On Tue, Jul 14 2020, Christoph Hellwig wrote:

> md_setup_drive knows it works with md devices, so it is rather pointless
> to open a file descriptor and issue ioctls.  Just call directly into the
> relevant low-level md routines after getting a handle to the device using
> blkdev_get_by_dev instead.
>
> Signed-off-by: Christoph Hellwig <h...@lst.de>
> Acked-by: Song Liu <s...@kernel.org>
> ---
>  drivers/md/md-autodetect.c | 127 ++++++++++++++++---------------------
>  drivers/md/md.c            |  20 +++---
>  drivers/md/md.h            |   6 ++
>  3 files changed, 71 insertions(+), 82 deletions(-)
>
> diff --git a/drivers/md/md-autodetect.c b/drivers/md/md-autodetect.c
> index a43a8f1580584c..5b24b5616d3acc 100644
> --- a/drivers/md/md-autodetect.c
> +++ b/drivers/md/md-autodetect.c
> @@ -2,7 +2,6 @@
>  #include <linux/kernel.h>
>  #include <linux/blkdev.h>
>  #include <linux/init.h>
> -#include <linux/syscalls.h>
>  #include <linux/mount.h>
>  #include <linux/major.h>
>  #include <linux/delay.h>
> @@ -120,37 +119,29 @@ static int __init md_setup(char *str)
>       return 1;
>  }
>  
> -static inline int create_dev(char *name, dev_t dev)
> -{
> -     ksys_unlink(name);
> -     return ksys_mknod(name, S_IFBLK|0600, new_encode_dev(dev));
> -}
> -
>  static void __init md_setup_drive(struct md_setup_args *args)
>  {
> -     int minor, i, partitioned;
> -     dev_t dev;
> -     dev_t devices[MD_SB_DISKS+1];
> -     int fd;
> -     int err = 0;
> -     char *devname;
> -     mdu_disk_info_t dinfo;
> +     char *devname = args->device_names;
> +     dev_t devices[MD_SB_DISKS + 1], mdev;
> +     struct mdu_array_info_s ainfo = { };
> +     struct block_device *bdev;
> +     struct mddev *mddev;
> +     int err = 0, i;
>       char name[16];
>  
> -     minor = args->minor;
> -     partitioned = args->partitioned;
> -     devname = args->device_names;
> +     if (args->partitioned) {
> +             mdev = MKDEV(mdp_major, args->minor << MdpMinorShift);
> +             sprintf(name, "md_d%d", args->minor);
> +     } else {
> +             mdev = MKDEV(MD_MAJOR, args->minor);
> +             sprintf(name, "md%d", args->minor);
> +     }
>  
> -     sprintf(name, "/dev/md%s%d", partitioned?"_d":"", minor);
> -     if (partitioned)
> -             dev = MKDEV(mdp_major, minor << MdpMinorShift);
> -     else
> -             dev = MKDEV(MD_MAJOR, minor);
> -     create_dev(name, dev);
>       for (i = 0; i < MD_SB_DISKS && devname != NULL; i++) {
>               struct kstat stat;
>               char *p;
>               char comp_name[64];
> +             dev_t dev;
>  
>               p = strchr(devname, ',');
>               if (p)
> @@ -163,7 +154,7 @@ static void __init md_setup_drive(struct md_setup_args 
> *args)
>               if (vfs_stat(comp_name, &stat) == 0 && S_ISBLK(stat.mode))
>                       dev = new_decode_dev(stat.rdev);
>               if (!dev) {
> -                     printk(KERN_WARNING "md: Unknown device name: %s\n", 
> devname);
> +                     pr_warn("md: Unknown device name: %s\n", devname);
>                       break;
>               }
>  
> @@ -175,68 +166,64 @@ static void __init md_setup_drive(struct md_setup_args 
> *args)
>       if (!i)
>               return;
>  
> -     printk(KERN_INFO "md: Loading md%s%d: %s\n",
> -             partitioned ? "_d" : "", minor,
> -             args->device_names);
> +     pr_info("md: Loading %s: %s\n", name, args->device_names);
>  
> -     fd = ksys_open(name, 0, 0);
> -     if (fd < 0) {
> -             printk(KERN_ERR "md: open failed - cannot start "
> -                             "array %s\n", name);
> +     bdev = blkdev_get_by_dev(mdev, FMODE_READ, NULL);
> +     if (IS_ERR(bdev)) {
> +             pr_err("md: open failed - cannot start array %s\n", name);
>               return;
>       }
> -     if (ksys_ioctl(fd, SET_ARRAY_INFO, 0) == -EBUSY) {
> -             printk(KERN_WARNING
> -                    "md: Ignoring md=%d, already autodetected. (Use 
> raid=noautodetect)\n",
> -                    minor);
> -             ksys_close(fd);
> -             return;

