Re: [PATCH v1 11/11] mtd: new support oops logger based on pstore/blk

[Miquel Raynal <miquel.raynal@bootlin.com>]

Hi WeiXiong,

WeiXiong Liao <liaoweixiong@allwinnertech.com> wrote on Mon, 20 Jan
2020 09:03:53 +0800:

> It's the last one of a series of patches for adaptive to MTD device.
> 
> The mtdpstore is similar to mtdoops but more powerful. It bases on
> pstore/blk, aims to store panic and oops log to a flash partition,

                                           logs?

> where it can be read back as files after mounting pstore filesystem.
> 
> The pstore/blk and blkoops, a wrapper for pstore/blk, are designed for
> block device at the very beginning, but now, compatible to not only
> block device. After this series of patches, pstore/blk can also work
> for MTD device. To make it work, 'blkdev' on kconfig or module
> parameter of blkoops should be set as mtd device name or mtd number.
> See more about pstore/blk and blkoops on:
>     Documentation/admin-guide/pstore-block.rst
> 
> Why do we need mtdpstore?
> 1. repetitive jobs between pstore and mtdoops
>    Both of pstore and mtdoops do the same jobs that store panic/oops log.
>    They have much similar logic that register to kmsg dumper and store
>    log to several chunks one by one.
> 2. do what a driver should do
>    To me, a driver should provide methods instead of policies. What MTD
>    should do is to provide read/write/erase operations, geting rid of codes
>    about chunk management, kmsg dumper and configuration.
> 3. enhanced feature
>    Not only store log, but also show it as files.
>    Not only log, but also trigger time and trigger count.
>    Not only panic/oops log, but also log recorder for pmsg, console and
>    ftrace in the future.
> 
> Signed-off-by: WeiXiong Liao <liaoweixiong@allwinnertech.com>
> Reported-by: kbuild test robot <lkp@intel.com>

I don't thing the test robot has a meaning here.

> ---
>  drivers/mtd/Kconfig     |  10 +
>  drivers/mtd/Makefile    |   1 +
>  drivers/mtd/mtdpstore.c | 530 ++++++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 541 insertions(+)
>  create mode 100644 drivers/mtd/mtdpstore.c
> 
> diff --git a/drivers/mtd/Kconfig b/drivers/mtd/Kconfig
> index 42d401ea60ee..a6e59495a738 100644
> --- a/drivers/mtd/Kconfig
> +++ b/drivers/mtd/Kconfig
> @@ -170,6 +170,16 @@ config MTD_OOPS
>  	  buffer in a flash partition where it can be read back at some
>  	  later point.
>  
> +config MTD_PSTORE
> +	tristate "Log panic/oops to an MTD buffer base on pstore"

                                                  based

> +	depends on PSTORE_BLKOOPS
> +	help
> +	  This enables panic and oops messages to be logged to a circular
> +	  buffer in a flash partition where it can be read back as files after
> +	  mounting pstore filesystem.
> +
> +	  If unsure, say N.
> +
>  config MTD_SWAP
>  	tristate "Swap on MTD device support"
>  	depends on MTD && SWAP
> diff --git a/drivers/mtd/Makefile b/drivers/mtd/Makefile
> index 56cc60ccc477..593d0593a038 100644
> --- a/drivers/mtd/Makefile
> +++ b/drivers/mtd/Makefile
> @@ -20,6 +20,7 @@ obj-$(CONFIG_RFD_FTL)		+= rfd_ftl.o
>  obj-$(CONFIG_SSFDC)		+= ssfdc.o
>  obj-$(CONFIG_SM_FTL)		+= sm_ftl.o
>  obj-$(CONFIG_MTD_OOPS)		+= mtdoops.o
> +obj-$(CONFIG_MTD_PSTORE)	+= mtdpstore.o
>  obj-$(CONFIG_MTD_SWAP)		+= mtdswap.o
>  
>  nftl-objs		:= nftlcore.o nftlmount.o
> diff --git a/drivers/mtd/mtdpstore.c b/drivers/mtd/mtdpstore.c
> new file mode 100644
> index 000000000000..ab4acd3a9011
> --- /dev/null
> +++ b/drivers/mtd/mtdpstore.c
> @@ -0,0 +1,530 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * MTD Oops/Panic loger for pstore/blk
> + *
> + * Copyright (C) 2019 WeiXiong Liao <liaoweixiong@gallwinnertech.com>
> + *
> + * 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.

