s390/time: use stck clock fast for do_account_vtime

The last high frequency call site of the STCK instruction is
do_account_vtime. Replace it with the faster STCKF instruction.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
s390/vdso: fix stack corruption

The kernel provided vdso functions do not get a stack frame from the
calling function and therefore may not change the stack contents, unless
they allocate space on their own.

This problem was exposed with 070b7be633dc "s390/vdso: replace stck with
stcke" which writes 16 bytes instead of 8 bytes into the stack frame. These
additional 8 bytes however were indeed used by the caller (glibc) to save
data and therefore this data was corrupted by the vdso code.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
s390: update default configuration

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
s390/ftrace: add ftrace_graph_is_dead() check

Add an ftrace_graph_is_dead() check to prepare_ftrace_return() in order to
detect an internal ftrace graph error. This allows to prevent further ftrace
graph handling and hopefully keeps the kernel alive.

This patch is the same like for all other architectures.
For unkown reasons s390 was left out.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
ovl: don't poison cursor

ovl_cache_put() can be called from ovl_dir_reset() if the cache needs to be
rebuilt.  We did list_del() on the cursor, which results in an Oops on the
poisoned pointer in ovl_seek_cursor().

Reported-by: Jordi Pujol Palomer <jordipujolp@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Tested-by: Jordi Pujol Palomer <jordipujolp@gmail.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux

Pull s390 update from Martin Schwidefsky:
 "One small improvement for the cputime accounting, two bug fixes and an
  update for the default configuration files"

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux:
  s390/ftrace: add ftrace_graph_is_dead() check
  s390: update default configuration
  s390/vdso: fix stack corruption
  s390/time: use stck clock fast for do_account_vtime
Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

Pull vfs fix from Al Viro:
 "Another overlayfs fix"

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  ovl: don't poison cursor