Messages in this thread Patch in this message | | | Date | Thu, 16 Feb 2023 13:01:50 +0300 | From | "Kirill A. Shutemov" <> | Subject | Re: [RFC PATCH 1/2] mm: restrictedmem: Allow userspace to specify mount_path for memfd_restricted |
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On Thu, Feb 16, 2023 at 12:41:16AM +0000, Ackerley Tng wrote: > By default, the backing shmem file for a restrictedmem fd is created > on shmem's kernel space mount. > > With this patch, an optional tmpfs mount can be specified, which will > be used as the mountpoint for backing the shmem file associated with a > restrictedmem fd. > > This change is modeled after how sys_open() can create an unnamed > temporary file in a given directory with O_TMPFILE. > > This will help restrictedmem fds inherit the properties of the > provided tmpfs mounts, for example, hugepage allocation hints, NUMA > binding hints, etc. > > Signed-off-by: Ackerley Tng <ackerleytng@google.com> > --- > include/linux/syscalls.h | 2 +- > include/uapi/linux/restrictedmem.h | 8 ++++ > mm/restrictedmem.c | 63 +++++++++++++++++++++++++++--- > 3 files changed, 66 insertions(+), 7 deletions(-) > create mode 100644 include/uapi/linux/restrictedmem.h > > diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h > index f9e9e0c820c5..4b8efe9a8680 100644 > --- a/include/linux/syscalls.h > +++ b/include/linux/syscalls.h > @@ -1056,7 +1056,7 @@ asmlinkage long sys_memfd_secret(unsigned int flags); > asmlinkage long sys_set_mempolicy_home_node(unsigned long start, unsigned long len, > unsigned long home_node, > unsigned long flags); > -asmlinkage long sys_memfd_restricted(unsigned int flags); > +asmlinkage long sys_memfd_restricted(unsigned int flags, const char __user *mount_path); > > /* > * Architecture-specific system calls
I'm not sure what the right practice now: do we provide string that contains mount path or fd that represents the filesystem (returned from fsmount(2) or open_tree(2)).
fd seems more flexible: it allows to specify unbind mounts.
-- Kiryl Shutsemau / Kirill A. Shutemov
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