linux-stable.git/fs/namespace.c, branch v5.18

fs: unset MNT_WRITE_HOLD on failure

2022-04-21T15:57:37+00:00

After mnt_hold_writers() has been called we will always have set MNT_WRITE_HOLD
and consequently we always need to pair mnt_hold_writers() with
mnt_unhold_writers(). After the recent cleanup in [1] where Al switched from a
do-while to a for loop the cleanup currently fails to unset MNT_WRITE_HOLD for
the first mount that was changed. Fix this and make sure that the first mount
will be cleaned up and add some comments to make it more obvious.

Link: https://lore.kernel.org/lkml/0000000000007cc21d05dd0432b8@google.com
Link: https://lore.kernel.org/lkml/00000000000080e10e05dd043247@google.com
Link: https://lore.kernel.org/r/20220420131925.2464685-1-brauner@kernel.org
Fixes: e257039f0fc7 ("mount_setattr(): clean the control flow and calling conventions") [1]
Cc: Hillf Danton 
Cc: Christoph Hellwig 
Cc: Al Viro 
Reported-by: syzbot+10a16d1c43580983f6a2@syzkaller.appspotmail.com
Reported-by: syzbot+306090cfa3294f0bbfb3@syzkaller.appspotmail.com
Reviewed-by: Christoph Hellwig 
Signed-off-by: Christian Brauner (Microsoft)

Merge branch 'work.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

2022-04-02T02:57:03+00:00

Pull vfs updates from Al Viro:
 "Assorted bits and pieces"

* 'work.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  aio: drop needless assignment in aio_read()
  clean overflow checks in count_mounts() a bit
  seq_file: fix NULL pointer arithmetic warning
  uml/x86: use x86 load_unaligned_zeropad()
  asm/user.h: killed unused macros
  constify struct path argument of finish_automount()/do_add_mount()
  fs: Remove FIXME comment in generic_write_checks()

Merge tag 'fs.rt.v5.18' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux

2022-03-24T17:06:43+00:00

Pull mount attributes PREEMPT_RT update from Christian Brauner:
 "This contains Sebastian's fix to make changing mount
  attributes/getting write access compatible with CONFIG_PREEMPT_RT.

  The change only applies when users explicitly opt-in to real-time via
  CONFIG_PREEMPT_RT otherwise things are exactly as before. We've waited
  quite a long time with this to make sure folks could take a good look"

* tag 'fs.rt.v5.18' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux:
  fs/namespace: Boost the mount_lock.lock owner instead of spinning on PREEMPT_RT.

Merge tag 'fs.v5.18' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux

2022-03-24T16:55:15+00:00

Pull mount_setattr updates from Christian Brauner:
 "This contains a few more patches to massage the mount_setattr()
  codepaths and one minor fix to reuse a helper we added some time back.

  The final two patches do similar cleanups in different ways. One patch
  is mine and the other is Al's who was nice enough to give me a branch
  for it.

  Since his came in later and my branch had been sitting in -next for
  quite some time we just put his on top instead of swap them"

* tag 'fs.v5.18' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux:
  mount_setattr(): clean the control flow and calling conventions
  fs: clean up mount_setattr control flow
  fs: don't open-code mnt_hold_writers()
  fs: simplify check in mount_setattr_commit()
  fs: add mnt_allow_writers() and simplify mount_setattr_prepare()

mount: warn only once about timestamp range expiration

2022-03-22T22:57:01+00:00

Commit f8b92ba67c5d ("mount: Add mount warning for impending timestamp
expiry") introduced a mount warning regarding filesystem timestamp
limits, that is printed upon each writable mount or remount.

This can result in a lot of unnecessary messages in the kernel log in
setups where filesystems are being frequently remounted (or mounted
multiple times).

Avoid this by setting a superblock flag which indicates that the warning
has been emitted at least once for any particular mount, as suggested in
[1].