The license text is not needed since you added SPDX tag.

> + *
> + */
> +#define pr_fmt(fmt) "mtdoops-pstore: " fmt
> +
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/blkoops.h>
> +#include <linux/mtd/mtd.h>
> +#include <linux/bitops.h>
> +
> +/* Maximum MTD partition size */
> +#define MTDPSTORE_MAX_MTD_SIZE (8 * 1024 * 1024)

                                  SZ_8M

> +
> +static struct mtdpstore_context {
> +	int index;
> +	struct blkoops_info bo_info;
> +	struct blkoops_device bo_dev;
> +	struct mtd_info *mtd;
> +	unsigned long *rmmap;		/* removed bit map */
> +	unsigned long *usedmap;		/* used bit map */
> +	/*
> +	 * used for panic write
> +	 * As there are no block_isbad for panic case, we should keep this
> +	 * status before panic to ensure panic_write not failed.
> +	 */
> +	unsigned long *badmap;		/* bad block bit map */
> +} oops_cxt;
> +
> +static int mtdpstore_block_isbad(struct mtdpstore_context *cxt, loff_t off)
> +{
> +	int ret;
> +	struct mtd_info *mtd = cxt->mtd;
> +	u64 blknum = div_u64(off, mtd->erasesize);
> +
> +	if (test_bit(blknum, cxt->badmap))
> +		return true;
> +	ret = mtd_block_isbad(mtd, off);
> +	if (ret < 0) {
> +		pr_err("mtd_block_isbad failed, aborting\n");
> +		return ret;
> +	} else if (ret > 0) {
> +		set_bit(blknum, cxt->badmap);
> +		return true;
> +	}
> +	return false;
> +}
> +
> +static inline int mtdpstore_panic_block_isbad(struct mtdpstore_context *cxt,
> +		loff_t off)
> +{
> +	struct mtd_info *mtd = cxt->mtd;
> +	u64 blknum = div_u64(off, mtd->erasesize);
> +
> +	return test_bit(blknum, cxt->badmap);
> +}
> +
> +static inline void mtdpstore_mark_used(struct mtdpstore_context *cxt,
> +		loff_t off)
> +{
> +	u64 zonenum = div_u64(off, cxt->bo_info.dmesg_size);
> +
> +	pr_debug("mark zone %llu used\n", zonenum);
> +	set_bit(zonenum, cxt->usedmap);
> +}
> +
> +static inline void mtdpstore_mark_unused(struct mtdpstore_context *cxt,
> +		loff_t off)
> +{
> +	u64 zonenum = div_u64(off, cxt->bo_info.dmesg_size);
> +
> +	pr_debug("mark zone %llu unused\n", zonenum);
> +	clear_bit(zonenum, cxt->usedmap);
> +}
> +
> +static inline void mtdpstore_block_mark_unused(struct mtdpstore_context *cxt,
> +		loff_t off)
> +{
> +	u64 zonenum = div_u64(off, cxt->bo_info.dmesg_size);
> +	u32 zonecnt = cxt->mtd->erasesize / cxt->bo_info.dmesg_size;
> +
> +	while (zonecnt > 0) {
> +		pr_debug("mark zone %llu unused\n", zonenum);
> +		clear_bit(zonenum, cxt->usedmap);
> +		zonenum++;
> +		zonecnt--;
> +	}
> +}
> +
> +static inline int mtdpstore_is_used(struct mtdpstore_context *cxt, loff_t off)
> +{
> +	u64 zonenum = div_u64(off, cxt->bo_info.dmesg_size);
> +	u64 blknum = div_u64(off, cxt->mtd->erasesize);
> +
> +	if (test_bit(blknum, cxt->badmap))
> +		return true;
> +	return test_bit(zonenum, cxt->usedmap);
> +}
> +
> +static int mtdpstore_block_is_used(struct mtdpstore_context *cxt,
> +		loff_t off)
> +{
> +	u64 zonenum = div_u64(off, cxt->bo_info.dmesg_size);
