kexec: turn all kexec_mutex acquisitions into trylocks

stable inclusion
from stable-v5.10.178
commit d425f348211ffb387587dc65113852767240d023
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I8ALH3

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=d425f348211ffb387587dc65113852767240d023

--------------------------------

commit 7bb5da0d upstream.

Patch series "kexec, panic: Making crash_kexec() NMI safe", v4.

This patch (of 2):

Most acquistions of kexec_mutex are done via mutex_trylock() - those were
a direct "translation" from:

  8c5a1cf0 ("kexec: use a mutex for locking rather than xchg()")

there have however been two additions since then that use mutex_lock():
crash_get_memory_size() and crash_shrink_memory().

A later commit will replace said mutex with an atomic variable, and
locking operations will become atomic_cmpxchg().  Rather than having those
mutex_lock() become while (atomic_cmpxchg(&lock, 0, 1)), turn them into
trylocks that can return -EBUSY on acquisition failure.

This does halve the printable size of the crash kernel, but that's still
neighbouring 2G for 32bit kernels which should be ample enough.

Link: https://lkml.kernel.org/r/20220630223258.4144112-1-vschneid@redhat.com
Link: https://lkml.kernel.org/r/20220630223258.4144112-2-vschneid@redhat.com


Signed-off-by: Valentin Schneider <vschneid@redhat.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: "Eric W . Biederman" <ebiederm@xmission.com>
Cc: Juri Lelli <jlelli@redhat.com>
Cc: Luis Claudio R. Goncalves <lgoncalv@redhat.com>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Baoquan He <bhe@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Wen Yang <wenyang.linux@foxmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: sanglipeng <sanglipeng1@jd.com>