[PATCH] Btrfs: fix enospc in punch hole

[PATCH] Btrfs: fix enospc in punch hole

[robbieko]

From: Robbie Ko <robbieko@synology.com>

when extent-tree level > BTRFS_MAX_LEVEL / 2,
__btrfs_drop_extents -> btrfs_duplicate_item ->
setup_leaf_for_split -> split_leaf
maybe enospc, because min_size is too small,
need use btrfs_calc_trans_metadata_size.

Signed-off-by: Robbie Ko <robbieko@synology.com>
---
 fs/btrfs/file.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index fea31a4..809ca85 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -2322,7 +2322,7 @@ static int btrfs_punch_hole(struct inode *inode, loff_t offset, loff_t len)
 	u64 tail_len;
 	u64 orig_start = offset;
 	u64 cur_offset;
-	u64 min_size = btrfs_calc_trunc_metadata_size(root, 1);
+	u64 min_size = btrfs_calc_trans_metadata_size(root, 1);
 	u64 drop_end;
 	int ret = 0;
 	int err = 0;
@@ -2469,7 +2469,7 @@ static int btrfs_punch_hole(struct inode *inode, loff_t offset, loff_t len)
 		ret = -ENOMEM;
 		goto out_free;
 	}
-	rsv->size = btrfs_calc_trunc_metadata_size(root, 1);
+	rsv->size = btrfs_calc_trans_metadata_size(root, 1);
 	rsv->failfast = 1;
 
 	/*
-- 
1.9.1

Re: [PATCH] Btrfs: fix enospc in punch hole

[Filipe Manana]

On Fri, Oct 7, 2016 at 7:09 AM, robbieko <robbieko@synology.com> wrote:
> From: Robbie Ko <robbieko@synology.com>
>
> when extent-tree level > BTRFS_MAX_LEVEL / 2,
> __btrfs_drop_extents -> btrfs_duplicate_item ->
> setup_leaf_for_split -> split_leaf
> maybe enospc, because min_size is too small,
> need use btrfs_calc_trans_metadata_size.

This change log is terrible.
You should describe the problem and fix. That is, that hole punching
can result in adding new leafs (and as a consequence new nodes) to the
tree because when we find file extent items that span beyond the hole
range we may end up not deleting them (just adjusting them) and add
new file extent items representing holes.

And I don't see why this is exclusive for the case where the height of
the extent tree is greater than 4 (BTRFS_MAX_LEVEL / 2).

The code changes themselves look good to me.

thanks

>
> Signed-off-by: Robbie Ko <robbieko@synology.com>
> ---
>  fs/btrfs/file.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
> index fea31a4..809ca85 100644
> --- a/fs/btrfs/file.c
> +++ b/fs/btrfs/file.c
> @@ -2322,7 +2322,7 @@ static int btrfs_punch_hole(struct inode *inode, loff_t offset, loff_t len)
>         u64 tail_len;
>         u64 orig_start = offset;
>         u64 cur_offset;
> -       u64 min_size = btrfs_calc_trunc_metadata_size(root, 1);
> +       u64 min_size = btrfs_calc_trans_metadata_size(root, 1);
>         u64 drop_end;
>         int ret = 0;
>         int err = 0;
> @@ -2469,7 +2469,7 @@ static int btrfs_punch_hole(struct inode *inode, loff_t offset, loff_t len)
>                 ret = -ENOMEM;
>                 goto out_free;
>         }
> -       rsv->size = btrfs_calc_trunc_metadata_size(root, 1);
> +       rsv->size = btrfs_calc_trans_metadata_size(root, 1);
>         rsv->failfast = 1;
>
>         /*
> --
> 1.9.1
>
> --
> 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



-- 
Filipe David Manana,

"People will forget what you said,
 people will forget what you did,
 but people will never forget how you made them feel."

Re: [PATCH] Btrfs: fix enospc in punch hole

[robbieko]

Hi Filipe:

because btrfs_calc_trunc_metadata_size is reserved leafsize + nodesize * 
(8 - 1)
assume leafsize is the same as nodesize, we total reserved 8 nodesize
when split leaf, we need 2 path, if extent_tree level small than 4, it's 
OK
because worst case is (leafsize + nodesize * 3) *2, is 8 nodesize.
but if extent_tree is greater level 4, worst case is need (leafsize + 
nodesize * 7) * 2,
is bigger than resvered size, so we should use 
btrfs_calc_trans_metadata_size,
is taken into account split leaf case.

