[PATCH] btrfs: Remove WARN_ON for unaligned device created before v4.13 and adds more user friendly output

[PATCH] btrfs: Remove WARN_ON for unaligned device created before v4.13 and adds more user friendly output

[Qu Wenruo]

Commit 7dfb8be11b5d ("btrfs: Round down values which are written for
total_bytes_size") is fixing the unaligned device size caused by
adding/shrinking device.

It added a new WARN_ON() when device size is unaligned.
This is fine for new device added to btrfs using v4.13 kernel, but not
existing device whose total_bytes is already unaligned.

And the WARN_ON() will get triggered every time a block group get
created/removed on the unaligned device.

This patch will remove the WARN_ON(), and warn user more gently what's
happening and how to fix it.

Reported-by: Rich Rauenzahn <rich@shroop.net>
Fixes: 7dfb8be11b5d ("btrfs: Round down values which are written for
total_bytes_size")
Signed-off-by: Qu Wenruo <quwenruo.btrfs@gmx.com>
---
 fs/btrfs/ctree.h   |  1 -
 fs/btrfs/volumes.c | 16 ++++++++++++----
 2 files changed, 12 insertions(+), 5 deletions(-)

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 5a8933da39a7..4de9269e435a 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -1562,7 +1562,6 @@ static inline void btrfs_set_device_total_bytes(struct extent_buffer *eb,
 {
 	BUILD_BUG_ON(sizeof(u64) !=
 		     sizeof(((struct btrfs_dev_item *)0))->total_bytes);
-	WARN_ON(!IS_ALIGNED(val, eb->fs_info->sectorsize));
 	btrfs_set_64(eb, s, offsetof(struct btrfs_dev_item, total_bytes), val);
 }
 
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 0e8f16c305df..afae25df6a8c 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -6472,15 +6472,23 @@ static int read_one_chunk(struct btrfs_fs_info *fs_info, struct btrfs_key *key,
 	return 0;
 }
 
-static void fill_device_from_item(struct extent_buffer *leaf,
-				 struct btrfs_dev_item *dev_item,
-				 struct btrfs_device *device)
+static void fill_device_from_item(struct btrfs_fs_info *fs_info,
+				  struct extent_buffer *leaf,
+				  struct btrfs_dev_item *dev_item,
+				  struct btrfs_device *device)
 {
 	unsigned long ptr;
 
 	device->devid = btrfs_device_id(leaf, dev_item);
 	device->disk_total_bytes = btrfs_device_total_bytes(leaf, dev_item);
 	device->total_bytes = device->disk_total_bytes;
+	if (!IS_ALIGNED(device->total_bytes, fs_info->sectorsize)) {
+		btrfs_warn(fs_info,
+			   "devid %llu has unaligned total bytes %llu",
+			   device->devid, device->disk_total_bytes);
+		btrfs_warn(fs_info,
+			   "please shrink the device a little and resize back to fix it");
+	}
 	device->commit_total_bytes = device->disk_total_bytes;
 	device->bytes_used = btrfs_device_bytes_used(leaf, dev_item);
 	device->commit_bytes_used = device->bytes_used;
@@ -6625,7 +6633,7 @@ static int read_one_dev(struct btrfs_fs_info *fs_info,
 			return -EINVAL;
 	}
 
-	fill_device_from_item(leaf, dev_item, device);
+	fill_device_from_item(fs_info, leaf, dev_item, device);
 	device->in_fs_metadata = 1;
 	if (device->writeable && !device->is_tgtdev_for_dev_replace) {
 		device->fs_devices->total_rw_bytes += device->total_bytes;
-- 
2.14.1

Re: [PATCH] btrfs: Remove WARN_ON for unaligned device created before v4.13 and adds more user friendly output

[Satoru Takeuchi]

