[RFC v10 2/4] pstore/blk: add blkoops for pstore_blk

[liaoweixiong]

blkoops is a sample for pstore/blk. It can only record oops, excluding
panics as no read/write apis for panic registered. It support settings
on Kconfg/module parameters. It can record oops log even power failure
if "PSTORE_BLKOOPS_BLKDEV" on Kconfig or "blkdev" on module parameter
is valid. Otherwise, it can only record data to ram buffer, which will
be dropped when reboot.

Signed-off-by: liaoweixiong <liaoweixiong@xxxxxxxxxxxxxxxxx>
---
 MAINTAINERS                |   2 +-
 fs/pstore/Kconfig          | 114 ++++++++++++++++++++++++++
 fs/pstore/Makefile         |   2 +
 fs/pstore/blkoops.c        | 198 +++++++++++++++++++++++++++++++++++++++++++++
 include/linux/pstore_blk.h |  14 +++-
 5 files changed, 325 insertions(+), 5 deletions(-)
 create mode 100644 fs/pstore/blkoops.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 51029a4..4e9242a 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -12318,7 +12318,7 @@ F:	drivers/firmware/efi/efi-pstore.c
 F:	drivers/acpi/apei/erst.c
 F:	Documentation/admin-guide/ramoops.rst
 F:	Documentation/devicetree/bindings/reserved-memory/ramoops.txt
-K:	\b(pstore|ramoops)
+K:	\b(pstore|ramoops|blkoops)
 
 PTP HARDWARE CLOCK SUPPORT
 M:	Richard Cochran <richardcochran@xxxxxxxxx>
diff --git a/fs/pstore/Kconfig b/fs/pstore/Kconfig
index defcb75..7dfe00b 100644
--- a/fs/pstore/Kconfig
+++ b/fs/pstore/Kconfig
@@ -160,3 +160,117 @@ config PSTORE_BLK
 	help
 	  This enables panic and oops message to be logged to a block dev
 	  where it can be read back at some later point.
+
+config PSTORE_BLKOOPS
+	tristate "pstore block with oops logger"
+	depends on PSTORE_BLK
+	help
+	  This is a sample for pstore block with oops logger.
+
+	  It CANNOT record panic log as no read/write apis for panic registered.
+
+	  It CAN record oops log even power failure if
+	  "PSTORE_BLKOOPS_BLKDEV" on Kconfig or "block-device" on dts or
+	  "blkdev" on module parameter is valid.
+
+	  Otherwise, it can only record data to ram buffer, which will be
+	  dropped when reboot.
+
+	  NOTE that, there are three ways to set parameters of blkoops and
+	  prioritize according to configuration flexibility. That is
+	  Kconfig < device tree < module parameters. It means that the value can
+	  be overwritten by higher priority settings.
+	  1. Kconfig
+	     It	just sets a default value.
+	  2. device tree
+	     It is set on device tree, which will overwrites value from Kconfig,
+	     but can also be overwritten by module parameters.
+	  3. module parameters
+	     It is the first priority. Take care of that blkoops will take lower
+	     priority settings if higher priority one do not set.
+
+config PSTORE_BLKOOPS_DMESG_SIZE
+	int "dmesg size in kbytes for blkoops"
+	depends on PSTORE_BLKOOPS
+	default 64
+	help
+	  This just sets size of dmesg (dmesg_size) for pstore/blk. The value
+	  must be a multiple of 4096.
+
+	  NOTE that, there are three ways to set parameters of blkoops and
+	  prioritize according to configuration flexibility. That is
+	  Kconfig < device tree < module parameters. It means that the value can
+	  be overwritten by higher priority settings.
+	  1. Kconfig
+	     It	just sets a default value.
+	  2. device tree
+	     It is set on device tree, which will overwrites value from Kconfig,
+	     but can also be overwritten by module parameters.
+	  3. module parameters
+	     It is the first priority. Take care of that blkoops will take lower
+	     priority settings if higher priority one do not set.
+
+config PSTORE_BLKOOPS_TOTAL_SIZE
+	int "total size in kbytes for blkoops"
+	depends on PSTORE_BLKOOPS
+	default 0
+	help
+	  The total size in kbytes pstore/blk can use. It must be less than or
+	  equal to size of block device if @blkdev valid. If @total_size is zero
+	  with @blkdev, @total_size will be set to equal to size of @blkdev.
+	  The value must be a multiple of 4096.
+
+	  NOTE that, there are three ways to set parameters of blkoops and
+	  prioritize according to configuration flexibility. That is
+	  Kconfig < device tree < module parameters. It means that the value can
+	  be overwritten by higher priority settings.
+	  1. Kconfig
+	     It	just sets a default value.
+	  2. device tree
+	     It is set on device tree, which will overwrites value from Kconfig,
+	     but can also be overwritten by module parameters.
+	  3. module parameters
+	     It is the first priority. Take care of that blkoops will take lower
+	     priority settings if higher priority one do not set.
+
+config PSTORE_BLKOOPS_BLKDEV
+	string "block device for blkoops"
+	depends on PSTORE_BLKOOPS
+	default ""
+	help
+	  This just sets block device (blkdev) for pstore/blk. Pstore/blk
+	  will record data to this block device to avoid losing data due to
+	  power failure. So, If it is not set, pstore/blk will drop all data
+	  when reboot.
+
+	  It accpet the following variants:
+	  1) <hex_major><hex_minor> device number in hexadecimal represents
+	     itself no leading 0x, for example b302.
+	  2) /dev/<disk_name> represents the device number of disk
+	  3) /dev/<disk_name><decimal> represents the device number
+	     of partition - device number of disk plus the partition number
+	  4) /dev/<disk_name>p<decimal> - same as the above, that form is
+	     used when disk name of partitioned disk ends on a digit.
+	  5) PARTUUID=00112233-4455-6677-8899-AABBCCDDEEFF representing the
+	     unique id of a partition if the partition table provides it.
+	     The UUID may be either an EFI/GPT UUID, or refer to an MSDOS
+	     partition using the format SSSSSSSS-PP, where SSSSSSSS is a zero-
+	     filled hex representation of the 32-bit "NT disk signature", and PP
+	     is a zero-filled hex representation of the 1-based partition number.
+	  6) PARTUUID=<UUID>/PARTNROFF=<int> to select a partition in relation
+	     to a partition with a known unique id.
+	  7) <major>:<minor> major and minor number of the device separated by
+	     a colon.
+
+	  NOTE that, there are three ways to set parameters of blkoops and
+	  prioritize according to configuration flexibility. That is
+	  Kconfig < device tree < module parameters. It means that the value can
+	  be overwritten by higher priority settings.
+	  1. Kconfig
+	     It	just sets a default value.
+	  2. device tree
+	     It is set on device tree, which will overwrites value from Kconfig,
+	     but can also be overwritten by module parameters.
+	  3. module parameters
+	     It is the first priority. Take care of that blkoops will take lower
+	     priority settings if higher priority one do not set.
diff --git a/fs/pstore/Makefile b/fs/pstore/Makefile
index 0ee2fc8..24b3d48 100644
--- a/fs/pstore/Makefile
+++ b/fs/pstore/Makefile
@@ -15,3 +15,5 @@ obj-$(CONFIG_PSTORE_RAM)	+= ramoops.o
 
