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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 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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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Action: no action X-Rspamd-Server: rspam02 X-Stat-Signature: g5pizmjtsc8xjgrj4e9atdaqo548xxh9 X-Rspam-User: X-Rspamd-Queue-Id: 9A10240017 X-HE-Tag: 1767794059-8390 X-HE-Meta: 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 6nOTY6CU 07BYewoVm+GCjU4PDUwBIaAq1SRhxYfy+XJmr1OhFQo30oZ7xGcuw3D2eECZQmU1rF9Y6w+7drKmNDw10pCAEwyeRIw/mVrsWhS7R07LsXuiaDdTVzJ4VLhthoi5ic0audrq1RpezthCeJvqEq0YCUDJ/mWQtYEA5q0jgnuwf23Qvf+50QsgRnyXPt5WGDFgIQMJWwj7GKBfLquzXtQAHsqw6X1PLVI5v1jzcMXZpTs9Ajcq+o4QVyvZNy1S3VsV7jlP3f+cjavMFjlariBihdybOPxJ/WmVgkhM1smKplUMcXgbKg83dpUkcnjzuCJ/CgoMNSEwTzRS8qowfxqT2ZlhfMlIsan6hOzHncOLBAFLH1HdObVH1pZNr5Tsd3DK8Yy8QLgcXj0PWtdb6hNJbUF7B5WGQ1LVduCBLrIkzn3cFn8o= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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;