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    SubjectRe: [PATCH 3/9] pstore/blk: remove {un,}register_pstore_blk
    On Fri, Oct 16, 2020 at 03:20:41PM +0200, Christoph Hellwig wrote:
    > This interface is entirely unused, so remove them and various bits of
    > unreachable code.

    Yeah, this is fair to remove -- there are no users. I'm not a fan of
    dropping it, but it can come back if anyone wants to provide a full
    generic block device implementation.

    Reviewed-by: Kees Cook <keescook@chromium.org>


    >
    > Signed-off-by: Christoph Hellwig <hch@lst.de>
    > ---
    > Documentation/admin-guide/pstore-blk.rst | 8 +--
    > fs/pstore/blk.c | 79 ++----------------------
    > include/linux/pstore_blk.h | 42 -------------
    > 3 files changed, 7 insertions(+), 122 deletions(-)
    >
    > diff --git a/Documentation/admin-guide/pstore-blk.rst b/Documentation/admin-guide/pstore-blk.rst
    > index d9ec8b0572d3b2..84477621384d85 100644
    > --- a/Documentation/admin-guide/pstore-blk.rst
    > +++ b/Documentation/admin-guide/pstore-blk.rst
    > @@ -151,13 +151,7 @@ otherwise KMSG_DUMP_MAX.
    > Configurations for driver
    > -------------------------
    >
    > -Only a block device driver cares about these configurations. A block device
    > -driver uses ``register_pstore_blk`` to register to pstore/blk.
    > -
    > -.. kernel-doc:: fs/pstore/blk.c
    > - :identifiers: register_pstore_blk
    > -
    > -A non-block device driver uses ``register_pstore_device`` with
    > +A device driver uses ``register_pstore_device`` with
    > ``struct pstore_device_info`` to register to pstore/blk.
    >
    > .. kernel-doc:: fs/pstore/blk.c
    > diff --git a/fs/pstore/blk.c b/fs/pstore/blk.c
    > index fcd5563dde063c..7f8368e94b3604 100644
    > --- a/fs/pstore/blk.c
    > +++ b/fs/pstore/blk.c
    > @@ -90,7 +90,6 @@ MODULE_PARM_DESC(blkdev, "block device for pstore storage");
    > static DEFINE_MUTEX(pstore_blk_lock);
    > static struct block_device *psblk_bdev;
    > static struct pstore_zone_info *pstore_zone_info;
    > -static pstore_blk_panic_write_op blkdev_panic_write;
    >
    > struct bdev_info {
    > dev_t devt;
    > @@ -341,24 +340,7 @@ static ssize_t psblk_generic_blk_write(const char *buf, size_t bytes,
    > return ret;
    > }
    >
    > -static ssize_t psblk_blk_panic_write(const char *buf, size_t size,
    > - loff_t off)
    > -{
    > - int ret;
    > -
    > - if (!blkdev_panic_write)
    > - return -EOPNOTSUPP;
    > -
    > - /* size and off must align to SECTOR_SIZE for block device */
    > - ret = blkdev_panic_write(buf, off >> SECTOR_SHIFT,
    > - size >> SECTOR_SHIFT);
    > - /* try next zone */
    > - if (ret == -ENOMSG)
    > - return ret;
    > - return ret ? -EIO : size;
    > -}
    > -
    > -static int __register_pstore_blk(struct pstore_blk_info *info)
    > +static int __register_pstore_blk(void)
    > {
    > char bdev_name[BDEVNAME_SIZE];
    > struct block_device *bdev;
    > @@ -378,68 +360,34 @@ static int __register_pstore_blk(struct pstore_blk_info *info)
    > }
    >
    > /* only allow driver matching the @blkdev */
    > - if (!binfo.devt || (!best_effort &&
    > - MAJOR(binfo.devt) != info->major)) {
    > - pr_debug("invalid major %u (expect %u)\n",
    > - info->major, MAJOR(binfo.devt));
    > + if (!binfo.devt) {
    > + pr_debug("no major\n");
    > ret = -ENODEV;
    > goto err_put_bdev;
    > }
    >
    > /* psblk_bdev must be assigned before register to pstore/blk */
    > psblk_bdev = bdev;
    > - blkdev_panic_write = info->panic_write;
    > -
    > - /* Copy back block device details. */
    > - info->devt = binfo.devt;
    > - info->nr_sects = binfo.nr_sects;
    > - info->start_sect = binfo.start_sect;
    >
    > memset(&dev, 0, sizeof(dev));
    > - dev.total_size = info->nr_sects << SECTOR_SHIFT;
    > - dev.flags = info->flags;
    > + dev.total_size = binfo.nr_sects << SECTOR_SHIFT;
    > dev.read = psblk_generic_blk_read;
    > dev.write = psblk_generic_blk_write;
    > - dev.erase = NULL;
    > - dev.panic_write = info->panic_write ? psblk_blk_panic_write : NULL;
    >
    > ret = __register_pstore_device(&dev);
    > if (ret)
    > goto err_put_bdev;
    >
    > bdevname(bdev, bdev_name);
    > - pr_info("attached %s%s\n", bdev_name,
    > - info->panic_write ? "" : " (no dedicated panic_write!)");
