Re: [EXT] Re: [PATCH v5 1/2] mmc: Support kmsg dumper based on pstore/blk

[Ulf Hansson <ulf.hansson@linaro.org>]

On Mon, 7 Jun 2021 at 14:37, Bhaskara Budiredla <bbudiredla@marvell.com> wrote:
>
> [...]
> >What patches are you referring to?
>
> I was referring to this patch.
> http://git.infradead.org/users/hch/misc.git/shortlog/refs/heads/pstore

Alright. I didn't know about these, thanks for the pointer. Looks like
a big step in the right direction.

I guess Christoph simply has been busy with other things. Perhaps you
should ask if you can help and pick up from where he left the series?

Kind regards
Uffe

>
> Thanks,
> Bhaskara
>
> >-----Original Message-----
> >From: Ulf Hansson <ulf.hansson@linaro.org>
> >Sent: Monday, June 7, 2021 4:47 PM
> >To: Bhaskara Budiredla <bbudiredla@marvell.com>
> >Cc: Kees Cook <keescook@chromium.org>; Colin Cross
> ><ccross@android.com>; Tony Luck <tony.luck@intel.com>; Sunil Kovvuri
> >Goutham <sgoutham@marvell.com>; linux-mmc@vger.kernel.org; Linux
> >Kernel Mailing List <linux-kernel@vger.kernel.org>; linux-block <linux-
> >block@vger.kernel.org>; Jens Axboe <axboe@kernel.dk>; Christoph Hellwig
> ><hch@lst.de>
> >Subject: Re: [EXT] Re: [PATCH v5 1/2] mmc: Support kmsg dumper based on
> >pstore/blk
> >
> >On Sat, 5 Jun 2021 at 12:31, Bhaskara Budiredla <bbudiredla@marvell.com>
> >wrote:
> >>
> >> Hi Uffe,
> >>
> >> With due respect to pstore/blk subsystem changes we have been waiting
> >since long time to see Christoph patches taken.
> >
> >What patches are you referring to?
> >
> >> But unfortunately it is still finding at that same stage only. Can you
> >> please take up my patch in the current form (which is based on current
> >> pstore/blk framework) instead of waiting indefinitely. If pstore/blk comes up
> >with the changes that has been discussed by you previously, I will further
> >submit the corresponding changes for eMMC devices.
> >
> >No, I am sorry, but that's not the way it works.
> >
> >If you really want to move things forward, I would suggest that you try to
> >implement something along the lines of what I have suggested.
> >Another option is to post an RFD/RFC so as solution can be discussed with the
> >relevant people.
> >
> >Kind regards
> >Uffe
> >
> >>
> >> Thanks,
> >> Bhaskara
> >>
> >> >-----Original Message-----
> >> >From: Ulf Hansson <ulf.hansson@linaro.org>
> >> >Sent: Wednesday, January 20, 2021 8:36 PM
> >> >To: Bhaskara Budiredla <bbudiredla@marvell.com>; Kees Cook
> >> ><keescook@chromium.org>
> >> >Cc: Colin Cross <ccross@android.com>; Tony Luck
> >> ><tony.luck@intel.com>; Sunil Kovvuri Goutham <sgoutham@marvell.com>;
> >> >linux- mmc@vger.kernel.org; Linux Kernel Mailing List <linux-
> >> >kernel@vger.kernel.org>; linux-block <linux-block@vger.kernel.org>;
> >> >Jens Axboe <axboe@kernel.dk>; Christoph Hellwig <hch@lst.de>
> >> >Subject: [EXT] Re: [PATCH v5 1/2] mmc: Support kmsg dumper based on
> >> >pstore/blk
> >> >
> >> >External Email
> >> >
> >> >---------------------------------------------------------------------
> >> >-
> >> >+ linux-block, Jens, Christoph
> >> >
> >> >On Wed, 20 Jan 2021 at 13:11, Bhaskara Budiredla
> >> ><bbudiredla@marvell.com> wrote:
> >> >>
> >> >> This patch introduces to mmcpstore. The functioning of mmcpstore is
> >> >> similar to mtdpstore. mmcpstore works on FTL based flash devices
> >> >> whereas mtdpstore works on raw flash devices. When the system
> >> >> crashes, mmcpstore stores the kmsg panic and oops logs to a user
> >> >> specified MMC device.
