From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 073524DB54A; Thu, 23 Jul 2026 13:58:56 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784815145; cv=none; b=c73YRKk+6Kp0xEJUWoED+ijBuwQJbBzT9QEf3fnVPp6vRQ8PsFmWVfUtkUyjdrpeWixcLFrTmHeUedDHosyjUar/pyaCSpoJsMWEeGNoeXCNuhK8oVo6IsRfE/75CBdJTwkdVddgopc401CojdKUAfy/PkqIeLiR4y3iowrssFs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784815145; c=relaxed/simple; bh=dPISo5F5Xw1PfBlOBSFPQUSkHdg5cx0n5Ru7nwTbrrU=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=Xc9WPyJnxW/Qo1rr8dkYG2kzeYMCK7ZcOsNSQdB8HaRfRHWTh2Wl9oBsoeJzX15WgAHP03hrpMl2+DE435kcdgT8f/nNk98QYmy/Jpqtmdi84o28WxtmfuwihntJmM5TYBbTtz7BhD1l2Q/F40puliyd60gLEvFyHzq8vkCgX0U= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=ERhMjkmW; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="ERhMjkmW" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7957A1F000E9; Thu, 23 Jul 2026 13:58:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1784815133; bh=RN1NtJOwTVSgpxHY//v/9VWJtoDg49Eyw88g5AHlfDs=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=ERhMjkmWNoCfLWJJQZYrRy9rnbdsyN2ndJnz65r0gmZHV2dzuPimeFSJS1ThfaCW5 OSnzQ5XTdmEevYnfLqu+3uwd9ludS8elGYRokfxdFGEkzCmEEwy9QX9a8NZ1FJN1Cp HJ7OmSHeDjOD5B521Dm861rYuX6zcz/LIpQLLA8e+ef4DDiMjK+sH48o9NtjUjtQWE dEIRGkUhZV6dLvnTKG1iWDWg2IOohBPIc1fiDZA5QZbZOjE3jyoAz+2yXOgrYSsHrK eATPih/9roizU6pyIHir7VLisS5+8EiHDY7TpDLV7RFZVNzErwnScZpT4LzOd3bf2M cSJz/u4bquQ1g== Message-ID: <04d259ed-a874-435d-9046-cca55856fd60@kernel.org> Date: Thu, 23 Jul 2026 15:58:47 +0200 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 v2] mm/slub: fix missing debugfs entries for caches created before sysfs init Content-Language: en-US To: Li Xiasong , Harry Yoo , Andrew Morton Cc: stable@vger.kernel.org, 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: <20260723115532.761920-1-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: <20260723115532.761920-1-lixiasong1@huawei.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 7/23/26 13:55, 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 miss their debugfs > entries because do_kmem_cache_create() skips debugfs_slab_add() when > slab_state <= UP. > > The affected window is: > > slab_debugfs_init() > slab_debugfs_root = debugfs_create_dir(...) > list_for_each_entry(s, &slab_caches, list) > debugfs_slab_add(s) > > kmem_cache_create(..., SLAB_STORE_USER, ...) > do_kmem_cache_create() > if (slab_state <= UP) > return without debugfs entries > > slab_sysfs_init() > slab_state = FULL > > Initialize the debugfs root and add debugfs entries while > slab_sysfs_init() holds slab_mutex and walks slab_caches. This gives the > sysfs and debugfs initialization an explicit order and prevents caches > from being created between the debugfs scan and slab_state reaching > FULL. > > Since the debugfs root is now initialized later, a cache may be released > before the root exists. Guard debugfs_slab_release() in that case to > avoid looking up the cache name in the debugfs root directory. > > Fixes: 1a5ad30b89b4 ("mm: slub: make slab_sysfs_init() a late_initcall") > Cc: stable@vger.kernel.org > Signed-off-by: Li Xiasong This is better, thanks. But I think now we have a problem that debugfs enabled and sysfs disabled (which is possible), debugfs will not be initialized. So we might need a more generically named late_initcall function that's executed with either sysfs or debugfs enabled, and wrap slab_kset creation and alias_list processing in functions that have an empty no-sysfs variant. > --- > > Changes in v2: > - Move debugfs root and cache entry initialization into > slab_sysfs_init() so both use the same mutex-protected cache walk. > - Guard debugfs_slab_release() against an uninitialized debugfs root. > - Update the commit message accordingly. > > v1: https://lore.kernel.org/linux-mm/20260720145124.3684976-1-lixiasong1@huawei.com/ > > --- > mm/slub.c | 22 +++++++++++----------- > 1 file changed, 11 insertions(+), 11 deletions(-) > > diff --git a/mm/slub.c b/mm/slub.c > index 9ec774dc7009..70e9aeda6a8f 100644 > --- a/mm/slub.c > +++ b/mm/slub.c > @@ -339,8 +339,10 @@ static inline int sysfs_slab_add(struct kmem_cache *s) { return 0; } > > #if defined(CONFIG_DEBUG_FS) && defined(CONFIG_SLUB_DEBUG) > static void debugfs_slab_add(struct kmem_cache *); > +static void __init slab_debugfs_root_init(void); > #else > static inline void debugfs_slab_add(struct kmem_cache *s) { } > +static inline void slab_debugfs_root_init(void) { } > #endif > > enum add_mode { > @@ -9771,11 +9773,16 @@ static int __init slab_sysfs_init(void) > > slab_state = FULL; > > + slab_debugfs_root_init(); > + > list_for_each_entry(s, &slab_caches, list) { > err = sysfs_slab_add(s); > if (err) > pr_err("SLUB: Unable to add boot slab %s to sysfs\n", > s->name); > + > + if (s->flags & SLAB_STORE_USER) > + debugfs_slab_add(s); > } > > while (alias_list) { > @@ -9985,23 +9992,16 @@ static void debugfs_slab_add(struct kmem_cache *s) > > void debugfs_slab_release(struct kmem_cache *s) > { > + if (unlikely(!slab_debugfs_root)) > + return; > + > debugfs_lookup_and_remove(s->name, slab_debugfs_root); > } > > -static int __init slab_debugfs_init(void) > +static void __init slab_debugfs_root_init(void) > { > - struct kmem_cache *s; > - > 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); > - > - return 0; > - > } > -__initcall(slab_debugfs_init); > #endif > /* > * The /proc/slabinfo ABI