
>> Signed-off-by: Andy Whitcroft <apw@canonical.com>
>> ---
>
> Fixes http://bugs.debian.org/649847
> Tested-by: Ivan Vilata i Balaguer <ivan@selidor.net>
>
> This patch fixes a regression introduced by 6d07bcec969a ("btrfs: fix
> wrong free space information of btrfs"), which hit mainline in
> v2.6.38-rc1. Josef Bacik acked the patch, but I can't seem to find it
> in linux-next, linux-btrfs, or Josef's btrfs-work tree. Maybe it was
> just forgotten.
>
> What can I do to help this patch get unstuck?

I think We should make this behaviour similar to the traditional file systems,
such as ext3/4. That is the available space should show the size of all the free space
which we may used to store the file data, even we mount it on the read-only mode.
This patch didn't fix the problem completely.

Thanks
Miao

>> fs/btrfs/super.c | 2 +-
>> 1 files changed, 1 insertions(+), 1 deletions(-)
>>
>> diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
>> index 15634d4..ae4367a 100644
>> --- a/fs/btrfs/super.c
>> +++ b/fs/btrfs/super.c
>> @@ -980,7 +980,7 @@ static int btrfs_calc_avail_data_space(struct btrfs_root *root, u64 *free_bytes)
>> int i = 0, nr_devices;
>> int ret;
>>
>> - nr_devices = fs_info->fs_devices->rw_devices;
>> + nr_devices = fs_info->fs_devices->open_devices;
>> BUG_ON(!nr_devices);
>>
>> devices_info = kmalloc(sizeof(*devices_info) * nr_devices,
>> --
>> 1.7.4.1
>>
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