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Fri, 24 Mar 2023 17:30:03 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id BiLnBBveHWQ8LQAAMHmgww (envelope-from ); Fri, 24 Mar 2023 17:30:03 +0000 Message-ID: <22a1ec75-155a-2392-ce39-4bca3fc081eb@suse.cz> Date: Fri, 24 Mar 2023 18:30:02 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.9.0 Subject: Re: [PATCH] mm/mempolicy: Fix exception handling in shared_policy_replace() Content-Language: en-US To: Markus Elfring , kernel-janitors@vger.kernel.org, linux-mm@kvack.org, Andrew Morton , Kosaki Motohiro , Mel Gorman Cc: cocci@inria.fr, LKML References: <6e9ca062-939b-af96-c8ff-56ad485d6e79@web.de> From: Vlastimil Babka In-Reply-To: <6e9ca062-939b-af96-c8ff-56ad485d6e79@web.de> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: C49E0A001F X-Stat-Signature: gybd7wtke88xks44fufufqsrmne4rufh X-Rspam-User: X-HE-Tag: 1679679004-308981 X-HE-Meta: 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 KQ3wa0Ql 6LiYwQ8OVU2AiWwjiwrppRuwWCfQLJUmY4Cy+cuOBC/UvMzG7ZYYAzCvIqz5kqTb+oOBjherN1fg4ipds1K6MK38C0ugsPuxpG5QbNdRcGfl/D8jXdDEhAxx3mXtUAr/wj/mhbV6tSKct8MV6x5Ufn0XrvRxAMx/fw5pPkDv1z5Cm+mM6mPmTC0ZPJ9DepH/z/pvVXRtvKPNryvRWsz86hJ+j0aqFS3Dk22HbitxynuFpvkJvJTe2R2k8Gun8Xf27wjQ6fLl20LbWA3mSkzXlq6F7k7D/YhMj/mbIAORNxSKFqhhWlw5cKjZfT+PHoPaexVcFoy7tSOreapkwfrr3G/ThUg== 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: Your patch doesn't apply, seems like it uses spaces instead of tabs. Also I can't use 'b4' to download it as there are multiple different patches using the same message-id: https://lore.kernel.org/all/6e9ca062-939b-af96-c8ff-56ad485d6e79@web.de/ Re: subject, I don't see a bug that this would fix. You could say it's "cleanup" and this function could use one, but for a cleanup it's not improving the situation much. On 3/23/23 18:30, Markus Elfring wrote: > Date: Thu, 23 Mar 2023 18:18:59 +0100 > > The label “err_out” was used to jump to another pointer check despite of > the detail in the implementation of the function “shared_policy_replace” > that it was determined already that a corresponding variable contained a > null pointer because of a failed call of the function “kmem_cache_alloc”. > > 1. Use more appropriate labels instead. > > 2. The implementation of the function “mpol_put” contains a pointer check >    for its single input parameter. >    Thus delete a redundant check in the caller. > > > This issue was detected by using the Coccinelle software. > > Fixes: 42288fe366c4f1ce7522bc9f27d0bc2a81c55264 ("mm: mempolicy: Convert shared_policy mutex to spinlock") Again this is not a fix. > Signed-off-by: Markus Elfring > --- >  mm/mempolicy.c | 11 +++++------ >  1 file changed, 5 insertions(+), 6 deletions(-) > > diff --git a/mm/mempolicy.c b/mm/mempolicy.c > index a256a241fd1d..fb0485688dcb 100644 > --- a/mm/mempolicy.c > +++ b/mm/mempolicy.c > @@ -2736,13 +2736,12 @@ static int shared_policy_replace(struct shared_policy *sp, unsigned long start, >          sp_insert(sp, new); >      write_unlock(&sp->lock); >      ret = 0; > +put_mpol: > +    mpol_put(mpol_new); >   > -err_out: > -    if (mpol_new) > -        mpol_put(mpol_new); >      if (n_new) >          kmem_cache_free(sn_cache, n_new); > - > +exit: >      return ret; >   >  alloc_new: > @@ -2750,10 +2749,10 @@ static int shared_policy_replace(struct shared_policy *sp, unsigned long start, >      ret = -ENOMEM; >      n_new = kmem_cache_alloc(sn_cache, GFP_KERNEL); >      if (!n_new) > -        goto err_out; > +        goto exit; Just "return ret" and no need for exit label? >      mpol_new = kmem_cache_alloc(policy_cache, GFP_KERNEL); >      if (!mpol_new) > -        goto err_out; > +        goto put_mpol; We are doing this because mpol_new == NULL, so we know there's no reason to do mpol_put(), we could jump to the freeing of n_new. >      atomic_set(&mpol_new->refcnt, 1); >      goto restart; >  } > -- > 2.40.0 > > >