[PATCH] pstore/ram: fix for adding dumps to non-empty zone

[Nikolai Merinov <n.merinov@inango-systems.com>]

From: Aleksandr Yashkin <a.yashkin@inango-systems.com>

The circle buffer in ramoops zones has a problem for adding a new
oops dump to already an existing one.

The solution to this problem is to reset the circle buffer state before
writing a new oops dump.

Signed-off-by: Aleksandr Yashkin <a.yashkin@inango-systems.com>
Signed-off-by: Nikolay Merinov <n.merinov@inango-systems.com>
Signed-off-by: Ariel Gilman <a.gilman@inango-systems.com>

diff --git a/fs/pstore/ram.c b/fs/pstore/ram.c
index 8caff834f002..33fceadbf515 100644
--- a/fs/pstore/ram.c
+++ b/fs/pstore/ram.c
@@ -407,6 +407,13 @@ static int notrace ramoops_pstore_write(struct pstore_record *record)
 
 	prz = cxt->dprzs[cxt->dump_write_cnt];
 
+	/* Clean the buffer from old info.
+	 * `ramoops_read_kmsg_hdr' expects to find a header in the beginning of
+	 * buffer data, so we must to reset the buffer values, in order to
+	 * ensure that the header will be written to the beginning of the buffer
+	 */
+	persistent_ram_zap(prz);
+
 	/* Build header and append record contents. */
 	hlen = ramoops_write_kmsg_hdr(prz, record);
 	if (!hlen)
-- 
2.17.1