On Wed, Mar 25, 2020 at 04:54:57PM +0800, WeiXiong Liao wrote:
> pstore/blk is similar to pstore/ram, but dump log to block device
> rather than persistent ram.
> [...]
> +int psblk_register_blkdev(unsigned int major, psblk_panic_write_op panic_write)
> +{
> + struct block_device *bdev;
> + struct psblk_device dev = {0};
> + struct bdev_info *binfo;
> + int ret = -ENODEV;
> + void *holder = blkdev;
> +
> + binfo = psblk_get_bdev_info();
> + if (IS_ERR(binfo))
> + return PTR_ERR(binfo);
> +
> + /* only allow driver matching the @blkdev */
> + if (!binfo->devt || MAJOR(binfo->devt) != major) {
> + pr_debug("invalid major %u (expect %u)\n",
> + major, MAJOR(binfo->devt));
> + return -ENODEV;
> + }
> +
> + /* hold bdev exclusively */
> + bdev = psblk_get_bdev(holder);
> + if (IS_ERR(bdev)) {
> + pr_err("failed to open '%s'!\n", blkdev);
> + return PTR_ERR(bdev);
> + }
> +
> + /* psblk_bdev must be assigned before register to pstore/blk */
> + psblk_bdev = bdev;
> + blkdev_panic_write = panic_write;
> +
> + dev.total_size = psblk_bdev_size(bdev);
> + dev.panic_write = panic_write ? psblk_blk_panic_write : NULL;
> + dev.read = psblk_generic_blk_read;
> + dev.write = psblk_generic_blk_write;
> +
> + ret = psblk_register_do(&dev);
> + if (ret)
> + goto err_put_bdev;
> +
> + pr_info("using '%s'\n", blkdev);
> + return 0;
> +
> +err_put_bdev:
> + psblk_bdev = NULL;
> + blkdev_panic_write = NULL;
> + psblk_put_bdev(bdev, holder);
> + return ret;
> +}
> +EXPORT_SYMBOL_GPL(psblk_register_blkdev);
I've gotten this series refactored on top of current pstore, and I've
been making various bikeshed changes to names, etc, and as I went to go
start testing, I realized that nothing actually uses
psblk_register_blkdev().
It seems like it should be possible to just start using this on any
block device of the user's choosing. I assume the idea is to allow for
drivers to register panic_write handlers, but even without that, it'd be
nice to just be able to test this with something like /dev/loop0.
What's your thinking on how this would happen? It seems like if
pstore/blk uses pstore/zone, and mtdpstore uses pstore/blk, there should
be a blkoops that uses pstore/blk too? I guess I need to learn a bit
more about how block device probing works so pstore/blk can notice
devices as they're brought online, etc.
--
Kees Cook
