linux-kernel - [PATCH] pstore/ram: Fix console ramoops to show the previous boot logs

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Date:   Thu, 17 Jan 2019 11:56:20 +0530
From:   Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>
To:     Kees Cook <keescook@...omium.org>,
        Joel Fernandes <joel@...lfernandes.org>,
        Anton Vorontsov <anton@...msg.org>,
        Colin Cross <ccross@...roid.com>,
        Tony Luck <tony.luck@...el.com>,
        Guenter Roeck <groeck@...omium.org>
Cc:     Rajendra Nayak <rnayak@...eaurora.org>,
        Vivek Gautam <vivek.gautam@...eaurora.org>,
        Sibi Sankar <sibis@...eaurora.org>,
        Stephen Boyd <sboyd@...nel.org>,
        Doug Anderson <dianders@...omium.org>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org,
        Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>
Subject: [PATCH] pstore/ram: Fix console ramoops to show the previous boot logs

commit b05c950698fe ("pstore/ram: Simplify ramoops_get_next_prz()
arguments") changed update assignment in getting next persistent
ram zone by adding a check for record type. But the check always
returns true since the record type is assigned 0. And this breaks
console ramoops by showing current console log instead of previous
log on warm reset and hard reset (actually hard reset should not
be showing any logs).

Fix this by having persistent ram zone type check instead of record
type check. Tested this on SDM845 MTP and dragonboard 410c.

Reproducing this issue is simple as below:

1. Trigger hard reset and mount pstore. Will see console-ramoops
   record in the mounted location which is the current log.

2. Trigger warm reset and mount pstore. Will see the current
   console-ramoops record instead of previous record.

Fixes: b05c950698fe ("pstore/ram: Simplify ramoops_get_next_prz() arguments")
Signed-off-by: Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>

---

I guess commit msg can be improved.
---
 fs/pstore/ram.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/fs/pstore/ram.c b/fs/pstore/ram.c
index 96f7d32cd184..441a44215456 100644
--- a/fs/pstore/ram.c
+++ b/fs/pstore/ram.c
@@ -128,7 +128,7 @@ ramoops_get_next_prz(struct persistent_ram_zone *przs[], int id,
 		     struct pstore_record *record)
 {
 	struct persistent_ram_zone *prz;
-	bool update = (record->type == PSTORE_TYPE_DMESG);
+	bool update;
 
 	/* Give up if we never existed or have hit the end. */
 	if (!przs)
@@ -138,6 +138,8 @@ ramoops_get_next_prz(struct persistent_ram_zone *przs[], int id,
 	if (!prz)
 		return NULL;
 
+	update = (prz->type == PSTORE_TYPE_DMESG);
+
 	/* Update old/shadowed buffer. */
 	if (update)
 		persistent_ram_save_old(prz);
-- 
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