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Date: Sun, 8 Nov 2020 22:43:29 +0800
From: 廖威雄 <gmpy.liaowx@...il.com>
To: Christoph Hellwig <hch@....de>
Cc: Kees Cook <keescook@...omium.org>,
Anton Vorontsov <anton@...msg.org>,
Colin Cross <ccross@...roid.com>,
Tony Luck <tony.luck@...el.com>,
WeiXiong Liao <liaoweixiong@...winnertech.com>,
linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 8/9] pstore/blk: use the normal block device I/O path
On Fri, Oct 16, 2020 at 11:33 PM Christoph Hellwig <hch@....de> wrote:
>
> Stop poking into block layer internals and just open the block device
> file an use kernel_read and kernel_write on it. Note that this means
> the transformation from name_to_dev_t can't be used anymore, and proper
> block device file names must be used.
>
> Signed-off-by: Christoph Hellwig <hch@....de>
> ---
> fs/pstore/blk.c | 152 +++++++++++++------------------------
> include/linux/pstore_blk.h | 2 +
> init/main.c | 4 +
> 3 files changed, 57 insertions(+), 101 deletions(-)
>
> diff --git a/fs/pstore/blk.c b/fs/pstore/blk.c
> index 0430b190a1df2a..bd4eadfc9bd795 100644
> --- a/fs/pstore/blk.c
> +++ b/fs/pstore/blk.c
> @@ -8,15 +8,13 @@
>
> #include <linux/kernel.h>
> #include <linux/module.h>
> -#include "../../block/blk.h"
> #include <linux/blkdev.h>
> #include <linux/string.h>
> -#include <linux/of.h>
> -#include <linux/of_address.h>
> -#include <linux/platform_device.h>
> #include <linux/pstore_blk.h>
> +#include <linux/fs.h>
> +#include <linux/file.h>
> +#include <linux/init_syscalls.h>
> #include <linux/mount.h>
> -#include <linux/uio.h>
>
> static long kmsg_size = CONFIG_PSTORE_BLK_KMSG_SIZE;
> module_param(kmsg_size, long, 0400);
> @@ -88,7 +86,6 @@ MODULE_PARM_DESC(blkdev, "block device for pstore storage");
> * during the register/unregister functions.
> */
> static DEFINE_MUTEX(pstore_blk_lock);
> -static struct block_device *psblk_bdev;
> static struct pstore_zone_info *pstore_zone_info;
>
> #define check_size(name, alignsize) ({ \
> @@ -185,70 +182,20 @@ void unregister_pstore_device(const struct pstore_zone_ops *ops)
> }
> EXPORT_SYMBOL_GPL(unregister_pstore_device);
>
> +static struct file *psblk_file;
> +
> static ssize_t psblk_generic_blk_read(char *buf, size_t bytes, loff_t pos)
> {
> - struct block_device *bdev = psblk_bdev;
> - struct file file;
> - struct kiocb kiocb;
> - struct iov_iter iter;
> - struct kvec iov = {.iov_base = buf, .iov_len = bytes};
> -
> - if (!bdev)
> - return -ENODEV;
> -
> - memset(&file, 0, sizeof(struct file));
> - file.f_mapping = bdev->bd_inode->i_mapping;
> - file.f_flags = O_DSYNC | __O_SYNC | O_NOATIME;
> - file.f_inode = bdev->bd_inode;
> - file_ra_state_init(&file.f_ra, file.f_mapping);
> -
> - init_sync_kiocb(&kiocb, &file);
> - kiocb.ki_pos = pos;
> - iov_iter_kvec(&iter, READ, &iov, 1, bytes);
> -
> - return generic_file_read_iter(&kiocb, &iter);
> + return kernel_read(psblk_file, buf, bytes, &pos);
> }
>
> static ssize_t psblk_generic_blk_write(const char *buf, size_t bytes,
> loff_t pos)
> {
> - struct block_device *bdev = psblk_bdev;
> - struct iov_iter iter;
> - struct kiocb kiocb;
> - struct file file;
> - ssize_t ret;
> - struct kvec iov = {.iov_base = (void *)buf, .iov_len = bytes};
> -
> - if (!bdev)
> - return -ENODEV;
> -
> /* Console/Ftrace backend may handle buffer until flush dirty zones */
> if (in_interrupt() || irqs_disabled())
> return -EBUSY;
> -
> - memset(&file, 0, sizeof(struct file));
> - file.f_mapping = bdev->bd_inode->i_mapping;
> - file.f_flags = O_DSYNC | __O_SYNC | O_NOATIME;
> - file.f_inode = bdev->bd_inode;
> -
> - init_sync_kiocb(&kiocb, &file);
> - kiocb.ki_pos = pos;
> - iov_iter_kvec(&iter, WRITE, &iov, 1, bytes);
> -
> - inode_lock(bdev->bd_inode);
> - ret = generic_write_checks(&kiocb, &iter);
> - if (ret > 0)
> - ret = generic_perform_write(&file, &iter, pos);
> - inode_unlock(bdev->bd_inode);
> -
> - if (likely(ret > 0)) {
> - const struct file_operations f_op = {.fsync = blkdev_fsync};
> -
> - file.f_op = &f_op;
> - kiocb.ki_pos += ret;
> - ret = generic_write_sync(&kiocb, ret);
> - }
> - return ret;
> + return kernel_write(psblk_file, buf, bytes, &pos);
> }
>
> static const struct pstore_zone_ops pstore_blk_zone_ops = {
> @@ -257,68 +204,71 @@ static const struct pstore_zone_ops pstore_blk_zone_ops = {
