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b=WM8sWNy+t/arfWSPsWRfTo7XmQhCgArwkS2Tc0vcFBAHtCEVSBQx05PqE8cKbCUB2 9KlAxBbJAMhG6YjFPas0TiXTYnEsCR/gplgrCn574V2HuRRIc7ZuJqDShLXNO+wfDh c09VAoR7Ovm+PLntCBtUIDjzMy//IXKHrPw22nVVRi6q6UdJd+bzmBaU6KidkqZi2x Lx6/6kFrhAJ2zDW874gAimMrfnAr3/D9d2zXDQKNbp5qLgCAJzk6qD/pgbZpl+WbyS ctq9FUBYpbyfNrD7vY6DUeF2Fsb+kjFw5kaim5GSKtDm2c3s4EMQFoKqgfzVElbBbk EHLHxVpsan3iQ== Date: Fri, 9 Oct 2026 13:00:52 +0100 From: "Lorenzo Stoakes (ARM)" To: Baolin Wang Cc: akpm@linux-foundation.org, david@kernel.org, liam@infradead.org, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, qi.zheng@linux.dev, jack@suse.cz, pfalcato@suse.de, ayushr@modal.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm: memory: fix truncation removing mapped folios Message-ID: References: <0d2a1809fa1cfc22ad3df26ec28b2d30e5cdf3bd.1791540483.git.baolin.wang@linux.alibaba.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <0d2a1809fa1cfc22ad3df26ec28b2d30e5cdf3bd.1791540483.git.baolin.wang@linux.alibaba.com> X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: EF2901C000F X-Rspam-User: X-Stat-Signature: 6woebrkp6uurfd1hmygiuiep3bqg7urc X-HE-Tag: 1791547259-323978 X-HE-Meta: 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 sIYDkUeP 0FAFvz4U8RslSbQ0vLcwySw8Qmozs9n8MK0ip0iTkesWPyK+SmbOvl4rzNUaP0BtulUjTgXMKBPP9MxYw40ftkJoH9LQ19VGKLKtQSooCGkRLKE001+rmrNm8nzPRuXDK6ev07BBGwWP+pAeQhSOggqvIwYMwhe4uddGn4f8dDlwn4czaNEloxQoACbe161sXC7tPDi6HYrWvu7uEBrVWvyCPSLNoLHxQkIoHPTbDoNFcKzFd/wU434nTxz6dQcDQR5ie Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, Oct 09, 2026 at 06:12:03PM +0800, Baolin Wang wrote: > diff --git a/mm/memory.c b/mm/memory.c > index 1f5d5f7d39cd..0272217ad7b0 100644 > --- a/mm/memory.c > +++ b/mm/memory.c > @@ -2044,16 +2053,10 @@ static unsigned long zap_pte_range(struct mmu_gather *tlb, > * to ensure they are still none, thereby preventing the pte entries > * from being repopulated by another thread. > */ > - if (can_reclaim_pt && direct_reclaim && addr == end) > + if (can_reclaim_pt && direct_reclaim && addr == end) { > + /* rmap changes need to be observed before e.g PTEs get zapped. */ > + smp_wmb(); What does this pair with? You should always say what in the comment. rmb/wmb are generally not needed vs. acquire/release. Are you sure a wmb is right here? -- Cheers, Lorenzo