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Wong" To: Thomas =?iso-8859-1?Q?Wei=DFschuh?= Cc: Alexander Viro , Christian Brauner , Andrew Morton , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Willy Tarreau , Zhangjin Wu Subject: Re: [PATCH] mm: make MEMFD_CREATE into a selectable config option Message-ID: <20230630153236.GD11423@frogsfrogsfrogs> References: <20230630-config-memfd-v1-1-9acc3ae38b5a@weissschuh.net> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20230630-config-memfd-v1-1-9acc3ae38b5a@weissschuh.net> X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: B8A5F40033 X-Stat-Signature: b3rkrrha9xummc4qk9rmt94f9pxoz9iz X-HE-Tag: 1688139158-841540 X-HE-Meta: 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 0I9BAFhG +ygs06l4nxW242JFBJfLWPpRDVRiRQ6nOCJR5UnNQ7pOIDFlFTpaveHj8b0O17StExihFPYhtmbQ/OZq+vjDldHaUZEGIn3gujSKjc+/v6wzGui5xeJSt0W8Ze4+pnAMB2RE7qsml7YsjuPnKFF+mvS4RTgOmVA1KrPWn6gT8+0VR6r8m1M8W86oZ6+FevhPCIEFV4mEoJ7msxwoppgFcJMEgYpTXTvykrzT0II4JY8Upqn4irWq9cTA133vBSyoIb44J2/51CiUYXOq9h28uWuuqo0lfJfNd5vo/DfyC1w3px4aP0M1ACQjSQrqxiJjr41cJQ1V6+Lkae6uD8WPVRD45fn1m6A+AKEbBKHvqatfg8rsPPJvGs08zEfVd7TvejkjDMCLoNSxzJPo= 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: On Fri, Jun 30, 2023 at 11:08:53AM +0200, Thomas Weißschuh wrote: > The memfd_create() syscall, enabled by CONFIG_MEMFD_CREATE, is useful on > its own even when not required by CONFIG_TMPFS or CONFIG_HUGETLBFS. If you don't have tmpfs or hugetlbfs enabled, then what fs ends up backing the file returned by memfd_create()? ramfs? (Not an objection, I'm just curious...) --D > Split it into its own proper bool option that can be enabled by users. > > Move that option into mm/ where the code itself also lies. > Also add "select" statements to CONFIG_TMPFS and CONFIG_HUGETLBFS so > they automatically enable CONFIG_MEMFD_CREATE as before. > > Signed-off-by: Thomas Weißschuh > --- > fs/Kconfig | 5 ++--- > mm/Kconfig | 3 +++ > 2 files changed, 5 insertions(+), 3 deletions(-) > > diff --git a/fs/Kconfig b/fs/Kconfig > index 18d034ec7953..19975b104bc3 100644 > --- a/fs/Kconfig > +++ b/fs/Kconfig > @@ -169,6 +169,7 @@ source "fs/sysfs/Kconfig" > config TMPFS > bool "Tmpfs virtual memory file system support (former shm fs)" > depends on SHMEM > + select MEMFD_CREATE > help > Tmpfs is a file system which keeps all files in virtual memory. > > @@ -240,6 +241,7 @@ config HUGETLBFS > bool "HugeTLB file system support" > depends on X86 || IA64 || SPARC64 || ARCH_SUPPORTS_HUGETLBFS || BROKEN > depends on (SYSFS || SYSCTL) > + select MEMFD_CREATE > help > hugetlbfs is a filesystem backing for HugeTLB pages, based on > ramfs. For architectures that support it, say Y here and read > @@ -264,9 +266,6 @@ config HUGETLB_PAGE_OPTIMIZE_VMEMMAP_DEFAULT_ON > enable HVO by default. It can be disabled via hugetlb_free_vmemmap=off > (boot command line) or hugetlb_optimize_vmemmap (sysctl). > > -config MEMFD_CREATE > - def_bool TMPFS || HUGETLBFS > - > config ARCH_HAS_GIGANTIC_PAGE > bool > > diff --git a/mm/Kconfig b/mm/Kconfig > index 09130434e30d..22acffd9009d 100644 > --- a/mm/Kconfig > +++ b/mm/Kconfig > @@ -1144,6 +1144,9 @@ config KMAP_LOCAL_NON_LINEAR_PTE_ARRAY > config IO_MAPPING > bool > > +config MEMFD_CREATE > + bool "Enable memfd_create() system call" if EXPERT > + > config SECRETMEM > default y > bool "Enable memfd_secret() system call" if EXPERT > > --- > base-commit: e55e5df193d247a38a5e1ac65a5316a0adcc22fa > change-id: 20230629-config-memfd-be6af03b7dca > > Best regards, > -- > Thomas Weißschuh >