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

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Message-ID: <bcce4e5c-d739-4b1c-86bd-d165ec0780be@suse.com>
Date: Thu, 27 Mar 2025 14:53:20 +0800
From: Heming Zhao <heming.zhao@...e.com>
To: Gautham Ananthakrishna <gautham.ananthakrishna@...cle.com>,
 "joseph.qi@...ux.alibaba.com" <joseph.qi@...ux.alibaba.com>
Cc: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
 "ocfs2-devel@...ts.linux.dev" <ocfs2-devel@...ts.linux.dev>,
 Rajesh Sivaramasubramaniom <rajesh.sivaramasubramaniom@...cle.com>,
 Junxiao Bi <junxiao.bi@...cle.com>,
 "akpm@...ux-foundation.org" <akpm@...ux-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@...e.com>
> *Sent:* Thursday, March 27, 2025 11:39 AM
> *To:* Gautham Ananthakrishna <gautham.ananthakrishna@...cle.com>; joseph.qi@...ux.alibaba.com <joseph.qi@...ux.alibaba.com>
> *Cc:* linux-kernel@...r.kernel.org <linux-kernel@...r.kernel.org>; ocfs2-devel@...ts.linux.dev <ocfs2-devel@...ts.linux.dev>; Rajesh Sivaramasubramaniom <rajesh.sivaramasubramaniom@...cle.com>; Junxiao Bi <junxiao.bi@...cle.com>; akpm@...ux-foundation.org <akpm@...ux-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@...cle.com>
>> ---
>>   fs/ocfs2/suballoc.c | 146 ++++++++++++++++++++++++++++----------------
>>   1 file changed, 95 insertions(+), 51 deletions(-)
>>