[PATCH 0/6] Mount and superblock notifications [ver #5]

David Howells
2019-06-28T15:50:19Z

Here's a set of patches to adds VFS-related watches to the general
notification system to add sources of events for:

(1) Mount topology events, such as mounting, unmounting, mount expiry,
mount reconfiguration.

(2) Superblock events, such as R/W<->R/O changes, quota overrun and I/O
errors (not complete yet).

One of the reasons for this is so that we can remove the issue of processes
having to repeatedly and regularly scan /proc/mounts, which has proven to
be a system performance problem. To further aid this, the fsinfo() syscall
on which this patch series depends, provides a way to access superblock and
mount information in binary form without the need to parse /proc/mounts.

LSM hooks are included are provided that allow an LSM to rule on whether or
not a watch may be set. Each of these hooks takes a different "watched
object" parameter, so they're not really shareable. The LSM should use
current's credentials. [Wanted by SELinux & Smack]

Watches are created with:

watch_mount(AT_FDCWD, "/", 0, fd, 0x03);
watch_sb(AT_FDCWD, "/mnt", 0, fd, 0x04);

where in all three cases, fd indicates the queue and the number after is a
tag between 0 and 255.

Further things that could be considered:

(1) Adding global superblock event queue.

(2) Propagating watches to child superblock over automounts.

The patches can be found here also:

http://git.kernel.org/cgit/linux/kernel/git/dhowells/linux-fs.git/log/?h=notifications

Changes:

ver #5:

(*) The superblock watch and mount watch parts are split out into this set
from the core branch (notifications-core) as it depends on fsinfo().

David
---
David Howells (6):
security: Add hooks to rule on setting a superblock or mount watch
Adjust watch_queue documentation to mention mount and superblock watches.
vfs: Add a mount-notification facility
vfs: Add superblock notifications
fsinfo: Export superblock notification counter
Add sample notification program

Documentation/watch_queue.rst | 20 +++
arch/alpha/kernel/syscalls/syscall.tbl | 2
arch/arm/tools/syscall.tbl | 2
arch/arm64/include/asm/unistd.h | 2
arch/ia64/kernel/syscalls/syscall.tbl | 2
arch/m68k/kernel/syscalls/syscall.tbl | 2
arch/microblaze/kernel/syscalls/syscall.tbl | 2
arch/mips/kernel/syscalls/syscall_n32.tbl | 2
arch/mips/kernel/syscalls/syscall_n64.tbl | 2
arch/mips/kernel/syscalls/syscall_o32.tbl | 2
arch/parisc/kernel/syscalls/syscall.tbl | 2
arch/powerpc/kernel/syscalls/syscall.tbl | 2
arch/s390/kernel/syscalls/syscall.tbl | 2
arch/sh/kernel/syscalls/syscall.tbl | 2
arch/sparc/kernel/syscalls/syscall.tbl | 2
arch/x86/entry/syscalls/syscall_32.tbl | 2
arch/x86/entry/syscalls/syscall_64.tbl | 2
arch/xtensa/kernel/syscalls/syscall.tbl | 2
drivers/misc/Kconfig | 5 -
fs/Kconfig | 21 +++
fs/Makefile | 1
fs/fsinfo.c | 12 ++
fs/mount.h | 33 +++--
fs/mount_notify.c | 188 +++++++++++++++++++++++++++
fs/namespace.c | 16 ++
fs/super.c | 126 ++++++++++++++++++
include/linux/dcache.h | 1
include/linux/fs.h | 78 +++++++++++
include/linux/lsm_hooks.h | 16 ++
include/linux/security.h | 10 +
include/linux/syscalls.h | 4 +
include/uapi/asm-generic/unistd.h | 6 +
include/uapi/linux/fsinfo.h | 10 +
include/uapi/linux/watch_queue.h | 61 +++++++++
kernel/sys_ni.c | 2
samples/vfs/test-fsinfo.c | 13 ++
samples/watch_queue/watch_test.c | 76 +++++++++++
security/security.c | 10 +
38 files changed, 722 insertions(+), 21 deletions(-)
create mode 100644 fs/mount_notify.c