> >> >>
> >> >> It collects the details about the host MMC device through
> >> >> pstore/blk "blkdev" parameter. The user can specify the MMC device
> >> >> in many ways by checking in Documentation/admin-guide/pstore-blk.rst.
> >> >>
> >> >> The individual mmc host drivers have to define suitable polling and
> >> >> cleanup subroutines to write kmsg panic/oops logs through mmcpstore.
> >> >> These new host operations are needed as pstore panic write runs
> >> >> with interrupts disabled.
> >> >
> >> >Okay, let me again try to clarify on how I see this to move this forward.
> >> >
> >> >1)
> >> >In my opinion, pstore shouldn't be using callbacks for *regular* I/O
> >> >read/writes. It's upside-down of how the storage stack is designed to work.
> >> >
> >> >Instead, pstore should be implemented as a regular filesystem, that
> >> >can be mounted on top of a regular block device partition. In this
> >> >way, the lower layer block device drivers (as mmc), don't need
> >> >special support for pstore, the regular I/O block read/write path will just
> >work as is.
> >> >
> >> >2)
> >> >When it comes to supporting *panic* writes for pstore, things become
> >> >a bit more complicated. For sure some adaptations are needed in each
> >> >block device driver to support this.
> >> >
> >> >However, the current method means relying on the lower level block
> >> >device driver to figure out the pstore partition. Based on that, it
> >> >should then register itself for pstore support and hook up callbacks
> >> >for the corresponding block device driver instance, at least that is
> >> >what it looks like to me. Again, I think this is upside-down from the
> >> >storage stack perspective. The partition to use for pstore, should be based
> >upon its file system mount point.
> >> >
> >> >Furthermore, I think the responsibility for lower layer block device
> >> >drivers should instead be to just "register/announce" themselves as
> >> >capable of supporting "panic writes", if they can. Exactly how to
> >> >best do this, probably needs to be discussed further with the block
> >> >device people, I think. I have looped in Jens and Christoph, perhaps they
> >can share their opinion in this.
> >> >
> >> >That said, it looks to me that pstore needs more work before it's
> >> >ready to be adopted for generic support in block device drivers.
> >> >
> >> >Kind regards
> >> >Uffe
> >> >
> >> >>
> >> >> Signed-off-by: Bhaskara Budiredla <bbudiredla@marvell.com>
> >> >> ---
> >> >>  drivers/mmc/core/Kconfig     |  14 ++-
> >> >>  drivers/mmc/core/Makefile    |   1 +
> >> >>  drivers/mmc/core/block.c     |  19 +++
> >> >>  drivers/mmc/core/block.h     |   9 ++
> >> >>  drivers/mmc/core/core.c      |  44 +++++++
> >> >>  drivers/mmc/core/mmcpstore.c | 227
> >> >+++++++++++++++++++++++++++++++++++
> >> >>  include/linux/mmc/core.h     |   5 +
> >> >>  include/linux/mmc/host.h     |  12 ++
> >> >>  8 files changed, 330 insertions(+), 1 deletion(-)  create mode
> >> >> 100644 drivers/mmc/core/mmcpstore.c
> >> >>
> >> >> diff --git a/drivers/mmc/core/Kconfig b/drivers/mmc/core/Kconfig
> >> >> index
> >> >> c12fe13e4b14..4c651da4f2d2 100644
> >> >> --- a/drivers/mmc/core/Kconfig
> >> >> +++ b/drivers/mmc/core/Kconfig
> >> >> @@ -34,9 +34,22 @@ config PWRSEQ_SIMPLE
> >> >>           This driver can also be built as a module. If so, the module
> >> >>           will be called pwrseq_simple.
> >> >>
> >> >> +config MMC_PSTORE_BACKEND
> >> >> +       bool "Log panic/oops to a MMC buffer"
> >> >> +       depends on MMC_BLOCK
> >> >> +       help
> >> >> +         This option will let you create platform backend to store kmsg
> >> >> +         crash dumps to a user specified MMC device. This is primarily
> >> >> +         based on pstore/blk.