> .write = psblk_generic_blk_write,
> };
>
> -static int __init pstore_blk_init(void)
> +static int __init __pstore_blk_init(const char *name)
> {
> - char bdev_name[BDEVNAME_SIZE];
> - struct block_device *bdev;
> - int ret = -ENODEV;
> - fmode_t mode = FMODE_READ | FMODE_WRITE | FMODE_EXCL;
> - sector_t nr_sects;
> -
> + int ret = -EINVAL;
> +
> if (!best_effort || !blkdev[0])
> return 0;
>
> - /* hold bdev exclusively */
> - bdev = blkdev_get_by_path(blkdev, mode, blkdev);
> - if (IS_ERR(bdev)) {
> - dev_t devt;
> -
> - devt = name_to_dev_t(blkdev);
> - if (devt == 0) {
> - pr_err("failed to open '%s'!\n", blkdev);
> - return -ENODEV;
> - }
> - bdev = blkdev_get_by_dev(devt, mode, blkdev);
> - if (IS_ERR(bdev)) {
> - pr_err("failed to open '%s'!\n", blkdev);
> - return PTR_ERR(bdev);
> - }
> + psblk_file = filp_open(name, O_RDWR | O_DSYNC | O_NOATIME | O_EXCL, 0);
> + if (IS_ERR(psblk_file)) {
> + ret = PTR_ERR(psblk_file);
> + pr_err("failed to open '%s': %d!\n", name, ret);
> + goto out;
> }
> -
> - nr_sects = part_nr_sects_read(bdev->bd_part);
> - if (!nr_sects) {
> - pr_err("not enough space for '%s'\n", blkdev);
> - ret = -ENOSPC;
> - goto err_put_bdev;
> + if (!S_ISBLK(file_inode(psblk_file)->i_mode)) {
> + pr_err("'%s' is not block device!\n", blkdev);
> + goto out_fput;
> }
>
> - /* psblk_bdev must be assigned before register to pstore/blk */
> - psblk_bdev = bdev;
> -
> ret = register_pstore_device(&pstore_blk_zone_ops,
> - nr_sects << SECTOR_SHIFT, 0);
> + file_inode(psblk_file)->i_bdev->bd_inode->i_size, 0);
> if (ret)
> - goto err_put_bdev;
> + goto out_fput;
>
> - bdevname(bdev, bdev_name);
> - pr_info("attached %s (no dedicated panic_write!)\n", bdev_name);
> + pr_info("using device '%s'\n", blkdev);
> return 0;
> -
> -err_put_bdev:
> - blkdev_put(bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL);
> - psblk_bdev = NULL;
> +out_fput:
> + fput(psblk_file);
> +out:
> + psblk_file = NULL;
> return ret;
> }
> +
> +#ifdef MODULE
> +static int __init pstore_blk_init(void)
> +{
> + return __pstore_blk_init(blkdev);
> +}
> late_initcall(pstore_blk_init);
>
> static void __exit pstore_blk_exit(void)
> {
> - if (!psblk_bdev)
> + if (!psblk_file)
> return;
> unregister_pstore_device(&pstore_blk_zone_ops);
> - blkdev_put(psblk_bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL);
> + fput(psblk_file);
> }
> module_exit(pstore_blk_exit);
> +#else /* MODULE */
> +/*
> + * During early boot the real root file system hasn't been mounted yet,
> + * and not device nodes are present yet. Use the same scheme to find
> + * the device that we use for mounting the root file system.
> + */
> +void __init pstore_blk_early_init(void)
> +{
> + const char devname[] = "/dev/pstore-blk";
> + dev_t dev = name_to_dev_t(blkdev);
> +
> + if (!dev)
> + return;
> + init_unlink(devname);
> + init_mknod(devname, S_IFBLK | 0600, new_encode_dev(dev));
> + __pstore_blk_init(devname);
How about pstore/blk making /dev/pstore-blk node no matter build-in
or module. Then pstore/blk always opens /dev/pstore-blk. By this way,
blkdev can also be a device number if pstore/blk built as a module.
> +}
> +#endif /* MODULE */
>
> /* get information of pstore/blk */
> int pstore_blk_get_config(struct pstore_blk_config *info)
> diff --git a/include/linux/pstore_blk.h b/include/linux/pstore_blk.h
> index 0abd412a6cb3e3..7c06b9d6740e2a 100644
> --- a/include/linux/pstore_blk.h
> +++ b/include/linux/pstore_blk.h
> @@ -39,4 +39,6 @@ struct pstore_blk_config {
> */
> int pstore_blk_get_config(struct pstore_blk_config *info);
>
> +void __init pstore_blk_early_init(void);
> +
> #endif
> diff --git a/init/main.c b/init/main.c
> index 1af84337cb18d5..058cce64f70390 100644
> --- a/init/main.c
> +++ b/init/main.c
> @@ -98,6 +98,7 @@
> #include <linux/mem_encrypt.h>
> #include <linux/kcsan.h>
> #include <linux/init_syscalls.h>
> +#include <linux/pstore_blk.h>
>
> #include <asm/io.h>
> #include <asm/bugs.h>
> @@ -1524,6 +1525,9 @@ static noinline void __init kernel_init_freeable(void)
> prepare_namespace();
> }
>
> + if (IS_BUILTIN(CONFIG_PSTORE_BLK))
> + pstore_blk_early_init();
> +
> /*
> * Ok, we have completed the initial bootup, and
> * we're essentially up and running. Get rid of the
> --
> 2.28.0
>
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