[RFC PATCH] btrfs: flush_space: treat return value of do_chunk_alloc properly

[RFC PATCH] btrfs: flush_space: treat return value of do_chunk_alloc properly

[Alex Lyakas]

do_chunk_alloc returns 1 when it succeeds to allocate a new chunk.
But flush_space will not convert this to 0, and will also return 1.
As a result, reserve_metadata_bytes will think that flush_space failed,
and may potentially return this value "1" to the caller (depends how
reserve_metadata_bytes was called). The caller will also treat this as an error.
For example, btrfs_block_rsv_refill does:

int ret = -ENOSPC;
...
ret = reserve_metadata_bytes(root, block_rsv, num_bytes, flush);
if (!ret) {
        block_rsv_add_bytes(block_rsv, num_bytes, 0);
        return 0;
}

return ret;

So it will return -ENOSPC.

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 4b89680..1ba3f0d 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -4727,7 +4727,7 @@ static int flush_space(struct btrfs_root *root,
                                     btrfs_get_alloc_profile(root, 0),
                                     CHUNK_ALLOC_NO_FORCE);
                btrfs_end_transaction(trans, root);
-               if (ret == -ENOSPC)
+               if (ret > 0 || ret == -ENOSPC)
                        ret = 0;
                break;
        case COMMIT_TRANS:

Re: [RFC PATCH] btrfs: flush_space: treat return value of do_chunk_alloc properly

[Liu Bo]

On Thu, Dec 03, 2015 at 06:51:03PM +0200, Alex Lyakas wrote:
> do_chunk_alloc returns 1 when it succeeds to allocate a new chunk.
> But flush_space will not convert this to 0, and will also return 1.
> As a result, reserve_metadata_bytes will think that flush_space failed,
> and may potentially return this value "1" to the caller (depends how
> reserve_metadata_bytes was called). The caller will also treat this as an error.
> For example, btrfs_block_rsv_refill does:
> 
> int ret = -ENOSPC;
> ...
> ret = reserve_metadata_bytes(root, block_rsv, num_bytes, flush);
> if (!ret) {
>         block_rsv_add_bytes(block_rsv, num_bytes, 0);
>         return 0;
> }
> 
> return ret;
> 
> So it will return -ENOSPC.

It will return 1 instead of -ENOSPC.

The patch looks good, I noticed this before, but I didn't manage to trigger a error for this, did you catch a error like that?

Thanks,

-liubo

> 
> diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
> index 4b89680..1ba3f0d 100644
> --- a/fs/btrfs/extent-tree.c
> +++ b/fs/btrfs/extent-tree.c
> @@ -4727,7 +4727,7 @@ static int flush_space(struct btrfs_root *root,
>                                      btrfs_get_alloc_profile(root, 0),
>                                      CHUNK_ALLOC_NO_FORCE);
>                 btrfs_end_transaction(trans, root);
> -               if (ret == -ENOSPC)
> +               if (ret > 0 || ret == -ENOSPC)
>                         ret = 0;
>                 break;
>         case COMMIT_TRANS:
> --
> 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: [RFC PATCH] btrfs: flush_space: treat return value of do_chunk_alloc properly

[Alex Lyakas]

Hi Liu,
I was studying on how block reservation works, and making some
modifications in reserve_metadata_bytes to understand better what it
does. Then suddenly I saw this problem. I guess it depends on which
value of "flush" parameter is passed to reserve_metadata_bytes.

Alex.


On Thu, Dec 3, 2015 at 8:14 PM, Liu Bo <bo.li.liu@oracle.com> wrote:
> On Thu, Dec 03, 2015 at 06:51:03PM +0200, Alex Lyakas wrote:
>> do_chunk_alloc returns 1 when it succeeds to allocate a new chunk.
>> But flush_space will not convert this to 0, and will also return 1.
>> As a result, reserve_metadata_bytes will think that flush_space failed,
>> and may potentially return this value "1" to the caller (depends how
>> reserve_metadata_bytes was called). The caller will also treat this as an error.
>> For example, btrfs_block_rsv_refill does:
>>
>> int ret = -ENOSPC;
>> ...
>> ret = reserve_metadata_bytes(root, block_rsv, num_bytes, flush);
>> if (!ret) {
>>         block_rsv_add_bytes(block_rsv, num_bytes, 0);
>>         return 0;
>> }
>>
>> return ret;
>>
>> So it will return -ENOSPC.
>
> It will return 1 instead of -ENOSPC.
>
> The patch looks good, I noticed this before, but I didn't manage to trigger a error for this, did you catch a error like that?
>
> Thanks,
>
> -liubo
>
>>
>> diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
>> index 4b89680..1ba3f0d 100644
>> --- a/fs/btrfs/extent-tree.c
>> +++ b/fs/btrfs/extent-tree.c
>> @@ -4727,7 +4727,7 @@ static int flush_space(struct btrfs_root *root,
>>                                      btrfs_get_alloc_profile(root, 0),
>>                                      CHUNK_ALLOC_NO_FORCE);
>>                 btrfs_end_transaction(trans, root);
>> -               if (ret == -ENOSPC)
>> +               if (ret > 0 || ret == -ENOSPC)
>>                         ret = 0;
>>                 break;
>>         case COMMIT_TRANS:
>> --
>> 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: [RFC PATCH] btrfs: flush_space: treat return value of do_chunk_alloc properly

