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b=D6TlA/dC/7ffmyD5i48P0Qkq1eu/nEwWvhrYfF/MO3udrUcJiWVSXuFzDt8V1UFPF 7DJUFsHU+7hH5DzG+rmIa6TgkJwaVqR4JLen4tyQgNnRg4+xtQd5escB1iUZR+Bl6F eL/f+wnqRp2DCbX4mH1YdcINpVCI3LuG++qm3A/nNnVgE6OUwHjga0pQr0SdMzjmDk 6GIPLcDHPMmhtgGDLcsjfy1uVTg8bSZlGIYOHp+pRRkGq7ZvEjfUh5zSp4xxroewdm AG6Z3DM3eJm5n0qLLTKgufE2G2XKkKSwWhSFJXy1HfPkO7Q3RIh9hbUw7nBwzl3hwu bdi9X8uQ5sPOA== Message-ID: Date: Mon, 20 Jul 2026 22:39:03 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/slub: fix missing debugfs entries for caches created before sysfs init Content-Language: en-US To: Li Xiasong , Harry Yoo , Andrew Morton Cc: Hao Li , Christoph Lameter , David Rientjes , Roman Gushchin , Rasmus Villemoes , linux-mm@kvack.org, linux-kernel@vger.kernel.org, yuehaibing@huawei.com, zhangchangzhong@huawei.com, weiyongjun1@huawei.com References: <20260720145124.3684976-1-lixiasong1@huawei.com> From: "Vlastimil Babka (SUSE)" Autocrypt: addr=vbabka@kernel.org; keydata= xsFNBFZdmxYBEADsw/SiUSjB0dM+vSh95UkgcHjzEVBlby/Fg+g42O7LAEkCYXi/vvq31JTB KxRWDHX0R2tgpFDXHnzZcQywawu8eSq0LxzxFNYMvtB7sV1pxYwej2qx9B75qW2plBs+7+YB 87tMFA+u+L4Z5xAzIimfLD5EKC56kJ1CsXlM8S/LHcmdD9Ctkn3trYDNnat0eoAcfPIP2OZ+ 9oe9IF/R28zmh0ifLXyJQQz5ofdj4bPf8ecEW0rhcqHfTD8k4yK0xxt3xW+6Exqp9n9bydiy tcSAw/TahjW6yrA+6JhSBv1v2tIm+itQc073zjSX8OFL51qQVzRFr7H2UQG33lw2QrvHRXqD Ot7ViKam7v0Ho9wEWiQOOZlHItOOXFphWb2yq3nzrKe45oWoSgkxKb97MVsQ+q2SYjJRBBH4 8qKhphADYxkIP6yut/eaj9ImvRUZZRi0DTc8xfnvHGTjKbJzC2xpFcY0DQbZzuwsIZ8OPJCc LM4S7mT25NE5kUTG/TKQCk922vRdGVMoLA7dIQrgXnRXtyT61sg8PG4wcfOnuWf8577aXP1x 6mzw3/jh3F+oSBHb/GcLC7mvWreJifUL2gEdssGfXhGWBo6zLS3qhgtwjay0Jl+kza1lo+Cv BB2T79D4WGdDuVa4eOrQ02TxqGN7G0Biz5ZLRSFzQSQwLn8fbwARAQABzSNWbGFzdGltaWwg QmFia2EgPHZiYWJrYUBrZXJuZWwub3JnPsLBsAQTAQoAWhYhBKlA1DSZLC6OmRA9UCJPp+fM gqZkBQJqFFy6GxSAAAAAAAQADm1hbnUyLDIuNSsxLjEyLDIsMgIbAwUJGtCBUAULCQgHAwUV CgkICwUWAgMBAAIeBQIXgAAKCRAiT6fnzIKmZJIUEADFx/tREzUImHrEwVHeSvDFmA7tJysI UVrlvrM09E7GIuzphzv7jYmo8n3ANpCczLEVr4G0syYQdTigaZgv3+FQDIIzhKih1IHhu1Ei XHlywNWKnQxxQEUNi5Mwx43wQz5XVw9F1A7gtKBKNtfogO511hAbrzagrYajyQacEJ/+sfhZ 9Da8ltHIXD8pcYaHUfQgEusCgmEd9+KrUwrTbckFKmYq5chuE6yJ4J0EmWknL096jIE6CnzF FRslQ3B1UKDjxVsm1ZHfir5NeWszLkTvGFsddFaWTgh8UycESG6VQzKXjjewXu2pG7YQYRpj