> +	u32 zonecnt = cxt->mtd->erasesize / cxt->bo_info.dmesg_size;
> +
> +	while (zonecnt > 0) {
> +		if (test_bit(zonenum, cxt->usedmap))
> +			return true;
> +		zonenum++;
> +		zonecnt--;
> +	}
> +	return false;
> +}
> +
> +static int mtdpstore_is_empty(struct mtdpstore_context *cxt, char *buf,
> +		size_t size)
> +{
> +	struct mtd_info *mtd = cxt->mtd;
> +	size_t sz;
> +	int i;
> +
> +	sz = min_t(uint32_t, size, mtd->writesize / 4);
> +	for (i = 0; i < sz; i++) {
> +		if (buf[i] != (char)0xFF)
> +			return false;
> +	}
> +	return true;
> +}
> +
> +static void mtdpstore_mark_removed(struct mtdpstore_context *cxt, loff_t off)
> +{
> +	u64 zonenum = div_u64(off, cxt->bo_info.dmesg_size);
> +
> +	pr_debug("mark zone %llu removed\n", zonenum);
> +	set_bit(zonenum, cxt->rmmap);
> +}
> +
> +static void mtdpstore_block_clear_removed(struct mtdpstore_context *cxt,
> +		loff_t off)
> +{
> +	u64 zonenum = div_u64(off, cxt->bo_info.dmesg_size);
> +	u32 zonecnt = cxt->mtd->erasesize / cxt->bo_info.dmesg_size;
> +
> +	while (zonecnt > 0) {
> +		clear_bit(zonenum, cxt->rmmap);
> +		zonenum++;
> +		zonecnt--;
> +	}
> +}
> +
> +static int mtdpstore_block_is_removed(struct mtdpstore_context *cxt,
> +		loff_t off)
> +{
> +	u64 zonenum = div_u64(off, cxt->bo_info.dmesg_size);
> +	u32 zonecnt = cxt->mtd->erasesize / cxt->bo_info.dmesg_size;
> +
> +	while (zonecnt > 0) {
> +		if (test_bit(zonenum, cxt->rmmap))
> +			return true;
> +		zonenum++;
> +		zonecnt--;
> +	}
> +	return false;
> +}
> +
> +static int mtdpstore_erase_do(struct mtdpstore_context *cxt, loff_t off)
> +{
> +	struct erase_info erase;
> +	int ret;
> +
> +	pr_debug("try to erase off 0x%llx\n", off);
> +	erase.len = cxt->mtd->erasesize;
> +	erase.addr = off;
> +	ret = mtd_erase(cxt->mtd, &erase);
> +	if (!ret)
> +		mtdpstore_block_clear_removed(cxt, off);
> +	else
> +		pr_err("erase of region [0x%llx, 0x%llx] on \"%s\" failed\n",
> +		       (unsigned long long)erase.addr,
> +		       (unsigned long long)erase.len, cxt->bo_info.device);
> +	return ret;
> +}
> +
> +/*
> + * called while removing file
> + *
> + * Avoiding over erasing, do erase only when all zones are removed or unused.
> + * Ensure to remove when unregister by reading, erasing and wrtiing back.
> + */
> +static ssize_t mtdpstore_erase(size_t size, loff_t off)
> +{
> +	struct mtdpstore_context *cxt = &oops_cxt;
> +
> +	if (mtdpstore_block_isbad(cxt, off))
> +		return -EIO;
> +
> +	mtdpstore_mark_unused(cxt, off);
> +
> +	if (likely(mtdpstore_block_is_used(cxt, off))) {
> +		mtdpstore_mark_removed(cxt, off);
> +		return 0;
> +	}
> +
> +	/* all zones are unused, erase it */
> +	off = ALIGN_DOWN(off, cxt->mtd->erasesize);
> +	return mtdpstore_erase_do(cxt, off);
> +}
> +
> +/*
> + * What is securety for mtdpstore?

              security

> + * As there is no erase for panic case, we should ensure at least one zone
> + * is writable. Otherwise, panic write will be failed.

                                          will fail.

