Replace the old ns->bacct only with NULL and only if it still points
to acct. And assign the new value to it *before* calling acct_kill()
in acct_on(). That way we don't need to pass the new acct to acct_kill().
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
If ACCT_VERSION is not defined to 3, below warning appears:
CC kernel/acct.o
kernel/acct.c: In function `do_acct_process':
kernel/acct.c:475:24: warning: unused variable `ns' [-Wunused-variable]
[akpm@linux-foundation.org: retain the local for code size improvements
Signed-off-by: Ying Xue <ying.xue@windriver.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Rather than playing silly buggers with vfsmount refcounts, just have
acct_on() ask fs/namespace.c for internal clone of file->f_path.mnt
and replace it with said clone. Then attach the pin to original
vfsmount. Voila - the clone will be alive until the file gets closed,
making sure that underlying superblock remains active, etc., and
we can drop the original vfsmount, so that it's not kept busy.
If the file lives until the final mntput of the original vfsmount,
we'll notice that there's an fs_pin (one in bsd_acct_struct that
holds that file) and mnt_pin_kill() will take it out. Since
->kill() is synchronous, we won't proceed past that point until
these files are closed (and private clones of our vfsmount are
gone), so we get the same ordering warranties we used to get.
mnt_pin()/mnt_unpin()/->mnt_pinned is gone now, and good riddance -
it never became usable outside of kernel/acct.c (and racy wrt
umount even there).
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Add a new field to fs_pin - kill(pin). That's what umount and r/o remount
will be calling for all pins attached to vfsmount and superblock resp.
Called after bumping the refcount, so it won't go away under us. Dropping
the refcount is responsibility of the instance. All generic stuff moved to
fs/fs_pin.c; the next step will rip all the knowledge of kernel/acct.c from
fs/super.c and fs/namespace.c. After that - death to mnt_pin(); it was
intended to be usable as generic mechanism for code that wants to attach
objects to vfsmount, so that they would not make the sucker busy and
would get killed on umount. Never got it right; it remained acct.c-specific
all along. Now it's very close to being killable.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
pull generic parts into struct fs_pin. Eventually we want those
to replace mnt_pin()/mnt_unpin() mess; that stuff will move to
fs/*.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* make acct->count atomic and acct freeing - rcu-delayed.
* instead of grabbing acct_lock around the places where we take a reference,
do that under rcu_read_lock() with atomic_long_inc_not_zero().
* have the new acct locked before making ns->bacct point to it
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Put these suckers on per-vfsmount and per-superblock lists instead.
Note: right now it's still acct_lock for everything, but that's
going to change.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
a) file can't be NULL
b) file can't be changed under us
c) all writes are serialized by acct->lock; no need to mess with
spinlock there.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Do not reuse bsd_acct_struct after closing the damn thing.
Structure lifetime is controlled by refcount now. We also
have a mutex in there, held over closing and writing (the
file is O_APPEND, so we are not losing any concurrency).
As the result, we do not need to bother with get_file()/fput()
on log write anymore. Moreover, do_acct_process() only needs
acct itself; file and pidns are picked from it.
Killed instances are distinguished by having NULL ->ns.
Refcount is protected by acct_lock; anybody taking the
mutex needs to grab a reference first.
The things will get a lot simpler in the next commits - this
is just the minimal chunk switching to the new lifetime rules.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
There was an amusing bogosity in ac_rw calculation - it tried to
do encode_comp_t(encode_comp_t(0) / 1024). Seeing that comp_t is
a 3-bit exponent + 13-bit mantissa... it's a good thing that 0 is
represented by all-bits-clear.
The history of that one is interesting - it was introduced in
2.1.68pre1, when acct.c had been reworked and moved to separate
file. Two months later (2.1.86) somebody has noticed that the
sucker won't compile - there was no task_struct::io_usage.
At which point the ac_io calculation had changed from
encode_comp_t(current->io_usage) to encode_comp_t(0) and the
bug in the next line (absolutely real back then, had it ever
managed to compile) become a harmless bogosity. Looks like
nobody has ever noticed until now.
Anyway, let's bury that idiocy now that it got noticed. 17 years
is long enough...
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