QKm1W5X2TkwWkXRBZTmfmbhxIUMh3+zf5wQ463rSmDN/8v81tdqBtAW6rH/kzg1GvkaTHXn0 507yEHFzBksk2viAuIxxr7km8+/KARYLIdGtx30EG8cKzAUZOK6WqxtNCsXUJNrVE8CWrCaD icoNu7Fs1c5hmPHdSTnU48ce67449DdnO4neLSNhRiGlMHJgfJUmgrxu/hcYeOZ3haWmEQ2w uW1Mh01OHi8QZHCEyAbABrPs9GUgccc/4eYXX9hIgxfSkYzn8f+8NuIFPWl/0uTvjgqU29FQ SbzOLxHq9439Ox40G5mS5eZXRGxITYR+6TXvRGI6P/264jvflnr/pDGUttaikU+0W+1uxgKH cmYbEc7ATQRbGTU1AQgAn0H6UrFiWcovkh6EXVcl+SeqyO6JHOPm+e9Wu0Vw+VIUvXZVUVVQ La1PQDUi6j00ChlcR66g9/V0sPIcSutacPKfdKYOBvzd4rlhL8rfrdEsQw5ApZxrA8kYZVMh FmBRKAa6wos25moTlMKpCWzTH84+WO5+ziCTsTUZASAToz3RdunTD+vQcHj0GqNTPAHK63sf bAB2I0BslZkXkY1RLb/YhuA6E7JyEd2pilZOrIuBGl/5q2qSakgnAVFWFBR/DO27JuAksYnq +aH8vI0xGvwn75KqSk4UzAkDzWSmO4ZHuahKtQgZNsMYV+PGayRBX9b9zbldzopoLBdqHc4n jQARAQABwsF8BBgBCgAmAhsMFiEEqUDUNJksLo6ZED1QIk+n58yCpmQFAmfIHFQFCRYU6J8A CgkQIk+n58yCpmS2PA//bqN1LfcotmArgElsa+0EGZSQlYgK48pm8WAeTXTngudP9IJ4SuKY HR5RNjHcBeqN+Me0zxRqYzRb8nGanHEkDyf4Im8DQM8d6vbyU+FcPmG4skud4kgS1zMHnlVd SXfSIwKC/hKgdHG8aBV7545Lz9X6Iohea+94wneD0aw/hqF+QWewGZhWJriWAZtvEkzNjQOi 4U9F/trLten/x7bpphDSnDMKJtITbtzATT1Dq7o7VpIUK1nCTQALMuMjKCdi8OdU/+V+R3O4 0PXWvX8qrvqYapVbZ+9KqT74FsuB0Ya9uXwgBF2Q6cRuETZk5vqaqKxzqoQZCO8AOz/58j6O 2RHNy/mZEN+7tJ5Tsq42zVJ4jxsT8b9YplavCMsnBgDeRWhcbYhCyttoL7nYISyWg4kQYZ/P wIV3OuNv2f8iKYsxNsRuClOAF82+gvqOy1/1pprFjy8uo2pkoOrb63aOP3vO5VHnRKgra6dq NcaZ+c6J4H+nEJGi2SkHAUJz5oBzuThvPudLvPA/SK8sKoM01IRxSihev/S/5WLazXB1PGem OCbvzC1IjWJJraxiDJ5IygokapUa2RP7+WBR22skQ3SSl6G107QgWKSyTOGWEaRmV53vxQLV jXuCmzSSasTL60zq5yGrT4/DYQVSNEUiUbG4pYekxJujNeEDkUlky0Y= In-Reply-To: <20260720145124.3684976-1-lixiasong1@huawei.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Stat-Signature: 4stw88o3im94ow5mizr8c35qbk3k6jgi X-Rspam-User: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: DE2974000A X-HE-Tag: 1784579948-161808 X-HE-Meta: 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 2VIWqdsr Tl+FG6PrSN77pAaMiTNJQ9nV7Vqce71Ch8jy6WbpY1ojLR7OirQuesQP07PeqA7OgNb6TK9KzQtsljPkJ4t0yDEyv+UyfhyB7hS777/o8EHwIWR0nbBsLqDkzQbEs6jHOPw/l68vuP6QCL6DDYT3ffJsfr3SuG1PtJTgESRxEpzNpYM1ZnPAv+L/OPah2vcoCYu7cTNzOx30yLM0EzQXFzUavcr1ZLxMod1KTsKrFZekofua2ztt1U0kGrHwhvTW/N1gyZGLl6VP/4eoH7ePgWz9JC0w2K+N2x1QxoFhI/agwChXyoS5wrw/hP+YC8E56pD5i Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 