 obj-$(CONFIG_PSTORE_BLK) += pstore_blk.o
 pstore_blk-y += blkzone.o
+
+obj-$(CONFIG_PSTORE_BLKOOPS) += blkoops.o
diff --git a/fs/pstore/blkoops.c b/fs/pstore/blkoops.c
new file mode 100644
index 0000000..22c0c84
--- /dev/null
+++ b/fs/pstore/blkoops.c
@@ -0,0 +1,198 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ *
+ * blkoops.c: Block device Oops logger
+ *
+ * Copyright (C) 2019 liaoweixiong <liaoweixiong@xxxxxxxxxxxxxxxxxx>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ */
+#define MODNAME "blkoops"
+#define pr_fmt(fmt) MODNAME ": " fmt
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/string.h>
+#include <linux/of.h>
+#include <linux/of_address.h>
+#include <linux/platform_device.h>
+#include <linux/pstore_blk.h>
+
+static long dmesg_size = -1;
+module_param(dmesg_size, long, 0400);
+MODULE_PARM_DESC(dmesg_size, "demsg size in kbytes");
+
+static long total_size = -1;
+module_param(total_size, long, 0400);
+MODULE_PARM_DESC(total_size, "total size in kbytes");
+
+#define BLKDEV_INVALID "INVALID"
+static char blkdev[80] = {BLKDEV_INVALID};
+module_param_string(blkdev, blkdev, 80, 0400);
+MODULE_PARM_DESC(blkdev, "the block device for general read/write");
+
+struct blkz_info blkz_info = {
+	.owner = THIS_MODULE,
+	.name = "blkoops",
+	.dump_oops = true,
+};
+
+struct blkoops_info {
+	unsigned long dmesg_size;
+	unsigned long total_size;
+	const char *blkdev;
+};
+struct blkoops_info blkoops_info = {
+	.dmesg_size = CONFIG_PSTORE_BLKOOPS_DMESG_SIZE * 1024,
+	.total_size = CONFIG_PSTORE_BLKOOPS_TOTAL_SIZE * 1024,
+	.blkdev = CONFIG_PSTORE_BLKOOPS_BLKDEV,
+};
+
+static struct platform_device *dummy;
+DEFINE_SPINLOCK(modify_blkzinfo);
+
+/**
+ * Block driver use this function to add panic read/write apis to blkoops.
+ * By this, block driver can do the least work that just provides panic ops.
+ */
+int blkoops_add_panic_ops(blkz_read_op panic_read, blkz_write_op panic_write)
+{
+	struct blkz_info *info = &blkz_info;
+
+	spin_lock(&modify_blkzinfo);
+	if (info->panic_read || info->panic_write) {
+		spin_unlock(&modify_blkzinfo);
+		return -EBUSY;
+	}
+
+	info->panic_read = panic_read;
+	info->panic_write = panic_write;
+
+	spin_unlock(&modify_blkzinfo);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(blkoops_add_panic_ops);
+
+static int blkoops_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct blkoops_info *info = dev->platform_data;
+
+	if (info->blkdev[0] == '\0' || !strcmp(info->blkdev, BLKDEV_INVALID)) {
+		pr_info("no block device, use ram buffer only\n");
+	} else {
+		pr_debug("block device: %s\n", info->blkdev);
+		blkz_info.blkdev = info->blkdev;
+	}
+
+#define check_size(name, size) {					\
+		if (info->name & (size - 1)) {				\
+			pr_err(#name " must be a multiple of %d\n",	\
+					(size));			\
+			return -EINVAL;					\
+		}							\
+		blkz_info.name = info->name;				\
+	}
+
+	check_size(total_size, 4096);
+	check_size(dmesg_size, 4096);
+
+#undef check_size
+
+	/*
+	 * Update the module parameter variables as well so they are visible
+	 * through /sys/module/blkoops/parameters/
+	 */
+	dmesg_size = blkz_info.dmesg_size;
+	total_size = blkz_info.total_size;