I'd be more comfortable if you added something like
        if (WARN(bdev->bd_disk->fops != md_fops,
                 "Opening block device %x resulted in non-md device\"))
                return;
here.  However even without that

Reviewed-by: NeilBrown <ne...@suse.de>

Thanks,
NeilBrown


> +     mddev = bdev->bd_disk->private_data;
> +
> +     err = mddev_lock(mddev);
> +     if (err) {
> +             pr_err("md: failed to lock array %s\n", name);
> +             goto out_blkdev_put;
> +     }
> +
> +     if (!list_empty(&mddev->disks) || mddev->raid_disks) {
> +             pr_warn("md: Ignoring %s, already autodetected. (Use 
> raid=noautodetect)\n",
> +                    name);
> +             goto out_unlock;
>       }
>  
>       if (args->level != LEVEL_NONE) {
>               /* non-persistent */
> -             mdu_array_info_t ainfo;
>               ainfo.level = args->level;
> -             ainfo.size = 0;
> -             ainfo.nr_disks =0;
> -             ainfo.raid_disks =0;
> -             while (devices[ainfo.raid_disks])
> -                     ainfo.raid_disks++;
> -             ainfo.md_minor =minor;
> +             ainfo.md_minor = args->minor;
>               ainfo.not_persistent = 1;
> -
>               ainfo.state = (1 << MD_SB_CLEAN);
> -             ainfo.layout = 0;
>               ainfo.chunk_size = args->chunk;
> -             err = ksys_ioctl(fd, SET_ARRAY_INFO, (long)&ainfo);
> -             for (i = 0; !err && i <= MD_SB_DISKS; i++) {
> -                     dev = devices[i];
> -                     if (!dev)
> -                             break;
> +             while (devices[ainfo.raid_disks])
> +                     ainfo.raid_disks++;
> +     }
> +
> +     err = md_set_array_info(mddev, &ainfo);
> +
> +     for (i = 0; i <= MD_SB_DISKS && devices[i]; i++) {
> +             struct mdu_disk_info_s dinfo = {
> +                     .major  = MAJOR(devices[i]),
> +                     .minor  = MINOR(devices[i]),
> +             };
> +
> +             if (args->level != LEVEL_NONE) {
>                       dinfo.number = i;
>                       dinfo.raid_disk = i;
> -                     dinfo.state = (1<<MD_DISK_ACTIVE)|(1<<MD_DISK_SYNC);
> -                     dinfo.major = MAJOR(dev);
> -                     dinfo.minor = MINOR(dev);
> -                     err = ksys_ioctl(fd, ADD_NEW_DISK,
> -                                      (long)&dinfo);
> -             }
> -     } else {
> -             /* persistent */
> -             for (i = 0; i <= MD_SB_DISKS; i++) {
> -                     dev = devices[i];
> -                     if (!dev)
> -                             break;
> -                     dinfo.major = MAJOR(dev);
> -                     dinfo.minor = MINOR(dev);
> -                     ksys_ioctl(fd, ADD_NEW_DISK, (long)&dinfo);
> +                     dinfo.state =
> +                             (1 << MD_DISK_ACTIVE) | (1 << MD_DISK_SYNC);
>               }
> +
> +             md_add_new_disk(mddev, &dinfo);
>       }
> +
>       if (!err)
> -             err = ksys_ioctl(fd, RUN_ARRAY, 0);
> +             err = do_md_run(mddev);
>       if (err)
> -             printk(KERN_WARNING "md: starting md%d failed\n", minor);
> -     ksys_close(fd);
> +             pr_warn("md: starting %s failed\n", name);
> +out_unlock:
> +     mddev_unlock(mddev);
> +out_blkdev_put:
> +     blkdev_put(bdev, FMODE_READ);
>  }
>  
>  static int __init raid_setup(char *str)
> @@ -286,8 +273,6 @@ void __init md_run_setup(void)
>  {
>       int ent;
>  
> -     create_dev("/dev/md0", MKDEV(MD_MAJOR, 0));
> -
>       if (raid_noautodetect)
>               printk(KERN_INFO "md: Skipping autodetection of RAID arrays. 
> (raid=autodetect will force)\n");
>       else
> diff --git a/drivers/md/md.c b/drivers/md/md.c
> index 6e9a48da474848..9960cfeb59a50c 100644
> --- a/drivers/md/md.c
> +++ b/drivers/md/md.c
> @@ -4368,7 +4368,6 @@ array_state_show(struct mddev *mddev, char *page)
>  
>  static int do_md_stop(struct mddev *mddev, int ro, struct block_device 
> *bdev);
>  static int md_set_readonly(struct mddev *mddev, struct block_device *bdev);
> -static int do_md_run(struct mddev *mddev);