Thanks.
robbieko

Filipe Manana 於 2016-10-07 18:18 寫到:
> On Fri, Oct 7, 2016 at 7:09 AM, robbieko <robbieko@synology.com> wrote:
>> From: Robbie Ko <robbieko@synology.com>
>> 
>> when extent-tree level > BTRFS_MAX_LEVEL / 2,
>> __btrfs_drop_extents -> btrfs_duplicate_item ->
>> setup_leaf_for_split -> split_leaf
>> maybe enospc, because min_size is too small,
>> need use btrfs_calc_trans_metadata_size.
> 
> This change log is terrible.
> You should describe the problem and fix. That is, that hole punching
> can result in adding new leafs (and as a consequence new nodes) to the
> tree because when we find file extent items that span beyond the hole
> range we may end up not deleting them (just adjusting them) and add
> new file extent items representing holes.
> 
> And I don't see why this is exclusive for the case where the height of
> the extent tree is greater than 4 (BTRFS_MAX_LEVEL / 2).
> 
> The code changes themselves look good to me.
> 
> thanks
> 
>> 
>> Signed-off-by: Robbie Ko <robbieko@synology.com>
>> ---
>>  fs/btrfs/file.c | 4 ++--
>>  1 file changed, 2 insertions(+), 2 deletions(-)
>> 
>> diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
>> index fea31a4..809ca85 100644
>> --- a/fs/btrfs/file.c
>> +++ b/fs/btrfs/file.c
>> @@ -2322,7 +2322,7 @@ static int btrfs_punch_hole(struct inode *inode, 
>> loff_t offset, loff_t len)
>>         u64 tail_len;
>>         u64 orig_start = offset;
>>         u64 cur_offset;
>> -       u64 min_size = btrfs_calc_trunc_metadata_size(root, 1);
>> +       u64 min_size = btrfs_calc_trans_metadata_size(root, 1);
>>         u64 drop_end;
>>         int ret = 0;
>>         int err = 0;
>> @@ -2469,7 +2469,7 @@ static int btrfs_punch_hole(struct inode *inode, 
>> loff_t offset, loff_t len)
>>                 ret = -ENOMEM;
>>                 goto out_free;
>>         }
>> -       rsv->size = btrfs_calc_trunc_metadata_size(root, 1);
>> +       rsv->size = btrfs_calc_trans_metadata_size(root, 1);
>>         rsv->failfast = 1;
>> 
>>         /*
>> --
>> 1.9.1
>> 
>> --
>> 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: fix enospc in punch hole

[Filipe Manana]

On Tue, Oct 11, 2016 at 9:58 AM, robbieko <robbieko@synology.com> wrote:
> Hi Filipe:
>
> because btrfs_calc_trunc_metadata_size is reserved leafsize + nodesize * (8
> - 1)
> assume leafsize is the same as nodesize

The leaf size is always the same as the node size. There are no exceptions.

> , we total reserved 8 nodesize
> when split leaf, we need 2 path

2 paths?? what do you mean?

> , if extent_tree level small than 4, it's OK
> because worst case is (leafsize + nodesize * 3) *2, is 8 nodesize.
> but if extent_tree is greater level 4, worst case is need (leafsize +
> nodesize * 7) * 2,
> is bigger than resvered size, so we should use
> btrfs_calc_trans_metadata_size,
> is taken into account split leaf case.

I think I can make some sense of what you're saying, but you forgot to
mention that after splitting a leaf (therefore creating a new one), a
new node might be added to each level of the tree (since there's a new
key and every parent node was full).

Having detailed and well written change logs is important...

Thanks


>
> Thanks.
> robbieko
>
> Filipe Manana 於 2016-10-07 18:18 寫到:
>
>> On Fri, Oct 7, 2016 at 7:09 AM, robbieko <robbieko@synology.com> wrote:
>>>
>>> From: Robbie Ko <robbieko@synology.com>
>>>
>>> when extent-tree level > BTRFS_MAX_LEVEL / 2,
>>> __btrfs_drop_extents -> btrfs_duplicate_item ->
>>> setup_leaf_for_split -> split_leaf
>>> maybe enospc, because min_size is too small,
>>> need use btrfs_calc_trans_metadata_size.
>>
>>
>> This change log is terrible.
>> You should describe the problem and fix. That is, that hole punching
>> can result in adding new leafs (and as a consequence new nodes) to the
>> tree because when we find file extent items that span beyond the hole
>> range we may end up not deleting them (just adjusting them) and add
>> new file extent items representing holes.
>>
>> And I don't see why this is exclusive for the case where the height of
>> the extent tree is greater than 4 (BTRFS_MAX_LEVEL / 2).
>>
>> The code changes themselves look good to me.
>>
>> thanks
>>
>>>
>>> Signed-off-by: Robbie Ko <robbieko@synology.com>
>>> ---
>>>  fs/btrfs/file.c | 4 ++--
>>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
>>> index fea31a4..809ca85 100644
>>> --- a/fs/btrfs/file.c
>>> +++ b/fs/btrfs/file.c
>>> @@ -2322,7 +2322,7 @@ static int btrfs_punch_hole(struct inode *inode,
>>> loff_t offset, loff_t len)
>>>         u64 tail_len;
>>>         u64 orig_start = offset;
>>>         u64 cur_offset;
>>> -       u64 min_size = btrfs_calc_trunc_metadata_size(root, 1);
>>> +       u64 min_size = btrfs_calc_trans_metadata_size(root, 1);
>>>         u64 drop_end;
>>>         int ret = 0;
>>>         int err = 0;
>>> @@ -2469,7 +2469,7 @@ static int btrfs_punch_hole(struct inode *inode,
>>> loff_t offset, loff_t len)
>>>                 ret = -ENOMEM;
>>>                 goto out_free;
>>>         }
>>> -       rsv->size = btrfs_calc_trunc_metadata_size(root, 1);
>>> +       rsv->size = btrfs_calc_trans_metadata_size(root, 1);
>>>         rsv->failfast = 1;
>>>
>>>         /*
>>> --
>>> 1.9.1
>>>
>>> --
>>> 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
>
>



-- 
Filipe David Manana,

"People will forget what you said,
 people will forget what you did,
 but people will never forget how you made them feel."