From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id EE9BF39659A for ; Mon, 23 Mar 2026 12:20:17 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774268418; cv=none; b=Lutw3xILOrKSiBdfCO8ScNT0nu1sTlp0KfGTKyOBZxxudo+YpeJPIw2qJ984BGmUPzIzVswX6QNwGuE3GbC5t/T8iCPlArAK9r3u6MfYJgSHz1kJibNtwG9f5Wtu9Qg8bo6HOz0oiohbGVbhSMogMXyl9n+8luZE1zDCAYxVEfM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774268418; c=relaxed/simple; bh=q907mWmretck/dkDWY6czsLRkWpdZxdxZ34zLFmLAo4=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=umR8dSBXH56o6FLmEYHhQXtGSzIg1h9YMu70znnBPzprCX5OIipJLRc2rZzyrybNFpYDAc77sLSD3PtdDc1X0BprImSWNPuHVNkKERRNZx/KZggE2GmYEXQszZxhrhzInpW2ptGvgYPkOkTVoByMzYj9ouSb3Gm7naE7CmaNapk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=mBxJJpc0; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="mBxJJpc0" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7CFAFC2BCB1; Mon, 23 Mar 2026 12:20:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1774268417; bh=q907mWmretck/dkDWY6czsLRkWpdZxdxZ34zLFmLAo4=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=mBxJJpc0a/J/qXlh4wWG3qDWE4ieZbnSHK+x9tW8qtkWjOssiwWJ1tVKEaohonphl lUqG7s0u0H/KQQ7W0QoEMIiYFR0CLUrbIYz/SzS2YGiASQvW55Gi+p59TyCM1V13h8 14JsNDOW2uejTxYxVX0MNhn1s44gU6rzn7LMylITcHvdXdPDl7IOwAzcnTbPpHgqjF +LA6wvaSpkuik4y3XSNPIbQPZdc1Kbdtum9w5HMihvlnT1ppt5GDA89L10T+aPWBOm E+rO5UO5l8FCBrdjHSl8cCiejQw/I0Ai247DRAG3r6xckRxmvBjEqBUVUWwIUvlBNf YY5vAiqWgJWWw== Message-ID: Date: Mon, 23 Mar 2026 13:20:06 +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 v4 2/6] mm/migrate: skip data copy for already-copied folios To: "Garg, Shivank" , akpm@linux-foundation.org Cc: lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, vbabka@kernel.org, willy@infradead.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, ziy@nvidia.com, matthew.brost@intel.com, joshua.hahnjy@gmail.com, rakie.kim@sk.com, byungchul@sk.com, gourry@gourry.net, ying.huang@linux.alibaba.com, apopple@nvidia.com, dave@stgolabs.net, Jonathan.Cameron@huawei.com, rkodsara@amd.com, vkoul@kernel.org, bharata@amd.com, sj@kernel.org, weixugc@google.com, dan.j.williams@intel.com, rientjes@google.com, xuezhengchu@huawei.com, yiannis@zptcorp.com, dave.hansen@intel.com, hannes@cmpxchg.org, jhubbard@nvidia.com, peterx@redhat.com, riel@surriel.com, shakeel.butt@linux.dev, stalexan@redhat.com, tj@kernel.org, nifan.cxl@gmail.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org References: <20260309120725.308854-3-shivankg@amd.com> <20260309120725.308854-8-shivankg@amd.com> <4bfec2c1-9747-49d2-a490-87ab204cec1c@kernel.org> <99d3a0be-d33e-47c8-88b4-3f0e21f4a1cf@amd.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 3/15/26 19:25, Garg, Shivank wrote: > > > On 3/12/2026 3:14 PM, David Hildenbrand (Arm) wrote: >> On 3/9/26 13:07, Shivank Garg wrote: >>> Add a PAGE_ALREADY_COPIED flag to the dst->private migration state. >>> When set, __migrate_folio() skips folio_mc_copy() and performs >>> metadata-only migration. All callers currently pass >>> already_copied=false. The batch-copy path enables it in a later patch. >>> >>> Move the dst->private state enum earlier in the file so >>> __migrate_folio() and move_to_new_folio() can see PAGE_ALREADY_COPIED. >>> >>> Signed-off-by: Shivank Garg >>> --- >>> mm/migrate.c | 52 +++++++++++++++++++++++++++++++--------------------- >>> 1 file changed, 31 insertions(+), 21 deletions(-) >>> >>> diff --git a/mm/migrate.c b/mm/migrate.c >>> index 1bf2cf8c44dd..1d8c1fb627c9 100644 >>> --- a/mm/migrate.c >>> +++ b/mm/migrate.c >>> @@ -848,6 +848,18 @@ void folio_migrate_flags(struct folio *newfolio, struct folio *folio) >>> } >>> EXPORT_SYMBOL(folio_migrate_flags); >>> >>> +/* >>> + * To record some information during migration, we use unused private >>> + * field of struct folio of the newly allocated destination folio. >>> + * This is safe because nobody is using it except us. >>> + */ >>> +enum { >>> + PAGE_WAS_MAPPED = BIT(0), >>> + PAGE_WAS_MLOCKED = BIT(1), >>> + PAGE_ALREADY_COPIED = BIT(2), >>> + PAGE_OLD_STATES = PAGE_WAS_MAPPED | PAGE_WAS_MLOCKED | PAGE_ALREADY_COPIED, >> >> All these states really only apply to proper folios (not movable_ops). >> So once we complete decoupling movable_ops migration from folio >> migration, these flags would only appear in the folio migration part. >> >> Can we convert them first to state it clearly already that these are >> folio migration flags? >> >> FOLIO_MF_WAS_MAPPED >> >> ... >> > Sure, done. > > Should I fold it into the series? Or send it as independent patch as this series would > likely take few more rounds of reviews and discussion. Best to send it out as a standalone cleanup :) -- Cheers, David