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(c-67-164-59-41.hsd1.ca.comcast.net. [67.164.59.41]) by smtp.googlemail.com with ESMTPSA id 98e67ed59e1d1-30516d55fbasm2407137a91.15.2025.03.28.14.15.35 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 28 Mar 2025 14:15:36 -0700 (PDT) From: "Vishal Moola (Oracle)" To: linux-mm@kvack.org Cc: Andrew Morton , Brendan Jackman , Huan Yang , linux-kernel@vger.kernel.org, "Vishal Moola (Oracle)" Subject: [RFC PATCH v2 0/1] Introduce vmap_file() Date: Fri, 28 Mar 2025 14:13:48 -0700 Message-ID: <20250328211349.845857-1-vishal.moola@gmail.com> X-Mailer: git-send-email 2.48.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Currently, users have to call vmap() or vmap_pfn() to map pages to kernel virtual space. vmap_pfn() is for special pages (i.e. pfns without struct page). vmap() handles normal pages. With large folios, we may want to map ranges that only span part of a folio (i.e. mapping half of a 2Mb folio). vmap_file() will allow us to do so. Create a function, vmap_file(), to map a specified range of a given file to kernel virtual space. vmap_file() is an in-kernel equivalent to mmap(), and can be useful for filesystems. --- v2: - Reword cover letter to provide a clearer overview of the current vmalloc APIs, and usefulness of vmap_file() - EXPORT_SYMBOL_GPL() instead of EXPORT_SYMBOL() - Provide support to partially map file folios - Demote this to RFC while we look for users -- I don't have a user for this function right now, but it will be useful as users start converting to using large folios. I'm just putting it out here for anyone that may find a use for it. This seems like the sensible way to implement it, but I'm open to tweaking the functions semantics. I've Cc-ed a couple people that mentioned they might be interested in using it. Vishal Moola (Oracle) (1): mm/vmalloc: Introduce vmap_file() include/linux/vmalloc.h | 2 + mm/vmalloc.c | 113 ++++++++++++++++++++++++++++++++++++++++ 2 files changed, 115 insertions(+) -- 2.48.1