> >> >> +
> >> >> +config MMC_PSTORE
> >> >> +       tristate
> >> >> +       select PSTORE_BLK
> >> >> +
> >> >>  config MMC_BLOCK
> >> >>         tristate "MMC block device driver"
> >> >>         depends on BLOCK
> >> >> +       select MMC_PSTORE if MMC_PSTORE_BACKEND=y
> >> >>         default y
> >> >>         help
> >> >>           Say Y here to enable the MMC block device driver support.
> >> >> @@ -80,4 +93,3 @@ config MMC_TEST
> >> >>
> >> >>           This driver is only of interest to those developing or
> >> >>           testing a host driver. Most people should say N here.
> >> >> -
> >> >> diff --git a/drivers/mmc/core/Makefile b/drivers/mmc/core/Makefile
> >> >> index 95ffe008ebdf..7cb9a3af4827 100644
> >> >> --- a/drivers/mmc/core/Makefile
> >> >> +++ b/drivers/mmc/core/Makefile
> >> >> @@ -16,5 +16,6 @@ obj-$(CONFIG_PWRSEQ_EMMC)     +=
> >pwrseq_emmc.o
> >> >>  mmc_core-$(CONFIG_DEBUG_FS)    += debugfs.o
> >> >>  obj-$(CONFIG_MMC_BLOCK)                += mmc_block.o
> >> >>  mmc_block-objs                 := block.o queue.o
> >> >> +mmc_block-$(CONFIG_MMC_PSTORE) += mmcpstore.o
> >> >>  obj-$(CONFIG_MMC_TEST)         += mmc_test.o
> >> >>  obj-$(CONFIG_SDIO_UART)                += sdio_uart.o
> >> >> diff --git a/drivers/mmc/core/block.c b/drivers/mmc/core/block.c
> >> >> index
> >> >> 42e27a298218..6592722cd7b2 100644
> >> >> --- a/drivers/mmc/core/block.c
> >> >> +++ b/drivers/mmc/core/block.c
> >> >> @@ -2870,6 +2870,21 @@ static void mmc_blk_remove_debugfs(struct
> >> >> mmc_card *card,
> >> >>
> >> >>  #endif /* CONFIG_DEBUG_FS */
> >> >>
> >> >> +#if IS_ENABLED(CONFIG_MMC_PSTORE)
> >> >> +sector_t mmc_blk_get_part(struct mmc_card *card, int part_num,
> >> >> +sector_t *size) {
> >> >> +       struct mmc_blk_data *md = dev_get_drvdata(&card->dev);
> >> >> +       struct gendisk *disk = md->disk;
> >> >> +       struct disk_part_tbl *part_tbl = disk->part_tbl;
> >> >> +
> >> >> +       if (part_num < 0 || part_num >= part_tbl->len)
> >> >> +               return 0;
> >> >> +
> >> >> +       *size = part_tbl->part[part_num]->nr_sects << SECTOR_SHIFT;
> >> >> +       return part_tbl->part[part_num]->start_sect;
> >> >> +}
> >> >> +#endif
> >> >> +
> >> >>  static int mmc_blk_probe(struct mmc_card *card)  {
> >> >>         struct mmc_blk_data *md, *part_md; @@ -2913,6 +2928,9 @@
> >> >> static int mmc_blk_probe(struct mmc_card *card)
> >> >>                         goto out;
> >> >>         }
> >> >>
> >> >> +       if (mmc_card_mmc(card) || mmc_card_sd(card))
> >> >> +               mmcpstore_card_set(card, md->disk->disk_name);
> >> >> +
> >> >>         /* Add two debugfs entries */
> >> >>         mmc_blk_add_debugfs(card, md);
> >> >>
> >> >> @@ -3060,6 +3078,7 @@ static void __exit mmc_blk_exit(void)
> >> >>         unregister_blkdev(MMC_BLOCK_MAJOR, "mmc");
> >> >>         unregister_chrdev_region(mmc_rpmb_devt, MAX_DEVICES);
> >> >>         bus_unregister(&mmc_rpmb_bus_type);
> >> >> +       unregister_mmcpstore();
> >> >>  }
> >> >>
> >> >>  module_init(mmc_blk_init);
> >> >> diff --git a/drivers/mmc/core/block.h b/drivers/mmc/core/block.h
> >> >> index
> >> >> 31153f656f41..2a4ee5568194 100644
> >> >> --- a/drivers/mmc/core/block.h
> >> >> +++ b/drivers/mmc/core/block.h
> >> >> @@ -16,5 +16,14 @@ void mmc_blk_mq_recovery(struct mmc_queue