At Wed, 20 Sep 2017 15:18:43 +0900,
Qu Wenruo wrote:
> 
> Commit 7dfb8be11b5d ("btrfs: Round down values which are written for
> total_bytes_size") is fixing the unaligned device size caused by
> adding/shrinking device.
> 
> It added a new WARN_ON() when device size is unaligned.
> This is fine for new device added to btrfs using v4.13 kernel, but not
> existing device whose total_bytes is already unaligned.
> 
> And the WARN_ON() will get triggered every time a block group get
> created/removed on the unaligned device.
> 
> This patch will remove the WARN_ON(), and warn user more gently what's
> happening and how to fix it.
> 
> Reported-by: Rich Rauenzahn <rich@shroop.net>
> Fixes: 7dfb8be11b5d ("btrfs: Round down values which are written for
> total_bytes_size")
> Signed-off-by: Qu Wenruo <quwenruo.btrfs@gmx.com>
> ---
>  fs/btrfs/ctree.h   |  1 -
>  fs/btrfs/volumes.c | 16 ++++++++++++----
>  2 files changed, 12 insertions(+), 5 deletions(-)
> 
> diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
> index 5a8933da39a7..4de9269e435a 100644
> --- a/fs/btrfs/ctree.h
> +++ b/fs/btrfs/ctree.h
> @@ -1562,7 +1562,6 @@ static inline void btrfs_set_device_total_bytes(struct extent_buffer *eb,
>  {
>  	BUILD_BUG_ON(sizeof(u64) !=
>  		     sizeof(((struct btrfs_dev_item *)0))->total_bytes);
> -	WARN_ON(!IS_ALIGNED(val, eb->fs_info->sectorsize));
>  	btrfs_set_64(eb, s, offsetof(struct btrfs_dev_item, total_bytes), val);
>  }
>  
> diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
> index 0e8f16c305df..afae25df6a8c 100644
> --- a/fs/btrfs/volumes.c
> +++ b/fs/btrfs/volumes.c
> @@ -6472,15 +6472,23 @@ static int read_one_chunk(struct btrfs_fs_info *fs_info, struct btrfs_key *key,
>  	return 0;
>  }
>  
> -static void fill_device_from_item(struct extent_buffer *leaf,
> -				 struct btrfs_dev_item *dev_item,
> -				 struct btrfs_device *device)
> +static void fill_device_from_item(struct btrfs_fs_info *fs_info,
> +				  struct extent_buffer *leaf,
> +				  struct btrfs_dev_item *dev_item,
> +				  struct btrfs_device *device)
>  {
>  	unsigned long ptr;
>  
>  	device->devid = btrfs_device_id(leaf, dev_item);
>  	device->disk_total_bytes = btrfs_device_total_bytes(leaf, dev_item);
>  	device->total_bytes = device->disk_total_bytes;
> +	if (!IS_ALIGNED(device->total_bytes, fs_info->sectorsize)) {
> +		btrfs_warn(fs_info,
> +			   "devid %llu has unaligned total bytes %llu",
> +			   device->devid, device->disk_total_bytes);
> +		btrfs_warn(fs_info,
> +			   "please shrink the device a little and resize back to fix it");
> +	}

How about telling uses to know device->total_bytes should be alligned
to fs_info->sectorsize here?

Thanks,
Satoru

>  	device->commit_total_bytes = device->disk_total_bytes;
>  	device->bytes_used = btrfs_device_bytes_used(leaf, dev_item);
>  	device->commit_bytes_used = device->bytes_used;
> @@ -6625,7 +6633,7 @@ static int read_one_dev(struct btrfs_fs_info *fs_info,
>  			return -EINVAL;
>  	}
>  
> -	fill_device_from_item(leaf, dev_item, device);
> +	fill_device_from_item(fs_info, leaf, dev_item, device);
>  	device->in_fs_metadata = 1;
>  	if (device->writeable && !device->is_tgtdev_for_dev_replace) {
>  		device->fs_devices->total_rw_bytes += device->total_bytes;
> -- 
> 2.14.1
> 
> --
> To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html

Re: [PATCH] btrfs: Remove WARN_ON for unaligned device created before v4.13 and adds more user friendly output

[Satoru Takeuchi]