    > + pr_info("attached %s (no dedicated panic_write!)\n", bdev_name);
    > return 0;
    >
    > err_put_bdev:
    > psblk_bdev = NULL;
    > - blkdev_panic_write = NULL;
    > psblk_put_bdev(bdev, holder);
    > return ret;
    > }
    >
    > -/**
    > - * register_pstore_blk() - register block device to pstore/blk
    > - *
    > - * @info: details on the desired block device interface
    > - *
    > - * Return:
    > - * * 0 - OK
    > - * * Others - something error.
    > - */
    > -int register_pstore_blk(struct pstore_blk_info *info)
    > -{
    > - int ret;
    > -
    > - mutex_lock(&pstore_blk_lock);
    > - ret = __register_pstore_blk(info);
    > - mutex_unlock(&pstore_blk_lock);
    > -
    > - return ret;
    > -}
    > -EXPORT_SYMBOL_GPL(register_pstore_blk);
    > -
    > static void __unregister_pstore_blk(unsigned int major)
    > {
    > struct pstore_device_info dev = { .read = psblk_generic_blk_read };
    > @@ -449,24 +397,10 @@ static void __unregister_pstore_blk(unsigned int major)
    > if (psblk_bdev && MAJOR(psblk_bdev->bd_dev) == major) {
    > __unregister_pstore_device(&dev);
    > psblk_put_bdev(psblk_bdev, holder);
    > - blkdev_panic_write = NULL;
    > psblk_bdev = NULL;
    > }
    > }
    >
    > -/**
    > - * unregister_pstore_blk() - unregister block device from pstore/blk
    > - *
    > - * @major: the major device number of device
    > - */
    > -void unregister_pstore_blk(unsigned int major)
    > -{
    > - mutex_lock(&pstore_blk_lock);
    > - __unregister_pstore_blk(major);
    > - mutex_unlock(&pstore_blk_lock);
    > -}
    > -EXPORT_SYMBOL_GPL(unregister_pstore_blk);
    > -
    > /* get information of pstore/blk */
    > int pstore_blk_get_config(struct pstore_blk_config *info)
    > {
    > @@ -483,12 +417,11 @@ EXPORT_SYMBOL_GPL(pstore_blk_get_config);
    >
    > static int __init pstore_blk_init(void)
    > {
    > - struct pstore_blk_info info = { };
    > int ret = 0;
    >
    > mutex_lock(&pstore_blk_lock);
    > if (!pstore_zone_info && best_effort && blkdev[0])
    > - ret = __register_pstore_blk(&info);
    > + ret = __register_pstore_blk();
    > mutex_unlock(&pstore_blk_lock);
    >
    > return ret;
    > diff --git a/include/linux/pstore_blk.h b/include/linux/pstore_blk.h
    > index 61e914522b0193..99564f93d77488 100644
    > --- a/include/linux/pstore_blk.h
    > +++ b/include/linux/pstore_blk.h
    > @@ -7,48 +7,6 @@
    > #include <linux/pstore.h>
    > #include <linux/pstore_zone.h>
    >
    > -/**
    > - * typedef pstore_blk_panic_write_op - panic write operation to block device
    > - *
    > - * @buf: the data to write
    > - * @start_sect: start sector to block device
    > - * @sects: sectors count on buf
    > - *
    > - * Return: On success, zero should be returned. Others excluding -ENOMSG
    > - * mean error. -ENOMSG means to try next zone.
    > - *
    > - * Panic write to block device must be aligned to SECTOR_SIZE.
    > - */
    > -typedef int (*pstore_blk_panic_write_op)(const char *buf, sector_t start_sect,
    > - sector_t sects);
    > -
    > -/**
    > - * struct pstore_blk_info - pstore/blk registration details
    > - *
    > - * @major: Which major device number to support with pstore/blk
    > - * @flags: The supported PSTORE_FLAGS_* from linux/pstore.h.
    > - * @panic_write:The write operation only used for the panic case.
    > - * This can be NULL, but is recommended to avoid losing
    > - * crash data if the kernel's IO path or work queues are
    > - * broken during a panic.
    > - * @devt: The dev_t that pstore/blk has attached to.
    > - * @nr_sects: Number of sectors on @devt.
    > - * @start_sect: Starting sector on @devt.
    > - */
    > -struct pstore_blk_info {
    > - unsigned int major;
    > - unsigned int flags;
    > - pstore_blk_panic_write_op panic_write;
    > -
    > - /* Filled in by pstore/blk after registration. */
    > - dev_t devt;
    > - sector_t nr_sects;
    > - sector_t start_sect;
    > -};
    > -
    > -int register_pstore_blk(struct pstore_blk_info *info);
    > -void unregister_pstore_blk(unsigned int major);
    > -
    > /**
    > * struct pstore_device_info - back-end pstore/blk driver structure.
    > *
    > --
    > 2.28.0
    >

    --
    Kees Cook

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