[PATCH] Btrfs: disable snapshot aware defrag for now

[PATCH] Btrfs: disable snapshot aware defrag for now

[Josef Bacik]

It's just broken and it's taking a lot of effort to fix it, so for now just
disable it so people can defrag in peace.  Thanks,

Cc: stable@vger.kernel.org
Signed-off-by: Josef Bacik <jbacik@fb.com>
---
 fs/btrfs/inode.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 3b65987..8c0bc31 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -2628,7 +2628,7 @@ static int btrfs_finish_ordered_io(struct btrfs_ordered_extent *ordered_extent)
 			EXTENT_DEFRAG, 1, cached_state);
 	if (ret) {
 		u64 last_snapshot = btrfs_root_last_snapshot(&root->root_item);
-		if (last_snapshot >= BTRFS_I(inode)->generation)
+		if (0 && last_snapshot >= BTRFS_I(inode)->generation)
 			/* the inode is shared */
 			new = record_old_file_extents(inode, ordered_extent);
 
-- 
1.8.3.1

Re: [PATCH] Btrfs: disable snapshot aware defrag for now

[David Sterba]

On Wed, Jan 29, 2014 at 04:05:30PM -0500, Josef Bacik wrote:
> It's just broken and it's taking a lot of effort to fix it, so for now just
> disable it so people can defrag in peace.  Thanks,
> 
> Cc: stable@vger.kernel.org
> Signed-off-by: Josef Bacik <jbacik@fb.com>
> ---
>  fs/btrfs/inode.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
> index 3b65987..8c0bc31 100644
> --- a/fs/btrfs/inode.c
> +++ b/fs/btrfs/inode.c
> @@ -2628,7 +2628,7 @@ static int btrfs_finish_ordered_io(struct btrfs_ordered_extent *ordered_extent)
>  			EXTENT_DEFRAG, 1, cached_state);
>  	if (ret) {
>  		u64 last_snapshot = btrfs_root_last_snapshot(&root->root_item);
> -		if (last_snapshot >= BTRFS_I(inode)->generation)
> +		if (0 && last_snapshot >= BTRFS_I(inode)->generation)

That's not very flexible, how are we supposed to test that in the
meantime? Editing sources is not the peferred way.

I was thinking about adding a config option that would cover any
experimental/broken features, this one be the first, as we currently
have no other way to disable it. I'd rather avoid adding a temporary
mount option.

Re: [PATCH] Btrfs: disable snapshot aware defrag for now

[Josef Bacik]

On 02/03/2014 09:48 AM, David Sterba wrote:
> On Wed, Jan 29, 2014 at 04:05:30PM -0500, Josef Bacik wrote:
>> It's just broken and it's taking a lot of effort to fix it, so for now just
>> disable it so people can defrag in peace.  Thanks,
>>
>> Cc: stable@vger.kernel.org
>> Signed-off-by: Josef Bacik <jbacik@fb.com>
>> ---
>>   fs/btrfs/inode.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
>> index 3b65987..8c0bc31 100644
>> --- a/fs/btrfs/inode.c
>> +++ b/fs/btrfs/inode.c
>> @@ -2628,7 +2628,7 @@ static int btrfs_finish_ordered_io(struct btrfs_ordered_extent *ordered_extent)
>>   			EXTENT_DEFRAG, 1, cached_state);
>>   	if (ret) {
>>   		u64 last_snapshot = btrfs_root_last_snapshot(&root->root_item);
>> -		if (last_snapshot >= BTRFS_I(inode)->generation)
>> +		if (0 && last_snapshot >= BTRFS_I(inode)->generation)
> That's not very flexible, how are we supposed to test that in the
> meantime? Editing sources is not the peferred way.

Well since I'm the only one currently working on fixing it I'm not 
worried about it.  If anybody else wants to fix it they can easily 
change it themselves.  It is so totally broken that I don't want it 
being turned on by anybody who can't edit this and change it 
themselves.  Thanks,

Josef

Re: [PATCH] Btrfs: disable snapshot aware defrag for now

[Roger Binns]

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On 03/02/14 09:27, Josef Bacik wrote:
> It is so totally broken that I don't want it being turned on by anybody
> who can't edit this and change it themselves.

The symptoms I saw are huge amounts of kernel memory consumption, possibly
till exhaustion of swap.  Are there other ways in which is it broken (eg
corruption)?

Also is this patch making its way to the various stables?

Roger

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Re: [PATCH] Btrfs: disable snapshot aware defrag for now

[Josef Bacik]

On 02/03/2014 10:19 PM, Roger Binns wrote:
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
>
> On 03/02/14 09:27, Josef Bacik wrote:
>> It is so totally broken that I don't want it being turned on by anybody
>> who can't edit this and change it themselves.
> The symptoms I saw are huge amounts of kernel memory consumption, possibly
> till exhaustion of swap.  Are there other ways in which is it broken (eg
> corruption)?
>
> Also is this patch making its way to the various stables?
No corruption, and frankly if you had just small files and a small 
number of snapshots it worked just fine, but otherwise it would use all 
of your ram.  I cc'ed stable@ so it should make it back to all the 
stables.  Thanks,

Josef