vfs: syscall: Add fspick() to select a superblock for reconfiguration
authorDavid Howells <dhowells@redhat.com>
Thu, 1 Nov 2018 23:36:23 +0000 (23:36 +0000)
committerAl Viro <viro@zeniv.linux.org.uk>
Wed, 20 Mar 2019 22:49:06 +0000 (18:49 -0400)
commitcf3cba4a429be43e5527a3f78859b1bfd9ebc5fb
tree41f4c4a999e7e22644b0f3a220208519dc1f4ccd
parent93766fbd2696c2c4453dd8e1070977e9cd4e6b6d
vfs: syscall: Add fspick() to select a superblock for reconfiguration

Provide an fspick() system call that can be used to pick an existing
mountpoint into an fs_context which can thereafter be used to reconfigure a
superblock (equivalent of the superblock side of -o remount).

This looks like:

int fd = fspick(AT_FDCWD, "/mnt",
FSPICK_CLOEXEC | FSPICK_NO_AUTOMOUNT);
fsconfig(fd, FSCONFIG_SET_FLAG, "intr", NULL, 0);
fsconfig(fd, FSCONFIG_SET_FLAG, "noac", NULL, 0);
fsconfig(fd, FSCONFIG_CMD_RECONFIGURE, NULL, NULL, 0);

At the point of fspick being called, the file descriptor referring to the
filesystem context is in exactly the same state as the one that was created
by fsopen() after fsmount() has been successfully called.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: linux-api@vger.kernel.org
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
arch/x86/entry/syscalls/syscall_32.tbl
arch/x86/entry/syscalls/syscall_64.tbl
fs/fsopen.c
include/linux/syscalls.h
include/uapi/linux/mount.h