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

[Heming Zhao]

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@xxxxxxxx>
> *Sent:* Thursday, March 27, 2025 11:39 AM
> *To:* Gautham Ananthakrishna <gautham.ananthakrishna@xxxxxxxxxx>; joseph.qi@xxxxxxxxxxxxxxxxx <joseph.qi@xxxxxxxxxxxxxxxxx>
> *Cc:* linux-kernel@xxxxxxxxxxxxxxx <linux-kernel@xxxxxxxxxxxxxxx>; ocfs2-devel@xxxxxxxxxxxxxxx <ocfs2-devel@xxxxxxxxxxxxxxx>; Rajesh Sivaramasubramaniom <rajesh.sivaramasubramaniom@xxxxxxxxxx>; Junxiao Bi <junxiao.bi@xxxxxxxxxx>; akpm@xxxxxxxxxxxxxxxxxxxx <akpm@xxxxxxxxxxxxxxxxxxxx>
> *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@xxxxxxxxxx>
> > ---
> >    fs/ocfs2/suballoc.c | 146 ++++++++++++++++++++++++++++----------------
> >    1 file changed, 95 insertions(+), 51 deletions(-)