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b=McJ1vp32QXe9xyBY23YUYPFogGoBVy/82ac1XL5PM6v0WtDEP6fZJMyj4G+3m1dcM M8Mg9aWMQgjvNShH83Jl/da4+akt8v10TLkbKooVpo9iajU9jeWER2ZLHWiIHetOqo QjhhOfTxaZLcl9fqfOnPFJh0nKU3+Dx4yQWVyVNKnC+6S4nIQuLJlIFZ8MxdVos3qJ 4uYlGQWvP6+GJzvWi2WkAWg9ktm0BFb4f777Mdcuv+mCLOfS493+WGsoGZS0lJU0kb iXvkOPqUdmb84Ed30xiPSXpuxCRB2zbHKavO4hkrCWaYCFccZYnp5sN5hMlGs0Go26 Cr3cq/BOefBIw== From: Pratyush Yadav To: Mike Rapoport Cc: Pratyush Yadav , Pasha Tatashin , Andrew Morton , linux-kernel@vger.kernel.org, linux-mm@kvack.org, stable@vger.kernel.org Subject: Re: [PATCH 1/2] mm: memfd_luo: always make all folios uptodate In-Reply-To: (Mike Rapoport's message of "Wed, 25 Feb 2026 10:53:30 +0200") References: <20260223173931.2221759-1-pratyush@kernel.org> <20260223173931.2221759-2-pratyush@kernel.org> Date: Thu, 05 Mar 2026 09:50:18 +0100 Message-ID: <2vxzqzpybqyd.fsf@kernel.org> User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 Content-Type: text/plain X-Rspam-User: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 3246740003 X-Stat-Signature: ryfnohc33ekh1z9i58jn9m1grgmrxxjo X-HE-Tag: 1772700622-357836 X-HE-Meta: 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Feb 25 2026, Mike Rapoport wrote: > On Mon, Feb 23, 2026 at 06:39:28PM +0100, Pratyush Yadav wrote: [...] >> + >> + /* >> + * If the folio is not uptodate, it was fallocated but never >> + * used. Saving this flag at prepare() doesn't work since it >> + * might change later when someone uses the folio. >> + * >> + * Since we have taken the performance penalty of allocating, >> + * zeroing, and pinning all the folios in the holes, take a bit >> + * more and zero all non-uptodate folios too. >> + * >> + * NOTE: For someone looking to improve preserve performance, >> + * this is a good place to look. > > I'd add a larger comment above memfd_luo_preserve_folios() that says that > it allocates, pins etc and fold the last two paragraphs of this comment > there. How about this: /* * If the folio is not uptodate, it was fallocated but never * used. Saving this flag at prepare() doesn't work since it * might change later when the folio is used. Make it uptodate * now to avoid this problem. */ if (!folio_test_uptodate(folio)) { And the comment above memfd_pin_folios() gets this: * NOTE: For someone looking to improve preserve performance, this is a * good place to look. Also look at the folio zeroing below. [...] -- Regards, Pratyush Yadav