> >> >*mq);
> >> >> struct work_struct;
> >> >>
> >> >>  void mmc_blk_mq_complete_work(struct work_struct *work);
> >> >> +#if IS_ENABLED(CONFIG_MMC_PSTORE)
> >> >> +sector_t mmc_blk_get_part(struct mmc_card *card, int part_num,
> >> >> +sector_t *size); void mmcpstore_card_set(struct mmc_card *card,
> >> >> +const char *disk_name); void unregister_mmcpstore(void); #else
> >> >> +static inline void mmcpstore_card_set(struct mmc_card *card,
> >> >> +                                       const char *disk_name) {}
> >> >> +static inline void unregister_mmcpstore(void) {} #endif
> >> >>
> >> >>  #endif
> >> >> diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
> >> >> index 19f1ee57fb34..7ad7ff1cab8c 100644
> >> >> --- a/drivers/mmc/core/core.c
> >> >> +++ b/drivers/mmc/core/core.c
> >> >> @@ -569,6 +569,30 @@ int mmc_cqe_recovery(struct mmc_host *host)
> >}
> >> >> EXPORT_SYMBOL(mmc_cqe_recovery);
> >> >>
> >> >> +#if IS_ENABLED(CONFIG_MMC_PSTORE)
> >> >> +/**
> >> >> + *     mmc_wait_for_pstore_req - initiate a blocking mmc request
> >> >> + *     @host: MMC host to start command
> >> >> + *     @mrq: MMC request to start
> >> >> + *
> >> >> + *     Start a blocking MMC request for a host and wait for the request
> >> >> + *     to complete that is based on polling and timeout.
> >> >> + */
> >> >> +void mmc_wait_for_pstore_req(struct mmc_host *host, struct
> >> >> +mmc_request *mrq) {
> >> >> +       unsigned int timeout;
> >> >> +
> >> >> +       host->ops->req_cleanup_pending(host);
> >> >> +       mmc_start_request(host, mrq);
> >> >> +
> >> >> +       if (mrq->data) {
> >> >> +               timeout = mrq->data->timeout_ns / NSEC_PER_MSEC;
> >> >> +               host->ops->req_completion_poll(host, timeout);
> >> >> +       }
> >> >> +}
> >> >> +EXPORT_SYMBOL(mmc_wait_for_pstore_req);
> >> >> +#endif
> >> >> +
> >> >>  /**
> >> >>   *     mmc_is_req_done - Determine if a 'cap_cmd_during_tfr' request is
> >> >done
> >> >>   *     @host: MMC host
> >> >> @@ -817,6 +841,26 @@ int __mmc_claim_host(struct mmc_host *host,
> >> >> struct mmc_ctx *ctx,  }  EXPORT_SYMBOL(__mmc_claim_host);
> >> >>
> >> >> +#if IS_ENABLED(CONFIG_MMC_PSTORE)
> >> >> +/**
> >> >> + *     mmc_claim_host_async - claim host in atomic context
> >> >> + *     @host: mmc host to claim
> >> >> + *
> >> >> + *     This routine may be called in panic/oops scenarios.
> >> >> + *     Return zero with host claim success, else busy status.
> >> >> + */
> >> >> +int mmc_claim_host_async(struct mmc_host *host) {
> >> >> +       if (!host->claimed && pm_runtime_active(mmc_dev(host))) {
> >> >> +               host->claimed = 1;
> >> >> +               return 0;
> >> >> +       }
> >> >> +
> >> >> +       return -EBUSY;
> >> >> +}
> >> >> +EXPORT_SYMBOL(mmc_claim_host_async);
> >> >> +#endif
> >> >> +
> >> >>  /**
> >> >>   *     mmc_release_host - release a host
> >> >>   *     @host: mmc host to release
> >> >> diff --git a/drivers/mmc/core/mmcpstore.c
> >> >> b/drivers/mmc/core/mmcpstore.c new file mode 100644 index
> >> >> 000000000000..f783ea215f18
> >> >> --- /dev/null
> >> >> +++ b/drivers/mmc/core/mmcpstore.c
> >> >> @@ -0,0 +1,227 @@
> >> >> +// SPDX-License-Identifier: GPL-2.0
> >> >> +/*
> >> >> + * MMC pstore support based on pstore/blk
> >> >> + *
> >> >> + * Copyright (c) 2020 Marvell.
