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bh=UGuntV3J1idHYlamoG5JcaZ3RKqpek8czi0dvq5gqps=; b=446vAx/sOr3QbHgE+/e4MkYKT6AEemfBAQM30r+Ybs96pXndLkdflt0KWNaOHJp1I/2FWi k3ap2N9i/vxAHbCg== Received: from imap1.dmz-prg2.suse.org (localhost [127.0.0.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by imap1.dmz-prg2.suse.org (Postfix) with ESMTPS id 4F3293EA63; Wed, 7 Jan 2026 13:54:16 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id Wz38EohlXmkxIgAAD6G6ig (envelope-from ); Wed, 07 Jan 2026 13:54:16 +0000 Message-ID: Date: Wed, 7 Jan 2026 14:54:15 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH V5 3/8] ext4: specify the free pointer offset for ext4_inode_cache Content-Language: en-US To: Harry Yoo , akpm@linux-foundation.org Cc: andreyknvl@gmail.com, cl@gentwo.org, dvyukov@google.com, glider@google.com, hannes@cmpxchg.org, linux-mm@kvack.org, mhocko@kernel.org, muchun.song@linux.dev, rientjes@google.com, roman.gushchin@linux.dev, ryabinin.a.a@gmail.com, shakeel.butt@linux.dev, surenb@google.com, vincenzo.frascino@arm.com, yeoreum.yun@arm.com, tytso@mit.edu, adilger.kernel@dilger.ca, linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, hao.li@linux.dev References: <20260105080230.13171-1-harry.yoo@oracle.com> <20260105080230.13171-4-harry.yoo@oracle.com> From: Vlastimil Babka Autocrypt: addr=vbabka@suse.cz; 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DKIM_TRACE(0.00)[suse.cz:+]; DBL_BLOCKED_OPENRESOLVER(0.00)[imap1.dmz-prg2.suse.org:rdns,imap1.dmz-prg2.suse.org:helo] X-Rspamd-Server: rspamd1.dmz-prg2.suse.org X-Rspamd-Action: no action X-Spam-Level: On 1/5/26 09:02, Harry Yoo wrote: > Convert ext4_inode_cache to use the kmem_cache_args interface and > specify a free pointer offset. > > Since ext4_inode_cache uses a constructor, the free pointer would be > placed after the object to overwriting fields used by the constructor. ^ prevent? > However, some fields such as ->i_flags are not used by the constructor > and can safely be repurposed for the free pointer. > > Specify the free pointer offset at i_flags to reduce the object size. > > Signed-off-by: Harry Yoo > --- > fs/ext4/super.c | 20 ++++++++++++++------ > 1 file changed, 14 insertions(+), 6 deletions(-) > > diff --git a/fs/ext4/super.c b/fs/ext4/super.c > index 87205660c5d0..42580643a466 100644 > --- a/fs/ext4/super.c > +++ b/fs/ext4/super.c > @@ -1491,12 +1491,20 @@ static void init_once(void *foo) > > static int __init init_inodecache(void) > { > - ext4_inode_cachep = kmem_cache_create_usercopy("ext4_inode_cache", > - sizeof(struct ext4_inode_info), 0, > - SLAB_RECLAIM_ACCOUNT | SLAB_ACCOUNT, > - offsetof(struct ext4_inode_info, i_data), > - sizeof_field(struct ext4_inode_info, i_data), > - init_once); > + struct kmem_cache_args args = { > + .align = 0, Nit: it's implicit so not necessary. > + .useroffset = offsetof(struct ext4_inode_info, i_data), > + .usersize = sizeof_field(struct ext4_inode_info, i_data), > + .use_freeptr_offset = true, > + .freeptr_offset = offsetof(struct ext4_inode_info, i_flags), > + .ctor = init_once, > + }; > + > + ext4_inode_cachep = kmem_cache_create("ext4_inode_cache", > + sizeof(struct ext4_inode_info), > + &args, > + SLAB_RECLAIM_ACCOUNT | SLAB_ACCOUNT); > + > if (ext4_inode_cachep == NULL) > return -ENOMEM; > return 0;