At Sat, 23 Sep 2017 10:19:26 +0900,
Satoru Takeuchi wrote:
> 
> At Wed, 20 Sep 2017 15:18:43 +0900,
> Qu Wenruo wrote:
> > 
> > Commit 7dfb8be11b5d ("btrfs: Round down values which are written for
> > total_bytes_size") is fixing the unaligned device size caused by
> > adding/shrinking device.
> > 
> > It added a new WARN_ON() when device size is unaligned.
> > This is fine for new device added to btrfs using v4.13 kernel, but not
> > existing device whose total_bytes is already unaligned.
> > 
> > And the WARN_ON() will get triggered every time a block group get
> > created/removed on the unaligned device.
> > 
> > This patch will remove the WARN_ON(), and warn user more gently what's
> > happening and how to fix it.
> > 
> > Reported-by: Rich Rauenzahn <rich@shroop.net>
> > Fixes: 7dfb8be11b5d ("btrfs: Round down values which are written for
> > total_bytes_size")
> > Signed-off-by: Qu Wenruo <quwenruo.btrfs@gmx.com>
> > ---
> >  fs/btrfs/ctree.h   |  1 -
> >  fs/btrfs/volumes.c | 16 ++++++++++++----
> >  2 files changed, 12 insertions(+), 5 deletions(-)
> > 
> > diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
> > index 5a8933da39a7..4de9269e435a 100644
> > --- a/fs/btrfs/ctree.h
> > +++ b/fs/btrfs/ctree.h
> > @@ -1562,7 +1562,6 @@ static inline void btrfs_set_device_total_bytes(struct extent_buffer *eb,
> >  {
> >  	BUILD_BUG_ON(sizeof(u64) !=
> >  		     sizeof(((struct btrfs_dev_item *)0))->total_bytes);
> > -	WARN_ON(!IS_ALIGNED(val, eb->fs_info->sectorsize));
> >  	btrfs_set_64(eb, s, offsetof(struct btrfs_dev_item, total_bytes), val);
> >  }
> >  
> > diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
> > index 0e8f16c305df..afae25df6a8c 100644
> > --- a/fs/btrfs/volumes.c
> > +++ b/fs/btrfs/volumes.c
> > @@ -6472,15 +6472,23 @@ static int read_one_chunk(struct btrfs_fs_info *fs_info, struct btrfs_key *key,
> >  	return 0;
> >  }
> >  
> > -static void fill_device_from_item(struct extent_buffer *leaf,
> > -				 struct btrfs_dev_item *dev_item,
> > -				 struct btrfs_device *device)
> > +static void fill_device_from_item(struct btrfs_fs_info *fs_info,
> > +				  struct extent_buffer *leaf,
> > +				  struct btrfs_dev_item *dev_item,
> > +				  struct btrfs_device *device)
> >  {
> >  	unsigned long ptr;
> >  
> >  	device->devid = btrfs_device_id(leaf, dev_item);
> >  	device->disk_total_bytes = btrfs_device_total_bytes(leaf, dev_item);
> >  	device->total_bytes = device->disk_total_bytes;
> > +	if (!IS_ALIGNED(device->total_bytes, fs_info->sectorsize)) {
> > +		btrfs_warn(fs_info,
> > +			   "devid %llu has unaligned total bytes %llu",
> > +			   device->devid, device->disk_total_bytes);
> > +		btrfs_warn(fs_info,
> > +			   "please shrink the device a little and resize back to fix it");
> > +	}
> 
> How about telling uses to know device->total_bytes should be alligned
> to fs_info->sectorsize here?
> 
> Thanks,

I should make my comment clearer, sorry.

===
+	if (!IS_ALIGNED(device->total_bytes, fs_info->sectorsize)) {
+		btrfs_warn(fs_info,
+			   "devid %llu: total bytes %llu should be aligned to %u bytes",
+			   device->devid, device->disk_total_bytes, fs_info->sectorsize);
+		btrfs_warn(fs_info,
+			   "please shrink the device a little and resize back to fix it");
+	}
===

Thanks,
Satoru

> Satoru
> 
> >  	device->commit_total_bytes = device->disk_total_bytes;
> >  	device->bytes_used = btrfs_device_bytes_used(leaf, dev_item);
> >  	device->commit_bytes_used = device->bytes_used;
> > @@ -6625,7 +6633,7 @@ static int read_one_dev(struct btrfs_fs_info *fs_info,
> >  			return -EINVAL;
> >  	}
> >  
> > -	fill_device_from_item(leaf, dev_item, device);
> > +	fill_device_from_item(fs_info, leaf, dev_item, device);
> >  	device->in_fs_metadata = 1;
> >  	if (device->writeable && !device->is_tgtdev_for_dev_replace) {
> >  		device->fs_devices->total_rw_bytes += device->total_bytes;
> > -- 
> > 2.14.1
> > 
> > --
> > To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
> > the body of a message to majordomo@vger.kernel.org
> > More majordomo info at  http://vger.kernel.org/majordomo-info.html

