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Wed, 24 Sep 2025 06:06:33 -0400 (EDT) Date: Wed, 24 Sep 2025 11:06:31 +0100 From: Kiryl Shutsemau To: David Hildenbrand Cc: Wei Yang , akpm@linux-foundation.org, lorenzo.stoakes@oracle.com, ziy@nvidia.com, baolin.wang@linux.alibaba.com, Liam.Howlett@oracle.com, npache@redhat.com, ryan.roberts@arm.com, dev.jain@arm.com, baohua@kernel.org, lance.yang@linux.dev, xu.xin16@zte.com.cn, chengming.zhou@linux.dev, linux-mm@kvack.org, Dan Carpenter Subject: Re: [Patch v3 1/2] mm/ksm: get mm_slot by mm_slot_entry() when slot is !NULL Message-ID: References: <20250924004854.29889-1-richard.weiyang@gmail.com> <20250924004854.29889-2-richard.weiyang@gmail.com> <27storxu4seijr5smul3xx7pofe45ittjrchii3jtwbntalsiy@2cu3wf42drwa> <1ebbfe02-1cb5-4f7a-a640-68d5d95cb99b@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1ebbfe02-1cb5-4f7a-a640-68d5d95cb99b@redhat.com> X-Rspamd-Queue-Id: E63E0120010 X-Rspam-User: X-Rspamd-Server: rspam07 X-Stat-Signature: bpeceqtx7c3jao97qi5dnzfqqwmzwxw1 X-HE-Tag: 1758708395-907404 X-HE-Meta: U2FsdGVkX18Esya4psVCWnRqjlmbgIXQ4fAVdUNmqeMkoQ32XBqft4PwP+u2KhQjiv76wL3ABWL/3OaQEFhEkutkhGHV8In2N8H2gv6qDf0NKpv0HJyryVmCSrN4PNSPKmi1qRfmKIPBy6cZ/bTsal5Kz2+KD8K3xu61/nCxYyVvVEMGEhBWCt+d4u2kyfL3U9TyEG368SofVxjuR0DSmJssOGLMY8Mb7xsbY6t9SNBdoHwDJRcKQKdk/9nTnmgiutqIAUPoB41gSs6uUeYbYqTnD3GPcGcl6VX6BQxZ7wMEP0k7+ElIDVyvX8K05qnmZ43NejvmqDmjfR/LGAZM/WzUAMieqDIjjFUpndLjVMvAnOTYFVJSZ4L6Hld0gNXksn0qFmaIoMJ9Bxw0rqvHDnjb7KHBBK7c6R62zllQG96iBYWs2UNiRvCLUuyc2o8xGAZbuB1Tmw58e/AZVGvAIOR1ET8ZyzsPLdVtqYeNJkRNK5+Gjsh4sLlbOswQ7v8AYZItvHtPlVm6mWX0f33v/QgjkZ9uk74MOo5g+OfsV0zzC3MjGamggrC8Qpehcv3WO7Swvv4qbNE9Gd+U0+DsvtfHfZtq7OzbqAwBQk45+RoUzuq74BR9LMaRTbRGQWW7Wm5v4BVnNhpxyhZjPPOrX5J+EgKHyyalcRINNKiHx8tmnnRl9oa5CIWbmzS/kCbT5tg1BkbhiCRsiYAut3edsr2lYfnSlK6mtJfP1K1+nbwftA7gMeuBmkwx0kQNQe0yJpVpGUQe9CwhTmDxaJLb5iEkR17T8DHDU8H5HRg3H+qNRWJX/3oYkNs7SOWREGrmVvyyepOODFtfaDSxM/iBRR8lSEpuzPV57yvPXmainSheoBhRGuKgPjW26aHmtMGeTN0YmsoMYsSNj56AVVxyQFMgBwMeXXknLfSI6LLjnNeT1kJsnFdI15kc7m1ZzlbxOxKygR6NPI/TC0JgWtL IVZvJ3lt 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 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 Wed, Sep 24, 2025 at 11:40:21AM +0200, David Hildenbrand wrote: > On 24.09.25 11:35, Kiryl Shutsemau wrote: > > On Wed, Sep 24, 2025 at 12:48:53AM +0000, Wei Yang wrote: > > > Patch series "mm_slot: fix the usage of mm_slot_entry", v2. > > > > > > When using mm_slot in ksm, there is code like: > > > > > > slot = mm_slot_lookup(mm_slots_hash, mm); > > > mm_slot = mm_slot_entry(slot, struct ksm_mm_slot, slot); > > > if (mm_slot && ..) { > > > } > > > > > > The mm_slot_entry() won't return a valid value if slot is NULL generally. > > > But currently it works since slot is the first element of struct > > > ksm_mm_slot. > > > > > > To reduce the ambiguity and make it robust, access mm_slot_entry() when > > > slot is !NULL. > > > > > > Signed-off-by: Wei Yang > > > Acked-by: David Hildenbrand > > > Reviewed-by: Dev Jain > > > Reviewed-by: Lance Yang > > > Cc: Kiryl Shutsemau > > > Cc: xu xin > > > Cc: Dan Carpenter > > > > > > --- > > > v3: > > > * fix uninitialized mm_slot > > > --- > > > mm/ksm.c | 22 ++++++++++++---------- > > > 1 file changed, 12 insertions(+), 10 deletions(-) > > > > > > diff --git a/mm/ksm.c b/mm/ksm.c > > > index 2dbe92e3dd52..c00a21800067 100644 > > > --- a/mm/ksm.c > > > +++ b/mm/ksm.c > > > @@ -2921,7 +2921,7 @@ int __ksm_enter(struct mm_struct *mm) > > > void __ksm_exit(struct mm_struct *mm) > > > { > > > - struct ksm_mm_slot *mm_slot; > > > + struct ksm_mm_slot *mm_slot = NULL; > > > struct mm_slot *slot; > > > int easy_to_free = 0; > > > @@ -2936,15 +2936,17 @@ void __ksm_exit(struct mm_struct *mm) > > > spin_lock(&ksm_mmlist_lock); > > > slot = mm_slot_lookup(mm_slots_hash, mm); > > > - mm_slot = mm_slot_entry(slot, struct ksm_mm_slot, slot); > > > - if (mm_slot && ksm_scan.mm_slot != mm_slot) { > > > - if (!mm_slot->rmap_list) { > > > - hash_del(&slot->hash); > > > - list_del(&slot->mm_node); > > > - easy_to_free = 1; > > > - } else { > > > - list_move(&slot->mm_node, > > > - &ksm_scan.mm_slot->slot.mm_node); > > > + if (slot) { > > > + mm_slot = mm_slot_entry(slot, struct ksm_mm_slot, slot); > > > + if (ksm_scan.mm_slot != mm_slot) { > > > + if (!mm_slot->rmap_list) { > > > + hash_del(&slot->hash); > > > + list_del(&slot->mm_node); > > > + easy_to_free = 1; > > > + } else { > > > + list_move(&slot->mm_node, > > > + &ksm_scan.mm_slot->slot.mm_node); > > > + } > > > > Indent level gets extreme. > > You call this extreme? :) Emphasis on "gets". :) -- Kiryl Shutsemau / Kirill A. Shutemov