Link: https://lore.kernel.org/CAHk-=wim6VGnxQmjfK_tDg6fbHYKL4EFkmnTjVr9QnRqjDBAeA@mail.gmail.com/ [1]
Link: https://lkml.kernel.org/r/20220119202934.26495-1-ailiop@suse.com
Signed-off-by: Anthony Iliopoulos 
Reviewed-by: Christoph Hellwig 
Acked-by: Christian Brauner 
Reviewed-by: Darrick J. Wong 
Cc: Alexander Viro 
Cc: Deepa Dinamani 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mount_setattr(): clean the control flow and calling conventions

2022-03-15T23:17:13+00:00

separate the "cleanup" and "apply" codepaths (they have almost no overlap),
fold the "cleanup" into "prepare" (which eliminates the need of ->revert)
and make loops more idiomatic.

Signed-off-by: Al Viro

fs: clean up mount_setattr control flow

2022-02-14T07:37:40+00:00

Simplify the control flow of mount_setattr_{prepare,commit} so they
become easier to follow. We kept using both an integer error variable
that was passed by pointer as well as a pointer as an indicator for
whether or not we need to revert or commit the prepared changes.
Simplify this and just use the pointer. If we successfully changed
properties the revert pointer will be NULL and if we failed to change
properties it will indicate where we failed and thus need to stop
reverting.

Link: https://lore.kernel.org/r/20220203131411.3093040-8-brauner@kernel.org
Cc: Seth Forshee 
Cc: Christoph Hellwig 
Cc: Al Viro 
Cc: linux-fsdevel@vger.kernel.org
Reviewed-by: Christoph Hellwig 
Signed-off-by: Christian Brauner

fs: don't open-code mnt_hold_writers()

2022-02-14T07:37:40+00:00

Remove sb_prepare_remount_readonly()'s open-coded mnt_hold_writers()
implementation with the real helper we introduced in commit fbdc2f6c40f6
("fs: split out functions to hold writers").

Link: https://lore.kernel.org/r/20220203131411.3093040-7-brauner@kernel.org
Cc: Seth Forshee 
Cc: Christoph Hellwig 
Cc: Al Viro 
Cc: linux-fsdevel@vger.kernel.org
Reviewed-by: Christoph Hellwig 
Signed-off-by: Christian Brauner

fs: simplify check in mount_setattr_commit()

2022-02-14T07:37:40+00:00

In order to determine whether we need to call mnt_unhold_writers() in
mount_setattr_commit() we currently do not just check whether
MNT_WRITE_HOLD is set but also if a read-only mount was requested.

However, checking whether MNT_WRITE_HOLD is set is enough. Setting
MNT_WRITE_HOLD requires lock_mount_hash() to be held and it must be
unset before calling unlock_mount_hash(). This guarantees that if we see
MNT_WRITE_HOLD we know that we were the ones who set it earlier. We
don't need to care about why we set it. Plus, leaving this additional
read-only check in makes the code more confusing because it implies that
MNT_WRITE_HOLD could've been set by another thread when it really can't.
Remove it and update the associated comment.

Link: https://lore.kernel.org/r/20220203131411.3093040-6-brauner@kernel.org
Cc: Seth Forshee 
Cc: Christoph Hellwig 
Cc: Al Viro 
Cc: linux-fsdevel@vger.kernel.org
Reviewed-by: Christoph Hellwig 
Signed-off-by: Christian Brauner

fs: add mnt_allow_writers() and simplify mount_setattr_prepare()

2022-02-14T07:37:39+00:00

Add a tiny helper that lets us simplify the control-flow and can be used
in the next patch to avoid adding another condition open-coded into
mount_setattr_prepare(). Instead we can add it into the new helper.

Link: https://lore.kernel.org/r/20220203131411.3093040-5-brauner@kernel.org
Cc: Seth Forshee 
Cc: Christoph Hellwig 
Cc: Al Viro 
Cc: linux-fsdevel@vger.kernel.org
Reviewed-by: Christoph Hellwig 
Signed-off-by: Christian Brauner