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

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

[Andy Whitcroft]

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!

This is triggered by statfs when calculating the free space in the
filesytem.  We bug if the number of read/write devices is 0.

This check seems spurious as the information collected is valid regardless
of whether the devices are read-only or not.  As the count is used to
size the sort array it seems more correct to switch it to the number of
open devices.

BugLink: http://bugs.launchpad.net/bugs/816770
Signed-off-by: Andy Whitcroft <apw@canonical.com>
---
 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

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

[Josef Bacik]

On 08/01/2011 09:38 AM, 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!
> 
> This is triggered by statfs when calculating the free space in the
> filesytem.  We bug if the number of read/write devices is 0.
> 
> This check seems spurious as the information collected is valid regardless
> of whether the devices are read-only or not.  As the count is used to
> size the sort array it seems more correct to switch it to the number of
> open devices.
> 
> BugLink: http://bugs.launchpad.net/bugs/816770
> Signed-off-by: Andy Whitcroft <apw@canonical.com>

Acked-by: Josef Bacik <josef@redhat.com>

Thanks,

Josef

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

[Jonathan Nieder]

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?

>  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
>

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

[Andy Whitcroft]

On Mon, Nov 28, 2011 at 06:11:06AM -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 had completely forgotten about this one.  I wonder where it did get
to.  I seem to remember testing this in house successfully.

-apw

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

[Li Zefan]

Andy Whitcroft wrote:
> On Mon, Nov 28, 2011 at 06:11:06AM -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 had completely forgotten about this one.  I wonder where it did get
> to.  I seem to remember testing this in house successfully.
> 

This patch has the same problem with your previous one, that it will set
f_bavail to 0. I've sent out a new patch yesterday.

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

[Jonathan Nieder]

Li Zefan wrote:

> This patch has the same problem with your previous one, that it will set
> f_bavail to 0. I've sent out a new patch yesterday.

Thanks for the quick feedback.  That makes sense.  (The new patch
is at [1], for reference.)

[1] http://thread.gmane.org/gmane.comp.file-systems.btrfs/14584

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

[Andy Whitcroft]

On Tue, Nov 29, 2011 at 09:26:01AM +0800, Li Zefan wrote:

> This patch has the same problem with your previous one, that it will set
> f_bavail to 0. I've sent out a new patch yesterday.

Ahh, sounds great thanks.  Often a patch is a good way to start a
discussion to a more correct patch.  Specially when one is not an expert
in the area.

-apw

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

[Miao Xie]

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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