> >> >> + * Author: Bhaskara Budiredla <bbudiredla@marvell.com>  */
> >> >> +
> >> >> +#define pr_fmt(fmt) "mmcpstore: " fmt
> >> >> +
> >> >> +#include <linux/kernel.h>
> >> >> +#include <linux/module.h>
> >> >> +#include <linux/pstore_blk.h>
> >> >> +#include <linux/blkdev.h>
> >> >> +#include <linux/mount.h>
> >> >> +#include <linux/slab.h>
> >> >> +#include <linux/mmc/mmc.h>
> >> >> +#include <linux/mmc/host.h>
> >> >> +#include <linux/mmc/card.h>
> >> >> +#include <linux/scatterlist.h>
> >> >> +#include "block.h"
> >> >> +#include "card.h"
> >> >> +#include "core.h"
> >> >> +
> >> >> +static struct mmcpstore_context {
> >> >> +       char dev_name[BDEVNAME_SIZE];
> >> >> +       int partno;
> >> >> +       sector_t start_sect;
> >> >> +       sector_t size;
> >> >> +       struct pstore_blk_config conf;
> >> >> +       struct pstore_blk_info info;
> >> >> +
> >> >> +       struct mmc_card *card;
> >> >> +       struct mmc_request *mrq;
> >> >> +} oops_cxt;
> >> >> +
> >> >> +static void mmc_prep_req(struct mmc_request *mrq,
> >> >> +               unsigned int sect_offset, unsigned int nsects,
> >> >> +               struct scatterlist *sg, u32 opcode, unsigned int
> >> >> +flags) {
> >> >> +       mrq->cmd->opcode = opcode;
> >> >> +       mrq->cmd->arg = sect_offset;
> >> >> +       mrq->cmd->flags = MMC_RSP_R1 | MMC_CMD_ADTC;
> >> >> +
> >> >> +       if (nsects == 1) {
> >> >> +               mrq->stop = NULL;
> >> >> +       } else {
> >> >> +               mrq->stop->opcode = MMC_STOP_TRANSMISSION;
> >> >> +               mrq->stop->arg = 0;
> >> >> +               mrq->stop->flags = MMC_RSP_R1B | MMC_CMD_AC;
> >> >> +       }
> >> >> +
> >> >> +       mrq->data->blksz = SECTOR_SIZE;
> >> >> +       mrq->data->blocks = nsects;
> >> >> +       mrq->data->flags = flags;
> >> >> +       mrq->data->sg = sg;
> >> >> +       mrq->data->sg_len = 1;
> >> >> +}
> >> >> +
> >> >> +static int mmcpstore_panic_write_req(const char *buf,
> >> >> +               unsigned int nsects, unsigned int sect_offset) {
> >> >> +       struct mmcpstore_context *cxt = &oops_cxt;
> >> >> +       struct mmc_request *mrq = cxt->mrq;
> >> >> +       struct mmc_card *card = cxt->card;
> >> >> +       struct mmc_host *host = card->host;
> >> >> +       struct scatterlist sg;
> >> >> +       u32 opcode;
> >> >> +       int ret;
> >> >> +
> >> >> +       opcode = (nsects > 1) ? MMC_WRITE_MULTIPLE_BLOCK :
> >> >MMC_WRITE_BLOCK;
> >> >> +       mmc_prep_req(mrq, sect_offset, nsects, &sg, opcode,
> >> >MMC_DATA_WRITE);
> >> >> +       sg_init_one(&sg, buf, (nsects << SECTOR_SHIFT));
> >> >> +       mmc_set_data_timeout(mrq->data, cxt->card);
> >> >> +
> >> >> +       ret = mmc_claim_host_async(host);
> >> >> +       if (ret)
> >> >> +               return ret;
> >> >> +
> >> >> +       mmc_wait_for_pstore_req(host, mrq);
> >> >> +       return 0;
> >> >> +}
> >> >> +
> >> >> +static int mmcpstore_panic_write(const char *buf, sector_t off,
> >> >> +sector_t sects) {
> >> >> +       struct mmcpstore_context *cxt = &oops_cxt;
> >> >> +       int ret;
> >> >> +
> >> >> +       ret = mmcpstore_panic_write_req(buf, sects, cxt->start_sect + off);
> >> >> +       if (ret)
> >> >> +               return ret;
> >> >> +
> >> >> +       return 0;
> >> >> +}
> >> >> +