> + * If zone is used, write operation will return -ENEXT, which means that
> + * pstore/blk will try one by one until get a empty zone. So, it's no need

                                           it gets an empty zone. So it
                                           is not needed to ...
    
> + * to ensure next zone is empty, but at least one.

               the

> + */
> +static int mtdpstore_security(struct mtdpstore_context *cxt, loff_t off)
> +{
> +	int ret = 0, i;
> +	u32 zonenum = (u32)div_u64(off, cxt->bo_info.dmesg_size);
> +	u32 zonecnt = (u32)div_u64(cxt->mtd->size, cxt->bo_info.dmesg_size);
> +	u32 blkcnt = (u32)div_u64(cxt->mtd->size, cxt->mtd->erasesize);
> +	u32 erasesize = cxt->mtd->erasesize;
> +
> +	for (i = 0; i < zonecnt; i++) {
> +		u32 num = (zonenum + i) % zonecnt;
> +
> +		/* found empty zone */
> +		if (!test_bit(num, cxt->usedmap))
> +			return 0;
> +	}
> +
> +	/* If there is no any empty zone, we have no way but to do erase */
> +	off = ALIGN_DOWN(off, erasesize);
> +	while (blkcnt--) {
> +		div64_u64_rem(off + erasesize, cxt->mtd->size, (u64 *)&off);
> +
> +		if (mtdpstore_block_isbad(cxt, off))
> +			continue;
> +
> +		ret = mtdpstore_erase_do(cxt, off);
> +		if (!ret) {
> +			mtdpstore_block_mark_unused(cxt, off);
> +			break;
> +		}
> +	}
> +
> +	if (ret)
> +		pr_err("all blocks bad!\n");
> +	pr_debug("end security\n");
> +	return ret;
> +}
> +
> +static ssize_t mtdpstore_write(const char *buf, size_t size, loff_t off)
> +{
> +	struct mtdpstore_context *cxt = &oops_cxt;
> +	size_t retlen;
> +	int ret;
> +
> +	if (mtdpstore_block_isbad(cxt, off))
> +		return -ENEXT;
> +
> +	/* zone is used, please try next one */
> +	if (mtdpstore_is_used(cxt, off))
> +		return -ENEXT;
> +
> +	pr_debug("try to write off 0x%llx size %zu\n", off, size);
> +	ret = mtd_write(cxt->mtd, off, size, &retlen, (u_char *)buf);
> +	if (ret < 0 || retlen != size) {
> +		pr_err("write failure at %lld (%zu of %zu written), err %d\n",
> +				off, retlen, size, ret);
> +		return -EIO;
> +	}
> +	mtdpstore_mark_used(cxt, off);
> +
> +	mtdpstore_security(cxt, off);
> +	return retlen;
> +}
> +
> +/*
> + * All zones will be read as pstore/blk will read zone one by one when do
> + * recover.
> + */
> +static ssize_t mtdpstore_read(char *buf, size_t size, loff_t off)
> +{
> +	struct mtdpstore_context *cxt = &oops_cxt;
> +	size_t retlen;
> +	int ret;
> +
> +	if (mtdpstore_block_isbad(cxt, off))
> +		return -ENEXT;
> +
> +	pr_debug("try to read off 0x%llx size %zu\n", off, size);
> +	ret = mtd_read(cxt->mtd, off, size, &retlen, (u_char *)buf);
> +	if ((ret < 0 && !mtd_is_bitflip(ret)) || size != retlen)  {

IIRC size != retlen does not mean it failed, but that you should
continue reading after retlen bytes, no?

Also, mtd_is_bitflip() does not mean that you are reading a false
buffer, but that the data has been corrected as it contained bitflips.
mtd_is_eccerr() however, would be meaningful.

