pstore: Don't warn if data is uncompressed and type is not PSTORE_TYPE_DMESG

commit 9abdcccc3d5f ("pstore: Extract common arguments into structure")
moved record decompression to function. decompress_record() gets
called without checking type and compressed flag. Warning will be
reported if data is uncompressed. Pstore type PSTORE_TYPE_PPC_OPAL,
PSTORE_TYPE_PPC_COMMON doesn't contain compressed data and warning get
printed part of dmesg.

Partial dmesg log:
[   35.848914] pstore: ignored compressed record type 6
[   35.848927] pstore: ignored compressed record type 8

Above warning should not get printed as it is known that data won't be
compressed for above type and it is valid condition.

This patch returns if data is not compressed and print warning only if
data is compressed and type is not PSTORE_TYPE_DMESG.

Reported-by: Anton Blanchard <anton@au1.ibm.com>
Signed-off-by: Ankit Kumar <ankit@linux.vnet.ibm.com>
Reviewed-by: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Fixes: 9abdcccc3d5f ("pstore: Extract common arguments into structure")
Cc: stable@vger.kernel.org

fs/pstore/platform.c

@@ -770,8 +770,11 @@ static void decompress_record(struct pstore_record *record)
 	int unzipped_len;
 	char *decompressed;
 
+	if (!record->compressed)
+		return;
+
 	/* Only PSTORE_TYPE_DMESG support compression. */
-	if (!record->compressed || record->type != PSTORE_TYPE_DMESG) {
+	if (record->type != PSTORE_TYPE_DMESG) {
 		pr_warn("ignored compressed record type %d\n", record->type);
 		return;
 	}