> >> >> +static struct block_device *mmcpstore_open_backend(const char
> >> >> +*device) {
> >> >> +       struct block_device *bdev;
> >> >> +       dev_t devt;
> >> >> +
> >> >> +       bdev = blkdev_get_by_path(device, FMODE_READ, NULL);
> >> >> +       if (IS_ERR(bdev)) {
> >> >> +               devt = name_to_dev_t(device);
> >> >> +               if (devt == 0)
> >> >> +                       return ERR_PTR(-ENODEV);
> >> >> +
> >> >> +               bdev = blkdev_get_by_dev(devt, FMODE_READ, NULL);
> >> >> +               if (IS_ERR(bdev))
> >> >> +                       return bdev;
> >> >> +       }
> >> >> +
> >> >> +       return bdev;
> >> >> +}
> >> >> +
> >> >> +static void mmcpstore_close_backend(struct block_device *bdev) {
> >> >> +       if (!bdev)
> >> >> +               return;
> >> >> +       blkdev_put(bdev, FMODE_READ); }
> >> >> +
> >> >> +void mmcpstore_card_set(struct mmc_card *card, const char
> >> >> +*disk_name) {
> >> >> +       struct mmcpstore_context *cxt = &oops_cxt;
> >> >> +       struct pstore_blk_config *conf = &cxt->conf;
> >> >> +       struct pstore_blk_info *info = &cxt->info;
> >> >> +       struct block_device *bdev;
> >> >> +       struct mmc_command *stop;
> >> >> +       struct mmc_command *cmd;
> >> >> +       struct mmc_request *mrq;
> >> >> +       struct mmc_data *data;
> >> >> +       int ret;
> >> >> +
> >> >> +       ret = pstore_blk_get_config(conf);
> >> >> +       if (!conf->device[0]) {
> >> >> +               pr_debug("psblk backend is empty\n");
> >> >> +               return;
> >> >> +       }
> >> >> +
> >> >> +       /* Multiple backend devices not allowed */
> >> >> +       if (cxt->dev_name[0])
> >> >> +               return;
> >> >> +
> >> >> +       bdev =  mmcpstore_open_backend(conf->device);
> >> >> +       if (IS_ERR(bdev)) {
> >> >> +               pr_err("%s failed to open with %ld\n",
> >> >> +                               conf->device, PTR_ERR(bdev));
> >> >> +               return;
> >> >> +       }
> >> >> +
> >> >> +       bdevname(bdev, cxt->dev_name);
> >> >> +       cxt->partno = bdev->bd_part->partno;
> >> >> +       mmcpstore_close_backend(bdev);
> >> >> +
> >> >> +       if (strncmp(cxt->dev_name, disk_name, strlen(disk_name)))
> >> >> +               return;
> >> >> +
> >> >> +       cxt->start_sect = mmc_blk_get_part(card, cxt->partno, &cxt->size);
> >> >> +       if (!cxt->start_sect) {
> >> >> +               pr_err("Non-existent partition %d selected\n", cxt->partno);
> >> >> +               return;
> >> >> +       }
> >> >> +
> >> >> +       /* Check for host mmc panic write polling function definitions */
> >> >> +       if (!card->host->ops->req_cleanup_pending ||
> >> >> +                       !card->host->ops->req_completion_poll)
> >> >> +               return;
> >> >> +
> >> >> +       cxt->card = card;
> >> >> +
> >> >> +       mrq = kzalloc(sizeof(struct mmc_request), GFP_KERNEL);
> >> >> +       if (!mrq)
> >> >> +               goto out;
> >> >> +
> >> >> +       cmd = kzalloc(sizeof(struct mmc_command), GFP_KERNEL);
> >> >> +       if (!cmd)
> >> >> +               goto free_mrq;
> >> >> +
> >> >> +       stop = kzalloc(sizeof(struct mmc_command), GFP_KERNEL);
> >> >> +       if (!stop)
> >> >> +               goto free_cmd;
> >> >> +
