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charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: 7D4CF20020 X-Stat-Signature: nzaddhd4ju6ejq6x7ni14ayfdho375ky X-Rspam-User: X-Rspamd-Server: rspam06 X-HE-Tag: 1744121053-841579 X-HE-Meta: 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 yN/oPjKP 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 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 Mon Feb 3, 2025 at 6:53 PM UTC, Vishal Moola wrote: > On Thu, Jan 30, 2025 at 4:48=E2=80=AFPM Andrew Morton wrote: >> >> On Thu, 30 Jan 2025 16:18:04 -0800 "Vishal Moola (Oracle)" wrote: >> >> > Currently, users have to call vmap() or vmap_pfn() to map pages to >> > kernel virtual space. vmap() requires the page references, and >> > vmap_pfn() requires page pfns. If we have a file but no page reference= s, >> > we have to do extra work to map them. >> > >> > Create a function, vmap_file(), to map a specified range of a given >> > file to kernel virtual space. Also convert a user that benefits from >> > vmap_file(). >> > >> >> Seems like a pretty specialized thing. Have you identified any other >> potential users of vmap_file()? I couldn't see any. >> >> If drm is likely to remain the only user of this, perhaps we should >> leave the code down in drivers/gpu/drm for now? > > This function is generally useful for file-systems that use the pagecache= . > I simply chose to highlight the most obvious user that benefits from it (= and > so that the function is introduced with a user). > > I haven't identified any other specific users of vmap_file() myself. I kn= ow > Matthew has some other ideas for it; I've cc-ed him so he can chime in. Not much to add but just to confirm - yep, this seems like it might be useful as a part of the solution to the page cache perf issue[1] with ASI that I spoke about (briefly and chaotically) at the end of the LSF/MM/BPF session[0] on ASI this year. [0] https://lwn.net/Articles/1016013/ [1] https://lore.kernel.org/linux-mm/20250129144320.2675822-1-jackmanb@goog= le.com/ But, for the moment this is all still pretty vague stuff, not at all clear yet that this idea makes total sense. Hopefully I'll be able to follow up in a few weeks after I've made some time to stare at/prototype things.