Re: [PATCH] btrfs: Remove WARN_ON for unaligned device created before v4.13 and adds more user friendly output

[Qu Wenruo]

On 2017年09月23日 09:27, Satoru Takeuchi wrote:
> At Sat, 23 Sep 2017 10:19:26 +0900,
> Satoru Takeuchi wrote:
>>
>> At Wed, 20 Sep 2017 15:18:43 +0900,
>> Qu Wenruo wrote:
>>>
>>> Commit 7dfb8be11b5d ("btrfs: Round down values which are written for
>>> total_bytes_size") is fixing the unaligned device size caused by
>>> adding/shrinking device.
>>>
>>> It added a new WARN_ON() when device size is unaligned.
>>> This is fine for new device added to btrfs using v4.13 kernel, but not
>>> existing device whose total_bytes is already unaligned.
>>>
>>> And the WARN_ON() will get triggered every time a block group get
>>> created/removed on the unaligned device.
>>>
>>> This patch will remove the WARN_ON(), and warn user more gently what's
>>> happening and how to fix it.
>>>
>>> Reported-by: Rich Rauenzahn <rich@shroop.net>
>>> Fixes: 7dfb8be11b5d ("btrfs: Round down values which are written for
>>> total_bytes_size")
>>> Signed-off-by: Qu Wenruo <quwenruo.btrfs@gmx.com>
>>> ---
>>>   fs/btrfs/ctree.h   |  1 -
>>>   fs/btrfs/volumes.c | 16 ++++++++++++----
>>>   2 files changed, 12 insertions(+), 5 deletions(-)
>>>
>>> diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
>>> index 5a8933da39a7..4de9269e435a 100644
>>> --- a/fs/btrfs/ctree.h
>>> +++ b/fs/btrfs/ctree.h
>>> @@ -1562,7 +1562,6 @@ static inline void btrfs_set_device_total_bytes(struct extent_buffer *eb,
>>>   {
>>>   	BUILD_BUG_ON(sizeof(u64) !=
>>>   		     sizeof(((struct btrfs_dev_item *)0))->total_bytes);
>>> -	WARN_ON(!IS_ALIGNED(val, eb->fs_info->sectorsize));
>>>   	btrfs_set_64(eb, s, offsetof(struct btrfs_dev_item, total_bytes), val);
>>>   }
>>>   
>>> diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
>>> index 0e8f16c305df..afae25df6a8c 100644
>>> --- a/fs/btrfs/volumes.c
>>> +++ b/fs/btrfs/volumes.c
>>> @@ -6472,15 +6472,23 @@ static int read_one_chunk(struct btrfs_fs_info *fs_info, struct btrfs_key *key,
>>>   	return 0;
>>>   }
>>>   
>>> -static void fill_device_from_item(struct extent_buffer *leaf,
>>> -				 struct btrfs_dev_item *dev_item,
>>> -				 struct btrfs_device *device)
>>> +static void fill_device_from_item(struct btrfs_fs_info *fs_info,
>>> +				  struct extent_buffer *leaf,
>>> +				  struct btrfs_dev_item *dev_item,
>>> +				  struct btrfs_device *device)
>>>   {
>>>   	unsigned long ptr;
>>>   
>>>   	device->devid = btrfs_device_id(leaf, dev_item);
>>>   	device->disk_total_bytes = btrfs_device_total_bytes(leaf, dev_item);
>>>   	device->total_bytes = device->disk_total_bytes;
>>> +	if (!IS_ALIGNED(device->total_bytes, fs_info->sectorsize)) {
>>> +		btrfs_warn(fs_info,
>>> +			   "devid %llu has unaligned total bytes %llu",
>>> +			   device->devid, device->disk_total_bytes);
>>> +		btrfs_warn(fs_info,
>>> +			   "please shrink the device a little and resize back to fix it");
>>> +	}
>>
>> How about telling uses to know device->total_bytes should be alligned
>> to fs_info->sectorsize here?
>>
>> Thanks,
> 
> I should make my comment clearer, sorry.
> 
> ===
> +	if (!IS_ALIGNED(device->total_bytes, fs_info->sectorsize)) {
> +		btrfs_warn(fs_info,
> +			   "devid %llu: total bytes %llu should be aligned to %u bytes",
> +			   device->devid, device->disk_total_bytes, fs_info->sectorsize);
> +		btrfs_warn(fs_info,
> +			   "please shrink the device a little and resize back to fix it");
> +	}
> ===

That's better.

