pstore: replace spinlock_t by raw_spinlock_t

pstore_dump() is called when both preemption and local IRQ are disabled,
and a spinlock is obtained, which is problematic for the RT kernel because
in this configuration, spinlocks are sleep locks.

Replace the spinlock_t with raw_spinlock_t to avoid sleeping in atomic context.

Signed-off-by: Wen Yang <[e-mail]>
Cc: Kees Cook <[e-mail]>
Cc: Tony Luck <[e-mail]>
Cc: Guilherme G. Piccoli <[e-mail]>
Cc: [e-mail]
Cc: [e-mail]
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Kees Cook <[e-mail]>

fs/pstore/platform.c

···
 	why = kmsg_dump_reason_str(reason);
 
 	if (pstore_cannot_block_path(reason)) {
-		if (!spin_trylock_irqsave(&psinfo->buf_lock, flags)) {
+		if (!raw_spin_trylock_irqsave(&psinfo->buf_lock, flags)) {
 			pr_err("dump skipped in %s path because of concurrent dump\n",
 					in_nmi() ? "NMI" : why);
 			return;
 		}
 	} else {
-		spin_lock_irqsave(&psinfo->buf_lock, flags);
+		raw_spin_lock_irqsave(&psinfo->buf_lock, flags);
 	}
 
 	kmsg_dump_rewind(&iter);
···
 		total += record.size;
 		part++;
 	}
-	spin_unlock_irqrestore(&psinfo->buf_lock, flags);
+	raw_spin_unlock_irqrestore(&psinfo->buf_lock, flags);
 
 	if (saved_ret) {
 		pr_err_once("backend (%s) writing error (%d)\n", psinfo->name,
···
 		psi->write_user = pstore_write_user_compat;
 	psinfo = psi;
 	mutex_init(&psinfo->read_mutex);
-	spin_lock_init(&psinfo->buf_lock);
+	raw_spin_lock_init(&psinfo->buf_lock);
 
 	if (psi->flags & PSTORE_FLAGS_DMESG)
 		allocate_buf_for_compression();

include/linux/pstore.h

···
 	struct module	*owner;
 	const char	*name;
 
-	spinlock_t	buf_lock;
+	raw_spinlock_t	buf_lock;
 	char		*buf;
 	size_t		bufsize;