[PATCH v1 2/2] mtd: mtdoops: panic caused mtdoops to call mtd erase function immediately

[Ray Zhang]

The panic function disables the local interrupts, preemption, and all
other processors. When the invoked mtdoops needs to erase a used page,
calling schedule_work() to do it will not work. Instead, just call mtd
erase function immediately.

Tested:
~# echo c > /proc/sysrq-trigger
[  171.654759] sysrq: Trigger a crash
[  171.658325] Kernel panic - not syncing: sysrq triggered crash
......
[  172.406423] mtdoops: not ready 34, 35 (erase immediately)
[  172.432285] mtdoops: ready 34, 35
[  172.435633] Rebooting in 10 seconds..

Signed-off-by: Ray Zhang <sgzhang at google.com>
---
 drivers/mtd/mtdoops.c | 66 ++++++++++++++++++++++++++-----------------
 1 file changed, 40 insertions(+), 26 deletions(-)

diff --git a/drivers/mtd/mtdoops.c b/drivers/mtd/mtdoops.c
index 84b21be347f6..73c6a55eb391 100644
--- a/drivers/mtd/mtdoops.c
+++ b/drivers/mtd/mtdoops.c
@@ -106,29 +106,8 @@ static int mtdoops_erase_block(struct mtdoops_context *cxt, int offset)
 	return 0;
 }
 
-static void mtdoops_inc_counter(struct mtdoops_context *cxt)
+static void mtdoops_erase(struct mtdoops_context *cxt)
 {
-	cxt->nextpage++;
-	if (cxt->nextpage >= cxt->oops_pages)
-		cxt->nextpage = 0;
-	cxt->nextcount++;
-	if (cxt->nextcount == 0xffffffff)
-		cxt->nextcount = 0;
-
-	if (page_is_used(cxt, cxt->nextpage)) {
-		schedule_work(&cxt->work_erase);
-		return;
-	}
-
-	pr_debug("mtdoops: ready %d, %d (no erase)\n",
-		 cxt->nextpage, cxt->nextcount);
-}
-
-/* Scheduled work - when we can't proceed without erasing a block */
-static void mtdoops_workfunc_erase(struct work_struct *work)
-{
-	struct mtdoops_context *cxt =
-			container_of(work, struct mtdoops_context, work_erase);
 	struct mtd_info *mtd = cxt->mtd;
 	int i = 0, j, ret, mod;
 
@@ -166,8 +145,8 @@ static void mtdoops_workfunc_erase(struct work_struct *work)
 		ret = mtdoops_erase_block(cxt, cxt->nextpage * record_size);
 
 	if (ret >= 0) {
-		pr_debug("mtdoops: ready %d, %d\n",
-			 cxt->nextpage, cxt->nextcount);
+		pr_notice("mtdoops: ready %d, %d\n",
+			  cxt->nextpage, cxt->nextcount);
 		return;
 	}
 
@@ -181,6 +160,41 @@ static void mtdoops_workfunc_erase(struct work_struct *work)
 	goto badblock;
 }
 
+/* Scheduled work - when we can't proceed without erasing a block */
+static void mtdoops_workfunc_erase(struct work_struct *work)
+{
+	struct mtdoops_context *cxt =
+			container_of(work, struct mtdoops_context, work_erase);
+
+	mtdoops_erase(cxt);
+}
+
+static void mtdoops_inc_counter(struct mtdoops_context *cxt, int panic)
+{
+	cxt->nextpage++;
+	if (cxt->nextpage >= cxt->oops_pages)
+		cxt->nextpage = 0;
+	cxt->nextcount++;
+	if (cxt->nextcount == 0xffffffff)
+		cxt->nextcount = 0;
+
+	if (page_is_used(cxt, cxt->nextpage)) {
+		pr_notice("mtdoops: not ready %d, %d (erase %s)\n",
+			  cxt->nextpage, cxt->nextcount,
+			  panic ? "immediately" : "scheduled");
+		if (panic) {
+			/* In case of panic, erase immediately */
+			mtdoops_erase(cxt);
+		} else {
+			/* Otherwise, schedule work to erase it "nicely" */
+			schedule_work(&cxt->work_erase);
+		}
+	} else {
+		pr_notice("mtdoops: ready %d, %d (no erase)\n",
+			  cxt->nextpage, cxt->nextcount);
+	}
+}
+
 static void mtdoops_write(struct mtdoops_context *cxt, int panic)
 {
 	struct mtd_info *mtd = cxt->mtd;
@@ -214,7 +228,7 @@ static void mtdoops_write(struct mtdoops_context *cxt, int panic)
 	mark_page_used(cxt, cxt->nextpage);
 	memset(cxt->oops_buf, 0xff, record_size);
 
-	mtdoops_inc_counter(cxt);
+	mtdoops_inc_counter(cxt, panic);
 out:
 	clear_bit(0, &cxt->oops_buf_busy);
 }
@@ -279,7 +293,7 @@ static void find_next_position(struct mtdoops_context *cxt)
 		cxt->nextcount = maxcount;
 	}
 
-	mtdoops_inc_counter(cxt);
+	mtdoops_inc_counter(cxt, 0);
 }
 
 static void mtdoops_do_dump(struct kmsg_dumper *dumper,
-- 
2.37.3.998.g577e59143f-goog