But I'm also considering modifying the total_bytes directly here.
So that any time DEV_ITEM and super block get updated, new aligned value 
will be written back to disk, and since the value is aligned in memory, 
it won't cause WARN_ON() any longer.

I'll test and check the code for confirmation before updating the patch.

Thanks,
Qu

> 
> Thanks,
> Satoru
> 
>> Satoru
>>
>>>   	device->commit_total_bytes = device->disk_total_bytes;
>>>   	device->bytes_used = btrfs_device_bytes_used(leaf, dev_item);
>>>   	device->commit_bytes_used = device->bytes_used;
>>> @@ -6625,7 +6633,7 @@ static int read_one_dev(struct btrfs_fs_info *fs_info,
>>>   			return -EINVAL;
>>>   	}
>>>   
>>> -	fill_device_from_item(leaf, dev_item, device);
>>> +	fill_device_from_item(fs_info, leaf, dev_item, device);
>>>   	device->in_fs_metadata = 1;
>>>   	if (device->writeable && !device->is_tgtdev_for_dev_replace) {
>>>   		device->fs_devices->total_rw_bytes += device->total_bytes;
>>> -- 
>>> 2.14.1
>>>
>>> --
>>> To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
>>> the body of a message to majordomo@vger.kernel.org
>>> More majordomo info at  http://vger.kernel.org/majordomo-info.html

Re: [PATCH] btrfs: Remove WARN_ON for unaligned device created before v4.13 and adds more user friendly output

[David Sterba]

On Sat, Sep 23, 2017 at 03:22:36PM +0800, Qu Wenruo wrote:
> >>> --- a/fs/btrfs/volumes.c
> >>> +++ b/fs/btrfs/volumes.c
> >>> @@ -6472,15 +6472,23 @@ static int read_one_chunk(struct btrfs_fs_info *fs_info, struct btrfs_key *key,
> >>>   	return 0;
> >>>   }
> >>>   
> >>> -static void fill_device_from_item(struct extent_buffer *leaf,
> >>> -				 struct btrfs_dev_item *dev_item,
> >>> -				 struct btrfs_device *device)
> >>> +static void fill_device_from_item(struct btrfs_fs_info *fs_info,
> >>> +				  struct extent_buffer *leaf,
> >>> +				  struct btrfs_dev_item *dev_item,
> >>> +				  struct btrfs_device *device)
> >>>   {
> >>>   	unsigned long ptr;
> >>>   
> >>>   	device->devid = btrfs_device_id(leaf, dev_item);
> >>>   	device->disk_total_bytes = btrfs_device_total_bytes(leaf, dev_item);
> >>>   	device->total_bytes = device->disk_total_bytes;
> >>> +	if (!IS_ALIGNED(device->total_bytes, fs_info->sectorsize)) {
> >>> +		btrfs_warn(fs_info,
> >>> +			   "devid %llu has unaligned total bytes %llu",
> >>> +			   device->devid, device->disk_total_bytes);
> >>> +		btrfs_warn(fs_info,
> >>> +			   "please shrink the device a little and resize back to fix it");
> >>> +	}
> >>
> >> How about telling uses to know device->total_bytes should be alligned
> >> to fs_info->sectorsize here?
> >>
> >> Thanks,
> > 
> > I should make my comment clearer, sorry.
> > 
> > ===
> > +	if (!IS_ALIGNED(device->total_bytes, fs_info->sectorsize)) {
> > +		btrfs_warn(fs_info,
> > +			   "devid %llu: total bytes %llu should be aligned to %u bytes",
> > +			   device->devid, device->disk_total_bytes, fs_info->sectorsize);
> > +		btrfs_warn(fs_info,
> > +			   "please shrink the device a little and resize back to fix it");
> > +	}
> > ===
> 
> That's better.
> 
> But I'm also considering modifying the total_bytes directly here.

Yeah, I think it would be better to fix here, without a warning even.
The rounding error is below 4k and nodesize, we would never use this
space for block groups so no accidental data loss.

> So that any time DEV_ITEM and super block get updated, new aligned value 
> will be written back to disk, and since the value is aligned in memory, 
> it won't cause WARN_ON() any longer.
> 
> I'll test and check the code for confirmation before updating the patch.