> +		pr_err("read failure at %lld (%zu of %zu read), err %d\n",
> +				off, retlen, size, ret);
> +		return -EIO;
> +	}
> +
> +	if (mtdpstore_is_empty(cxt, buf, size))
> +		mtdpstore_mark_unused(cxt, off);
> +	else
> +		mtdpstore_mark_used(cxt, off);
> +
> +	mtdpstore_security(cxt, off);
> +	return retlen;
> +}
> +
> +static ssize_t mtdpstore_panic_write(const char *buf, size_t size, loff_t off)
> +{
> +	struct mtdpstore_context *cxt = &oops_cxt;
> +	size_t retlen;
> +	int ret;
> +
> +	if (mtdpstore_panic_block_isbad(cxt, off))
> +		return -ENEXT;
> +
> +	/* zone is used, please try next one */
> +	if (mtdpstore_is_used(cxt, off))
> +		return -ENEXT;
> +
> +	ret = mtd_panic_write(cxt->mtd, off, size, &retlen, (u_char *)buf);
> +	if (ret < 0 || size != retlen) {
> +		pr_err("panic write failure at %lld (%zu of %zu read), err %d\n",
> +				off, retlen, size, ret);
> +		return -EIO;
> +	}
> +	mtdpstore_mark_used(cxt, off);
> +
> +	return retlen;
> +}
> +
> +static void mtdpstore_notify_add(struct mtd_info *mtd)
> +{
> +	int ret;
> +	struct mtdpstore_context *cxt = &oops_cxt;
> +	struct blkoops_info *info = &cxt->bo_info;
> +	unsigned long longcnt;
> +
> +	if (!strcmp(mtd->name, info->device))
> +		cxt->index = mtd->index;
> +
> +	if (mtd->index != cxt->index || cxt->index < 0)
> +		return;
> +
> +	pr_debug("found matching MTD device %s\n", mtd->name);
> +
> +	if (mtd->size < info->dmesg_size * 2) {
> +		pr_err("MTD partition %d not big enough\n", mtd->index);
> +		return;
> +	}
> +	if (mtd->erasesize < info->dmesg_size) {
> +		pr_err("eraseblock size of MTD partition %d too small\n",
> +				mtd->index);

What is the usual size of dmesg? Could this check be too limiting?

> +		return;
> +	}
> +	if (unlikely(info->dmesg_size % mtd->writesize)) {
> +		pr_err("record size %lu KB must align to write size %d KB\n",
> +				info->dmesg_size / 1024,
> +				mtd->writesize / 1024);

This condition is weird, why would you check this?

> +		return;
> +	}
> +	if (unlikely(mtd->size > MTDPSTORE_MAX_MTD_SIZE)) {
> +		pr_err("mtd%d is too large (limit is %d MiB)\n",
> +				mtd->index,
> +				MTDPSTORE_MAX_MTD_SIZE / 1024 / 1024);

Same question? I could understand that it is easier to manage blocks
knowing their maximum number though.

> +		return;
> +	}
> +
> +	longcnt = BITS_TO_LONGS(div_u64(mtd->size, info->dmesg_size));
> +	cxt->rmmap = kcalloc(longcnt, sizeof(long), GFP_KERNEL);
> +	cxt->usedmap = kcalloc(longcnt, sizeof(long), GFP_KERNEL);
> +
> +	longcnt = BITS_TO_LONGS(div_u64(mtd->size, mtd->erasesize));
> +	cxt->badmap = kcalloc(longcnt, sizeof(long), GFP_KERNEL);
> +
> +	cxt->bo_dev.total_size = mtd->size;
> +	/* just support dmesg right now */
> +	cxt->bo_dev.flags = BLKOOPS_DEV_SUPPORT_DMESG;
> +	cxt->bo_dev.read = mtdpstore_read;
> +	cxt->bo_dev.write = mtdpstore_write;
> +	cxt->bo_dev.erase = mtdpstore_erase;
> +	cxt->bo_dev.panic_write = mtdpstore_panic_write;
> +
> +	ret = blkoops_register_device(&cxt->bo_dev);
> +	if (ret) {
> +		pr_err("mtd%d register to blkoops failed\n", mtd->index);
> +		return;
> +	}
> +	cxt->mtd = mtd;
> +	pr_info("Attached to MTD device %d\n", mtd->index);
> +}
> +
> +static int mtdpstore_flush_removed_do(struct mtdpstore_context *cxt,
> +		loff_t off, size_t size)
> +{
> +	struct mtd_info *mtd = cxt->mtd;
> +	u_char *buf;
> +	int ret;
> +	size_t retlen;
> +	struct erase_info erase;
> +
> +	buf = kmalloc(mtd->erasesize, GFP_KERNEL);
> +	if (!buf)
> +		return -ENOMEM;
> +
> +	/* 1st. read to cache */
> +	ret = mtd_read(mtd, off, mtd->erasesize, &retlen, buf);
> +	if (ret || retlen != mtd->erasesize)
> +		goto free;
> +
> +	/* 2nd. erase block */
> +	erase.len = mtd->erasesize;
> +	erase.addr = off;
> +	ret = mtd_erase(mtd, &erase);
> +	if (ret)
> +		goto free;
> +
> +	/* 3rd. write back */
> +	while (size) {
> +		unsigned int zonesize = cxt->bo_info.dmesg_size;
> +
> +		/* remove must clear used bit */
> +		if (mtdpstore_is_used(cxt, off))
> +			mtd_write(mtd, off, zonesize, &retlen, buf);