>  static int restart_array(struct mddev *mddev);
>  
>  static ssize_t
> @@ -6015,7 +6014,7 @@ int md_run(struct mddev *mddev)
>  }
>  EXPORT_SYMBOL_GPL(md_run);
>  
> -static int do_md_run(struct mddev *mddev)
> +int do_md_run(struct mddev *mddev)
>  {
>       int err;
>  
> @@ -6651,7 +6650,7 @@ static int get_disk_info(struct mddev *mddev, void 
> __user * arg)
>       return 0;
>  }
>  
> -static int add_new_disk(struct mddev *mddev, mdu_disk_info_t *info)
> +int md_add_new_disk(struct mddev *mddev, struct mdu_disk_info_s *info)
>  {
>       char b[BDEVNAME_SIZE], b2[BDEVNAME_SIZE];
>       struct md_rdev *rdev;
> @@ -6697,7 +6696,7 @@ static int add_new_disk(struct mddev *mddev, 
> mdu_disk_info_t *info)
>       }
>  
>       /*
> -      * add_new_disk can be used once the array is assembled
> +      * md_add_new_disk can be used once the array is assembled
>        * to add "hot spares".  They must already have a superblock
>        * written
>        */
> @@ -6810,7 +6809,7 @@ static int add_new_disk(struct mddev *mddev, 
> mdu_disk_info_t *info)
>               return err;
>       }
>  
> -     /* otherwise, add_new_disk is only allowed
> +     /* otherwise, md_add_new_disk is only allowed
>        * for major_version==0 superblocks
>        */
>       if (mddev->major_version != 0) {
> @@ -7055,7 +7054,7 @@ static int set_bitmap_file(struct mddev *mddev, int fd)
>  }
>  
>  /*
> - * set_array_info is used two different ways
> + * md_set_array_info is used two different ways
>   * The original usage is when creating a new array.
>   * In this usage, raid_disks is > 0 and it together with
>   *  level, size, not_persistent,layout,chunksize determine the
> @@ -7067,9 +7066,8 @@ static int set_bitmap_file(struct mddev *mddev, int fd)
>   *  The minor and patch _version numbers are also kept incase the
>   *  super_block handler wishes to interpret them.
>   */
> -static int set_array_info(struct mddev *mddev, mdu_array_info_t *info)
> +int md_set_array_info(struct mddev *mddev, struct mdu_array_info_s *info)
>  {
> -
>       if (info->raid_disks == 0) {
>               /* just setting version number for superblock loading */
>               if (info->major_version < 0 ||
> @@ -7560,7 +7558,7 @@ static int md_ioctl(struct block_device *bdev, fmode_t 
> mode,
>                       err = -EBUSY;
>                       goto unlock;
>               }
> -             err = set_array_info(mddev, &info);
> +             err = md_set_array_info(mddev, &info);
>               if (err) {
>                       pr_warn("md: couldn't set array info. %d\n", err);
>                       goto unlock;
> @@ -7614,7 +7612,7 @@ static int md_ioctl(struct block_device *bdev, fmode_t 
> mode,
>                               /* Need to clear read-only for this */
>                               break;
>                       else
> -                             err = add_new_disk(mddev, &info);
> +                             err = md_add_new_disk(mddev, &info);
>                       goto unlock;
>               }
>               break;
> @@ -7682,7 +7680,7 @@ static int md_ioctl(struct block_device *bdev, fmode_t 
> mode,
>               if (copy_from_user(&info, argp, sizeof(info)))
>                       err = -EFAULT;
>               else
> -                     err = add_new_disk(mddev, &info);
> +                     err = md_add_new_disk(mddev, &info);
>               goto unlock;
>       }
>  
> diff --git a/drivers/md/md.h b/drivers/md/md.h
> index 6f8fff77ce10a5..7ee81aa2eac862 100644
> --- a/drivers/md/md.h
> +++ b/drivers/md/md.h
> @@ -801,7 +801,13 @@ static inline void mddev_check_write_zeroes(struct mddev 
> *mddev, struct bio *bio
>               mddev->queue->limits.max_write_zeroes_sectors = 0;
>  }
>  
> +struct mdu_array_info_s;
> +struct mdu_disk_info_s;
> +
>  extern int mdp_major;
>  void md_autostart_arrays(int part);
> +int md_set_array_info(struct mddev *mddev, struct mdu_array_info_s *info);
> +int md_add_new_disk(struct mddev *mddev, struct mdu_disk_info_s *info);
> +int do_md_run(struct mddev *mddev);
>  
>  #endif /* _MD_MD_H */
> -- 
> 2.27.0

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