linux-ext4 - Re: [PATCH] ext4: replace kmem_cache_create with KMEM

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Message-ID: <Y2xmRmGY7lfg/sbt@sol.localdomain>
Date:   Wed, 9 Nov 2022 18:47:34 -0800
From:   Eric Biggers <ebiggers@...nel.org>
To:     JunChao Sun <sunjunchao2870@...il.com>
Cc:     linux-ext4@...r.kernel.org, tytso@....edu,
        adilger.kernel@...ger.ca, jack@...e.cz
Subject: Re: [PATCH] ext4: replace kmem_cache_create with KMEM_CACHE

On Thu, Nov 10, 2022 at 08:53:26AM +0800, JunChao Sun wrote:
> Yeah, maybe we should remove the SLAB_RECLAIM_ACCOUNT flag for static
> slab, and 16828088f9e51815 ("ext4: use KMEM_CACHE instead of
> kmem_cache_create") have done so. But should we remove
> SLAB_RECLAIM_ACCOUNT in this patch or belong to a separate patch?

I'd just keep the slab flags the same in this patch.  If any flags do need to be
changed, that should be a separate patch.

I think SLAB_RECLAIM_ACCOUNT is meant for for things that are directly
reclaimable, such as struct ext4_inode_info.  Inodes are evictable, and when
that happens, the corresponding struct ext4_inode_info gets freed.

bio_post_read_ctx_cache probably should use SLAB_TEMPORARY instead, since it is
only used for temporary structures during I/O.

That being said, SLAB_TEMPORARY is currently #define'd to SLAB_RECLAIM_ACCOUNT,
so currently it makes no difference in practice...

- Eric