+	if (blkz_info.blkdev)
+		strncpy(blkdev, blkz_info.blkdev, 80 - 1);
+	else
+		blkdev[0] = '\0';
+	return blkz_register(&blkz_info);
+}
+
+static int blkoops_remove(struct platform_device *pdev)
+{
+	blkz_unregister(&blkz_info);
+	return 0;
+}
+
+static const struct of_device_id dt_match[] = {
+	{ .compatible = MODNAME},
+	{}
+};
+
+static struct platform_driver blkoops_driver = {
+	.probe		= blkoops_probe,
+	.remove		= blkoops_remove,
+	.driver		= {
+		.name		= MODNAME,
+		.of_match_table	= dt_match,
+	},
+};
+
+void blkoops_register_dummy(void)
+{
+	struct blkoops_info *info = &blkoops_info;
+
+	/*
+	 * Prepare a dummy platform data structure to carry the module
+	 * parameters or kconfig value.
+	 */
+	if (total_size > 0 || strcmp(blkdev, BLKDEV_INVALID)) {
+		pr_info("using module parameters\n");
+		if (total_size >= 0)
+			info->total_size = (unsigned long)total_size * 1024;
+		if (strcmp(blkdev, BLKDEV_INVALID))
+			info->blkdev = (const char *)blkdev;
+		if (dmesg_size >= 0)
+			info->dmesg_size = (unsigned long)dmesg_size * 1024;
+	} else if (info->total_size > 0 || strlen(info->blkdev)) {
+		pr_info("using kconfig value\n");
+	} else {
+		return;
+	}
+
+	dummy = platform_device_register_data(NULL, MODNAME, -1, info,
+			sizeof(*info));
+	if (IS_ERR(dummy)) {
+		pr_err("could not create platform device: %ld\n",
+			PTR_ERR(dummy));
+		dummy = NULL;
+	}
+}
+
+static int __init blkoops_init(void)
+{
+	int ret;
+
+	blkoops_register_dummy();
+	ret = platform_driver_register(&blkoops_driver);
+	if (ret != 0) {
+		platform_device_unregister(dummy);
+		dummy = NULL;
+	}
+	return ret;
+}
+late_initcall(blkoops_init);
+
+static void __exit blkoops_exit(void)
+{
+	platform_driver_unregister(&blkoops_driver);
+	platform_device_unregister(dummy);
+	dummy = NULL;
+}
+module_exit(blkoops_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("liaoweixiong <liaoweixiong@xxxxxxxxxxxxxxxxx>");
+MODULE_DESCRIPTION("Sample for Pstore BLK with Oops logger");
diff --git a/include/linux/pstore_blk.h b/include/linux/pstore_blk.h
index 4f239f0..2d2ff97 100644
--- a/include/linux/pstore_blk.h
+++ b/include/linux/pstore_blk.h
@@ -60,6 +60,8 @@
  * @panic_write:
  *	the write operation only used for panic.
  */
+typedef ssize_t (*blkz_read_op)(char *, size_t, loff_t);
+typedef ssize_t (*blkz_write_op)(const char *, size_t, loff_t);
 struct blkz_info {
 	struct module *owner;
 	const char *name;
@@ -68,13 +70,17 @@ struct blkz_info {
 	unsigned long total_size;
 	unsigned long dmesg_size;
 	int dump_oops;
-	ssize_t (*read)(char *buf, size_t bytes, loff_t pos);
-	ssize_t (*write)(const char *buf, size_t bytes, loff_t pos);
-	ssize_t (*panic_read)(char *buf, size_t bytes, loff_t pos);
-	ssize_t (*panic_write)(const char *buf, size_t bytes, loff_t pos);
+	blkz_read_op read;
+	blkz_write_op write;
+	blkz_read_op panic_read;
+	blkz_write_op panic_write;
 };
 
 extern int blkz_register(struct blkz_info *info);
 extern void blkz_unregister(struct blkz_info *info);
 
+#if IS_ENABLED(CONFIG_PSTORE_BLKOOPS)
+extern int blkoops_add_panic_ops(blkz_read_op, blkz_write_op);
+#endif
+
 #endif
-- 
1.9.1