[Alex Lyakas]

do_chunk_alloc returns 1 when it succeeds to allocate a new chunk.
But flush_space will not convert this to 0, and will also return 1.
As a result, reserve_metadata_bytes will think that flush_space failed,
and may potentially return this value "1" to the caller (depends how
reserve_metadata_bytes was called). The caller will also treat this as an error.
For example, btrfs_block_rsv_refill does:

int ret = -ENOSPC;
...
ret = reserve_metadata_bytes(root, block_rsv, num_bytes, flush);
if (!ret) {
        block_rsv_add_bytes(block_rsv, num_bytes, 0);
        return 0;
}

return ret;

So it will return -ENOSPC.

Signed-off-by: Alex Lyakas <alex@zadarastorage.com>
Reviewed-by: Josef Bacik <jbacik@fb.com>

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 4b89680..1ba3f0d 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -4727,7 +4727,7 @@ static int flush_space(struct btrfs_root *root,
                                     btrfs_get_alloc_profile(root, 0),
                                     CHUNK_ALLOC_NO_FORCE);
                btrfs_end_transaction(trans, root);
-               if (ret == -ENOSPC)
+               if (ret > 0 || ret == -ENOSPC)
                        ret = 0;
                break;
        case COMMIT_TRANS:

On Sun, Dec 6, 2015 at 12:19 PM, Alex Lyakas <alex@zadarastorage.com> wrote:
> Hi Liu,
> I was studying on how block reservation works, and making some
> modifications in reserve_metadata_bytes to understand better what it
> does. Then suddenly I saw this problem. I guess it depends on which
> value of "flush" parameter is passed to reserve_metadata_bytes.
>
> Alex.
>
>
> On Thu, Dec 3, 2015 at 8:14 PM, Liu Bo <bo.li.liu@oracle.com> wrote:
>> On Thu, Dec 03, 2015 at 06:51:03PM +0200, Alex Lyakas wrote:
>>> do_chunk_alloc returns 1 when it succeeds to allocate a new chunk.
>>> But flush_space will not convert this to 0, and will also return 1.
>>> As a result, reserve_metadata_bytes will think that flush_space failed,
>>> and may potentially return this value "1" to the caller (depends how
>>> reserve_metadata_bytes was called). The caller will also treat this as an error.
>>> For example, btrfs_block_rsv_refill does:
>>>
>>> int ret = -ENOSPC;
>>> ...
>>> ret = reserve_metadata_bytes(root, block_rsv, num_bytes, flush);
>>> if (!ret) {
>>>         block_rsv_add_bytes(block_rsv, num_bytes, 0);
>>>         return 0;
>>> }
>>>
>>> return ret;
>>>
>>> So it will return -ENOSPC.
>>
>> It will return 1 instead of -ENOSPC.
>>
>> The patch looks good, I noticed this before, but I didn't manage to trigger a error for this, did you catch a error like that?
>>
>> Thanks,
>>
>> -liubo
>>
>>>
>>> diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
>>> index 4b89680..1ba3f0d 100644
>>> --- a/fs/btrfs/extent-tree.c
>>> +++ b/fs/btrfs/extent-tree.c
>>> @@ -4727,7 +4727,7 @@ static int flush_space(struct btrfs_root *root,
>>>                                      btrfs_get_alloc_profile(root, 0),
>>>                                      CHUNK_ALLOC_NO_FORCE);
>>>                 btrfs_end_transaction(trans, root);
>>> -               if (ret == -ENOSPC)
>>> +               if (ret > 0 || ret == -ENOSPC)
>>>                         ret = 0;
>>>                 break;
>>>         case COMMIT_TRANS:
>>> --
>>> 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: [RFC PATCH] btrfs: flush_space: treat return value of do_chunk_alloc properly

[Liu Bo]

On Sun, Dec 06, 2015 at 12:32:31PM +0200, Alex Lyakas wrote:
> do_chunk_alloc returns 1 when it succeeds to allocate a new chunk.
> But flush_space will not convert this to 0, and will also return 1.
> As a result, reserve_metadata_bytes will think that flush_space failed,
> and may potentially return this value "1" to the caller (depends how
> reserve_metadata_bytes was called). The caller will also treat this as an error.
> For example, btrfs_block_rsv_refill does:
> 
> int ret = -ENOSPC;
> ...
> ret = reserve_metadata_bytes(root, block_rsv, num_bytes, flush);
> if (!ret) {
>         block_rsv_add_bytes(block_rsv, num_bytes, 0);
>         return 0;
> }
> 
> return ret;
> 
> So it will return -ENOSPC.