7/20/26 16:51, Li Xiasong wrote: > slab_debugfs_init() creates the slab debugfs root at device > initcall time, while slab_sysfs_init() moves slab_state to FULL > at late initcall time. SLAB_STORE_USER caches created in this > window currently miss their debugfs entries because > do_kmem_cache_create() skips debugfs_slab_add() when slab_state > <= UP. This was observed with MPTCP's request_sock_subflow_v6 > cache, whose slab debugfs directory was missing. > > The affected initcall window is: > > slab_debugfs_init() > slab_debugfs_root = debugfs_create_dir(...) > > kmem_cache_create(..., SLAB_STORE_USER, ...) > do_kmem_cache_create() > if (slab_state <= UP) > return without debugfs entries > > slab_sysfs_init() > slab_state = FULL > > Run slab_debugfs_init() after slab_sysfs_init() and protect its scan of > slab_caches with slab_mutex. > > Fixes: 1a5ad30b89b4 ("mm: slub: make slab_sysfs_init() a late_initcall") > Signed-off-by: Li Xiasong Oops, good catch. Cc: stable perhaps? > --- > mm/slub.c | 9 ++++++++- > 1 file changed, 8 insertions(+), 1 deletion(-) > > diff --git a/mm/slub.c b/mm/slub.c > index 9ec774dc7009..d35e40c7a7ba 100644 > --- a/mm/slub.c > +++ b/mm/slub.c > @@ -9992,16 +9992,23 @@ static int __init slab_debugfs_init(void) > { > struct kmem_cache *s; > > + mutex_lock(&slab_mutex); > + > slab_debugfs_root = debugfs_create_dir("slab", NULL); > > list_for_each_entry(s, &slab_caches, list) > if (s->flags & SLAB_STORE_USER) > debugfs_slab_add(s); > > + mutex_unlock(&slab_mutex); > return 0; > > } > -__initcall(slab_debugfs_init); > +/* > + * This must be after slab_sysfs_init(), otherwise caches created between > + * the debugfs scan and slab_state reaching FULL miss their debugfs entries. > + */ > +late_initcall(slab_debugfs_init); Hm but does anything guarantee the ordering between late_initcall() is what we would want? Or it's possible we still miss something because the ordering could be: slab_debugfs_init() $some_other_late_initcall_fn() -> kmem_cache_create() slab_sysfs_init() What about a single late_initcall() function that walks the list once and calls both sysfs and debugfs parts? > #endif > /* > * The /proc/slabinfo ABI