Besides the fact that should definitely check the write return code, I
don't understand what you do in this function. What does
flush_removed_do mean?

> +
> +		off += zonesize;
> +		size -= min_t(unsigned int, zonesize, size);
> +	}
> +
> +free:
> +	kfree(buf);
> +	return ret;
> +}
> +
> +static int mtdpstore_flush_removed(struct mtdpstore_context *cxt)
> +{
> +	struct mtd_info *mtd = cxt->mtd;
> +	int ret;
> +	loff_t off;
> +	u32 blkcnt = (u32)div_u64(mtd->size, mtd->erasesize);
> +
> +	for (off = 0; blkcnt > 0; blkcnt--, off += mtd->erasesize) {
> +		ret = mtdpstore_block_is_removed(cxt, off);
> +		if (!ret) {
> +			off += mtd->erasesize;
> +			continue;
> +		}
> +
> +		ret = mtdpstore_flush_removed_do(cxt, off, mtd->erasesize);
> +		if (ret)
> +			return ret;
> +	}
> +	return 0;
> +}
> +
> +static void mtdpstore_notify_remove(struct mtd_info *mtd)
> +{
> +	struct mtdpstore_context *cxt = &oops_cxt;
> +
> +	if (mtd->index != cxt->index || cxt->index < 0)
> +		return;
> +
> +	mtdpstore_flush_removed(cxt);
> +
> +	blkoops_unregister_device(&cxt->bo_dev);
> +	kfree(cxt->badmap);
> +	kfree(cxt->usedmap);
> +	kfree(cxt->rmmap);
> +	cxt->mtd = NULL;
> +	cxt->index = -1;
> +}
> +
> +static struct mtd_notifier mtdpstore_notifier = {
> +	.add	= mtdpstore_notify_add,
> +	.remove	= mtdpstore_notify_remove,
> +};
> +
> +static int __init mtdpstore_init(void)
> +{
> +	int ret;
> +	struct mtdpstore_context *cxt = &oops_cxt;
> +	struct blkoops_info *info = &cxt->bo_info;
> +
> +	ret = blkoops_info(info);
> +	if (unlikely(ret))
> +		return ret;
> +
> +	if (strlen(info->device) == 0) {
> +		pr_err("mtd device must be supplied\n");
> +		return -EINVAL;
> +	}
> +	if (!info->dmesg_size) {
> +		pr_err("no recorder enabled\n");
> +		return -EINVAL;
> +	}
> +
> +	/* Setup the MTD device to use */
> +	ret = kstrtoint((char *)info->device, 0, &cxt->index);
> +	if (ret)
> +		cxt->index = -1;
> +
> +	register_mtd_user(&mtdpstore_notifier);
> +	return 0;
> +}
> +module_init(mtdpstore_init);
> +
> +static void __exit mtdpstore_exit(void)
> +{
> +	unregister_mtd_user(&mtdpstore_notifier);
> +}
> +module_exit(mtdpstore_exit);
> +
> +MODULE_LICENSE("GPL");
> +MODULE_AUTHOR("WeiXiong Liao <liaoweixiong@allwinnertech.com>");
> +MODULE_DESCRIPTION("MTD Oops/Panic console logger/driver");




Thanks,
Miquèl