Reviewed-by: Liu Bo <bo.li.liu@oracle.com>

Thanks,

-liubo
> 
> Signed-off-by: Alex Lyakas <alex@zadarastorage.com>
> Reviewed-by: Josef Bacik <jbacik@fb.com>
> 
> diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
> index 4b89680..1ba3f0d 100644
> --- a/fs/btrfs/extent-tree.c
> +++ b/fs/btrfs/extent-tree.c
> @@ -4727,7 +4727,7 @@ static int flush_space(struct btrfs_root *root,
>                                      btrfs_get_alloc_profile(root, 0),
>                                      CHUNK_ALLOC_NO_FORCE);
>                 btrfs_end_transaction(trans, root);
> -               if (ret == -ENOSPC)
> +               if (ret > 0 || ret == -ENOSPC)
>                         ret = 0;
>                 break;
>         case COMMIT_TRANS:
> 
> On Sun, Dec 6, 2015 at 12:19 PM, Alex Lyakas <alex@zadarastorage.com> wrote:
> > Hi Liu,
> > I was studying on how block reservation works, and making some
> > modifications in reserve_metadata_bytes to understand better what it
> > does. Then suddenly I saw this problem. I guess it depends on which
> > value of "flush" parameter is passed to reserve_metadata_bytes.
> >
> > Alex.
> >
> >
> > On Thu, Dec 3, 2015 at 8:14 PM, Liu Bo <bo.li.liu@oracle.com> wrote:
> >> On Thu, Dec 03, 2015 at 06:51:03PM +0200, Alex Lyakas wrote:
> >>> do_chunk_alloc returns 1 when it succeeds to allocate a new chunk.
> >>> But flush_space will not convert this to 0, and will also return 1.
> >>> As a result, reserve_metadata_bytes will think that flush_space failed,
> >>> and may potentially return this value "1" to the caller (depends how
> >>> reserve_metadata_bytes was called). The caller will also treat this as an error.
> >>> For example, btrfs_block_rsv_refill does:
> >>>
> >>> int ret = -ENOSPC;
> >>> ...
> >>> ret = reserve_metadata_bytes(root, block_rsv, num_bytes, flush);
> >>> if (!ret) {
> >>>         block_rsv_add_bytes(block_rsv, num_bytes, 0);
> >>>         return 0;
> >>> }
> >>>
> >>> return ret;
> >>>
> >>> So it will return -ENOSPC.
> >>
> >> It will return 1 instead of -ENOSPC.
> >>
> >> The patch looks good, I noticed this before, but I didn't manage to trigger a error for this, did you catch a error like that?
> >>
> >> Thanks,
> >>
> >> -liubo
> >>
> >>>
> >>> diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
> >>> index 4b89680..1ba3f0d 100644
> >>> --- a/fs/btrfs/extent-tree.c
> >>> +++ b/fs/btrfs/extent-tree.c
> >>> @@ -4727,7 +4727,7 @@ static int flush_space(struct btrfs_root *root,
> >>>                                      btrfs_get_alloc_profile(root, 0),
> >>>                                      CHUNK_ALLOC_NO_FORCE);
> >>>                 btrfs_end_transaction(trans, root);
> >>> -               if (ret == -ENOSPC)
> >>> +               if (ret > 0 || ret == -ENOSPC)
> >>>                         ret = 0;
> >>>                 break;
> >>>         case COMMIT_TRANS:
> >>> --
> >>> 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: [RFC PATCH] btrfs: flush_space: treat return value of do_chunk_alloc properly

[Josef Bacik]

On 12/03/2015 11:51 AM, Alex Lyakas wrote:
> do_chunk_alloc returns 1 when it succeeds to allocate a new chunk.
> But flush_space will not convert this to 0, and will also return 1.
> As a result, reserve_metadata_bytes will think that flush_space failed,
> and may potentially return this value "1" to the caller (depends how
> reserve_metadata_bytes was called). The caller will also treat this as an error.
> For example, btrfs_block_rsv_refill does:
>
> int ret = -ENOSPC;
> ...
> ret = reserve_metadata_bytes(root, block_rsv, num_bytes, flush);
> if (!ret) {
>          block_rsv_add_bytes(block_rsv, num_bytes, 0);
>          return 0;
> }
>
> return ret;
>
> So it will return -ENOSPC.

Huh nice catch.  Can you add your signed off by, and you can add my

Reviewed-by: Josef Bacik <jbacik@fb.com>

Thanks,

Josef