Re: [PATCH RFC 1/1] ocfs2: fix write IO performance improvement for high fragmentation

[Heming Zhao <heming.zhao@suse.com>]

Thank Gautham for the testing job.

Ping Joseph...
Let's quickly fix this bug.
There are two ways to fix the issue in commit 4eb7b93e0310:
- Aautham: https://lore.kernel.org/ocfs2-devel/bcce4e5c-d739-4b1c-86bd-d165ec0780be@suse.com/T/#t
- Heming: https://lore.kernel.org/ocfs2-devel/faef812f-0adc-4a46-951a-5453927c2819@suse.com/T/#t

In my view, my patch is more better.

- Heming

On 4/1/25 12:32, Gautham Ananthakrishna wrote:
> HI Heming,
> 
> I ran the tests on your patch, and it is working fine. The discontig_runner.sh was failing earlier in "Inodes Block Group Test".
> 
> Thanks,
> Gautham.
> ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
> *From:* Heming Zhao <heming.zhao@suse.com>
> *Sent:* Thursday, March 27, 2025 12:23 PM
> *To:* Gautham Ananthakrishna <gautham.ananthakrishna@oracle.com>; joseph.qi@linux.alibaba.com <joseph.qi@linux.alibaba.com>
> *Cc:* linux-kernel@vger.kernel.org <linux-kernel@vger.kernel.org>; ocfs2-devel@lists.linux.dev <ocfs2-devel@lists.linux.dev>; Rajesh Sivaramasubramaniom <rajesh.sivaramasubramaniom@oracle.com>; Junxiao Bi <junxiao.bi@oracle.com>; akpm@linux-foundation.org <akpm@linux-foundation.org>
> *Subject:* Re: [PATCH RFC 1/1] ocfs2: fix write IO performance improvement for high fragmentation
> On 3/27/25 14:21, Gautham Ananthakrishna wrote:
>> HI Heming,
>> 
>> Sharing the test suite may not be practical (it has shell scripts, python and C binaries). However, I can take a look into your patch and run a quick test.
>> 
>> Thanks,
>> Gautham.
>> 
> 
> Thank you for your quick reply and willingness to help.
> 
> - Heming
> ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
>> *From:* Heming Zhao <heming.zhao@suse.com>
>> *Sent:* Thursday, March 27, 2025 11:39 AM
>> *To:* Gautham Ananthakrishna <gautham.ananthakrishna@oracle.com>; joseph.qi@linux.alibaba.com <joseph.qi@linux.alibaba.com>
>> *Cc:* linux-kernel@vger.kernel.org <linux-kernel@vger.kernel.org>; ocfs2-devel@lists.linux.dev <ocfs2-devel@lists.linux.dev>; Rajesh Sivaramasubramaniom <rajesh.sivaramasubramaniom@oracle.com>; Junxiao Bi <junxiao.bi@oracle.com>; akpm@linux-foundation.org <akpm@linux-foundation.org>
>> *Subject:* Re: [PATCH RFC 1/1] ocfs2: fix write IO performance improvement for high fragmentation
>> Hello Gautham,
>> 
>> Thanks for locating the issue and submitting a patch.
>> Is it possible to share your test case for this bug?
>> 
>> The key of this bug is ocfs2_cluster_group_search() comparing with wrong
>> bits size. I have another fix for this bug and will send it to this mailing
>> list later.
>> 
>> Thanks,
>> Heming
>> 
>> On 3/24/25 13:48, Gautham Ananthakrishna wrote:
>>> The commit 4eb7b93e03101fd3f35e69affe566e4b1e3e3dca caused a regression
>>> in our test suite in discontig extent tests. Upon troubleshooting I found
>>> The following issues.
>>> 
>>> 1. The function ocfs2_cluster_group_search() was called for discontig allocations
>>> as well. But it checks only the contiguous bits 'bg_contig_free_bits'.
>>> It hit the ENOSPC in the following case in one of the tests.
>>> 
>>> ocfs2_mkdir()
>>>   ocfs2_reserve_new_inode()
>>>    ocfs2_reserve_suballoc_bits()
>>>     ocfs2_block_group_alloc()
>>>      ocfs2_block_group_alloc_discontig()
>>>       __ocfs2_claim_clusters()
>>>        ocfs2_claim_suballoc_bits()
>>>         ocfs2_search_chain()
>>>          ocfs2_cluster_group_search()
>>> 
>>> Looked like the commit did not consider discontig searches. To fix this,
>>> I have split ocfs2_cluster_group_search() into *_common(), *_contig() and
>>> *_discontig()
>>> 
>>> 2. That commit enforced ocfs2_cluster_group_search() to search only the
>>> 'bits_wanted' number of bits whereas ocfs2_block_group_find_clear_bits()
>>> fills the best available size and the function ocfs2_cluster_group_search()
>>> itself is supposed to search 'min_bits' at the minimum and need not be
>>> 'bits_wanted' always.
>>> 
>>> Fixed the above issues in this patch.
>>> This patch fixes 4eb7b93e03101fd3f35e69affe566e4b1e3e3dca
>>> 
>>> Signed-off-by: Gautham Ananthakrishna <gautham.ananthakrishna@oracle.com>
>>> ---
>>>   fs/ocfs2/suballoc.c | 146 ++++++++++++++++++++++++++++----------------
>>>   1 file changed, 95 insertions(+), 51 deletions(-)
>>> 
>