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From: Shakeel Butt To: "Kirill A. Shutemov" Cc: Andrew Morton , David Hildenbrand , lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, vbabka@suse.cz, rppt@kernel.org, surenb@google.com, mhocko@suse.com, hannes@cmpxchg.org, muchun.song@linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Randy Dunlap , Konstantin Khlebnikov Subject: Re: [PATCH] mm/vmstat: Fix build with MEMCG=y and VM_EVENT_COUNTERS=n Message-ID: References: <20250604095111.533783-1-kirill.shutemov@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250604095111.533783-1-kirill.shutemov@linux.intel.com> X-Migadu-Flow: FLOW_OUT X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 8B59A8000A X-Stat-Signature: pyh59e8n8fgyatz9m3m13bxwycdcsuy3 X-Rspam-User: X-HE-Tag: 1749052194-57215 X-HE-Meta: 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 sm2VwACQ kQJBzKPUHtGnpR1lGTcYmoDJ0Pvp8tVK1pwflGAXJEoXll/7C5rM7X9hqkuey/PCSlUjsEIhHrUyDNRfd9Iv7jofBIsOHRDybwph9Bf99iMPXo26ebWL1GzcwoxE7PAvl4eqL8yjY+cUpFBYd7vRYqxMgISKVhhejkUEx0kxbXY5VcFaP+0gk6JGE01YNxWpOt2K+bS68sa/+liereHDkT2OFi0u5T1TVZAi1ot6zIORdrHEoLdVXyJtNOdQOS8ctfFxp9Z9P4JWUBYVJ7zaK2ztQsU1yWAk4mJ7jcymni8uv2zzgnFecPG0s/3Xz21B9Kql4E545fLFHxumt0k1EkFYhNzWQAG9r1X6LpiuF+qFROLngAAKzmStUKw== 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, Jun 04, 2025 at 12:51:11PM +0300, Kirill A. Shutemov wrote: > When compiling with MEMCG enabled but VM_EVENT_COUNTERS disabled, > BUILD_BUG_ON() is triggered in vmstat_start because the vmstat_text > array is larger than NR_VMSTAT_ITEMS. > > This issue arises because some elements of the vmstat_text array are > present when either MEMCG or VM_EVENT_COUNTERS is enabled, but > NR_VMSTAT_ITEMS only accounts for these elements if VM_EVENT_COUNTERS is > enabled. > > The recent change in the BUILD_BUG_ON() check made it more strict, > disallowing extra elements in the array, which revealed the issue. > > Instead of adjusting the NR_VMSTAT_ITEMS definition to account for > MEMCG, make MEMCG select VM_EVENT_COUNTERS. VM_EVENT_COUNTERS is > enabled in most configurations anyway. > > There is no need to backport this fix to stable trees. Without the > strict BUILD_BUG_ON(), the issue is not harmful. The elements in > question would only be read by the memcg code, not by /proc/vmstat. > > Signed-off-by: Kirill A. Shutemov > Reported-by: Randy Dunlap > Fixes: ebc5d83d0443 ("mm/memcontrol: use vmstat names for printing statistics") > Cc: Konstantin Khlebnikov Acked-by: Shakeel Butt