> >> >> +       data = kzalloc(sizeof(struct mmc_data), GFP_KERNEL);
> >> >> +       if (!data)
> >> >> +               goto free_stop;
> >> >> +
> >> >> +       mrq->cmd = cmd;
> >> >> +       mrq->data = data;
> >> >> +       mrq->stop = stop;
> >> >> +       cxt->mrq = mrq;
> >> >> +
> >> >> +       info->major = MMC_BLOCK_MAJOR;
> >> >> +       info->flags = PSTORE_FLAGS_DMESG;
> >> >> +       info->panic_write = mmcpstore_panic_write;
> >> >> +       ret = register_pstore_blk(info);
> >> >> +       if (ret) {
> >> >> +               pr_err("%s registering with psblk failed (%d)\n",
> >> >> +                               cxt->dev_name, ret);
> >> >> +               goto free_data;
> >> >> +       }
> >> >> +
> >> >> +       pr_info("%s registered as psblk backend\n", cxt->dev_name);
> >> >> +       return;
> >> >> +
> >> >> +free_data:
> >> >> +       kfree(data);
> >> >> +free_stop:
> >> >> +       kfree(stop);
> >> >> +free_cmd:
> >> >> +       kfree(cmd);
> >> >> +free_mrq:
> >> >> +       kfree(mrq);
> >> >> +out:
> >> >> +       return;
> >> >> +}
> >> >> +
> >> >> +void unregister_mmcpstore(void)
> >> >> +{
> >> >> +       struct mmcpstore_context *cxt = &oops_cxt;
> >> >> +
> >> >> +       unregister_pstore_blk(MMC_BLOCK_MAJOR);
> >> >> +       kfree(cxt->mrq->data);
> >> >> +       kfree(cxt->mrq->stop);
> >> >> +       kfree(cxt->mrq->cmd);
> >> >> +       kfree(cxt->mrq);
> >> >> +       cxt->card = NULL;
> >> >> +}
> >> >> diff --git a/include/linux/mmc/core.h b/include/linux/mmc/core.h
> >> >> index 29aa50711626..53840a361b5a 100644
> >> >> --- a/include/linux/mmc/core.h
> >> >> +++ b/include/linux/mmc/core.h
> >> >> @@ -166,6 +166,11 @@ struct mmc_request {
> >> >>
> >> >>  struct mmc_card;
> >> >>
> >> >> +#if IS_ENABLED(CONFIG_MMC_PSTORE)
> >> >> +void mmc_wait_for_pstore_req(struct mmc_host *host, struct
> >> >> +mmc_request *mrq); int mmc_claim_host_async(struct mmc_host
> >> >> +*host); #endif
> >> >> +
> >> >>  void mmc_wait_for_req(struct mmc_host *host, struct mmc_request
> >> >> *mrq);  int mmc_wait_for_cmd(struct mmc_host *host, struct
> >> >mmc_command *cmd,
> >> >>                 int retries);
> >> >> diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h
> >> >> index
> >> >> 01bba36545c5..ba9001498e03 100644
> >> >> --- a/include/linux/mmc/host.h
> >> >> +++ b/include/linux/mmc/host.h
> >> >> @@ -178,6 +178,18 @@ struct mmc_host_ops {
> >> >>
> >> >>         /* Initialize an SD express card, mandatory for MMC_CAP2_SD_EXP.
> >*/
> >> >>         int     (*init_sd_express)(struct mmc_host *host, struct mmc_ios
> >*ios);
> >> >> +
> >> >> +#if IS_ENABLED(CONFIG_MMC_PSTORE)
> >> >> +       /*
> >> >> +        * The following two APIs are introduced to support mmcpstore
> >> >> +        * functionality. Cleanup API to terminate the ongoing and
> >> >> +        * pending requests before a panic write post, and polling API
> >> >> +        * to ensure that write succeeds before the Kernel dies.
> >> >> +        */
> >> >> +       void    (*req_cleanup_pending)(struct mmc_host *host);
> >> >> +       int     (*req_completion_poll)(struct mmc_host *host,
> >> >> +                                      unsigned long timeout);
> >> >> +#endif
> >> >>  };
> >> >>
> >> >>  struct mmc_cqe_ops {
> >> >> --
> >> >> 2.17.1
> >> >>