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[2003:cb:c74d:4400:2f98:9b35:6822:ce54]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3912bfb7ae4sm1840309f8f.5.2025.03.06.04.13.23 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 06 Mar 2025 04:13:26 -0800 (PST) Message-ID: <2ad7973b-9d92-4b34-8534-73ed1164a1c8@redhat.com> Date: Thu, 6 Mar 2025 13:13:23 +0100 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: [RFC PATCH 1/4] mm: migrate: Allow misplaced migration without VMA too To: Bharata B Rao , linux-kernel@vger.kernel.org, linux-mm@kvack.org Cc: AneeshKumar.KizhakeVeetil@arm.com, Hasan.Maruf@amd.com, Jonathan.Cameron@huawei.com, Michael.Day@amd.com, akpm@linux-foundation.org, dave.hansen@intel.com, feng.tang@intel.com, gourry@gourry.net, hannes@cmpxchg.org, honggyu.kim@sk.com, hughd@google.com, jhubbard@nvidia.com, k.shutemov@gmail.com, kbusch@meta.com, kmanaouil.dev@gmail.com, leesuyeon0506@gmail.com, leillc@google.com, liam.howlett@oracle.com, mgorman@techsingularity.net, mingo@redhat.com, nadav.amit@gmail.com, nphamcs@gmail.com, peterz@infradead.org, raghavendra.kt@amd.com, riel@surriel.com, rientjes@google.com, rppt@kernel.org, shivankg@amd.com, shy828301@gmail.com, sj@kernel.org, vbabka@suse.cz, weixugc@google.com, willy@infradead.org, ying.huang@linux.alibaba.com, ziy@nvidia.com, dave@stgolabs.net, yuanchu@google.com, hyeonggon.yoo@sk.com References: <20250306054532.221138-1-bharata@amd.com> <20250306054532.221138-2-bharata@amd.com> From: David Hildenbrand Content-Language: en-US Autocrypt: addr=david@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 06.03.25 06:45, Bharata B Rao wrote: > migrate_misplaced_folio_prepare() can be called from a > context where VMA isn't available. Allow the migration > to work from such contexts too. I was initially confused about "can be called", because it can't Consider phrasing it as "We want to make use of alloc_misplaced_dst_folio() in context where we don't have VMA information available. To prepare for that ..." > > Signed-off-by: Bharata B Rao > --- > mm/migrate.c | 5 +++-- > 1 file changed, 3 insertions(+), 2 deletions(-) > > diff --git a/mm/migrate.c b/mm/migrate.c > index fb19a18892c8..5b21856a0dd0 100644 > --- a/mm/migrate.c > +++ b/mm/migrate.c > @@ -2639,7 +2639,8 @@ static struct folio *alloc_misplaced_dst_folio(struct folio *src, > > /* > * Prepare for calling migrate_misplaced_folio() by isolating the folio if > - * permitted. Must be called with the PTL still held. > + * permitted. Must be called with the PTL still held if called with a non-NULL > + * vma. > */ > int migrate_misplaced_folio_prepare(struct folio *folio, > struct vm_area_struct *vma, int node) > @@ -2656,7 +2657,7 @@ int migrate_misplaced_folio_prepare(struct folio *folio, > * See folio_likely_mapped_shared() on possible imprecision > * when we cannot easily detect if a folio is shared. > */ > - if ((vma->vm_flags & VM_EXEC) && > + if (vma && (vma->vm_flags & VM_EXEC) && > folio_likely_mapped_shared(folio)) > return -EACCES; > -- Cheers, David / dhildenb