Re: [PATCH 08/10] md: Implement ->corrupted_range()

Jan Kara
2021-01-06T17:15:34Z

On Thu 31-12-20 00:55:59, Shiyang Ruan wrote:
> With the support of ->rmap(), it is possible to obtain the superblock on
> a mapped device.
>
> If a pmem device is used as one target of mapped device, we cannot
> obtain its superblock directly. With the help of SYSFS, the mapped
> device can be found on the target devices. So, we iterate the
> bdev->bd_holder_disks to obtain its mapped device.
>
> Signed-off-by: Shiyang Ruan <ruansy.fnst@cn.fujitsu.com>

Thanks for the patch. Two comments below.

> diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
> index 4688bff19c20..9f9a2f3bf73b 100644
> --- a/drivers/nvdimm/pmem.c
> +++ b/drivers/nvdimm/pmem.c
> @@ -256,21 +256,16 @@ static int pmem_rw_page(struct block_device *bdev, sector_t sector,
> static int pmem_corrupted_range(struct gendisk *disk, struct block_device *bdev,
> loff_t disk_offset, size_t len, void *data)
> {
> - struct super_block *sb;
> loff_t bdev_offset;
> sector_t disk_sector = disk_offset >> SECTOR_SHIFT;
> - int rc = 0;
> + int rc = -ENODEV;
>
> bdev = bdget_disk_sector(disk, disk_sector);
> if (!bdev)
> - return -ENODEV;
> + return rc;
>
> bdev_offset = (disk_sector - get_start_sect(bdev)) << SECTOR_SHIFT;
> - sb = get_super(bdev);
> - if (sb && sb->s_op->corrupted_range) {
> - rc = sb->s_op->corrupted_range(sb, bdev, bdev_offset, len, data);
> - drop_super(sb);
> - }
> + rc = bd_corrupted_range(bdev, bdev_offset, bdev_offset, len, data);
>
> bdput(bdev);
> return rc;

This (and the fs/block_dev.c change below) is just refining the function
you've implemented in the patch 6. I think it's confusing to split changes
like this - why not implement things correctly from the start in patch 6?

> diff --git a/fs/block_dev.c b/fs/block_dev.c
> index 9e84b1928b94..0e50f0e8e8af 100644
> --- a/fs/block_dev.c
> +++ b/fs/block_dev.c
> @@ -1171,6 +1171,27 @@ struct bd_holder_disk {
> int refcnt;
> };
>
> +static int bd_disk_holder_corrupted_range(struct block_device *bdev, loff_t off,
> + size_t len, void *data)
> +{
> + struct bd_holder_disk *holder;
> + struct gendisk *disk;
> + int rc = 0;
> +
> + if (list_empty(&(bdev->bd_holder_disks)))
> + return -ENODEV;

This will not compile for !CONFIG_SYSFS kernels. Not that it would be
common but still. Also I'm not sure whether using bd_holder_disks like this
is really the right thing to do (when it seems to be only a sysfs thing),
although admittedly I'm not aware of a better way of getting this
information.

Honza

> +
> + list_for_each_entry(holder, &bdev->bd_holder_disks, list) {
> + disk = holder->disk;
> + if (disk->fops->corrupted_range) {
> + rc = disk->fops->corrupted_range(disk, bdev, off, len, data);
> + if (rc != -ENODEV)
> + break;
> + }
> + }
> + return rc;
> +}
> +
> static struct bd_holder_disk *bd_find_holder_disk(struct block_device *bdev,
> struct gendisk *disk)
> {
> @@ -1378,6 +1399,22 @@ void bd_set_nr_sectors(struct block_device *bdev, sector_t sectors)
> }
> EXPORT_SYMBOL(bd_set_nr_sectors);
>
> +int bd_corrupted_range(struct block_device *bdev, loff_t disk_off, loff_t bdev_off, size_t len, void *data)
> +{
> + struct super_block *sb = get_super(bdev);
> + int rc = 0;
> +
> + if (!sb) {
> + rc = bd_disk_holder_corrupted_range(bdev, disk_off, len, data);
> + return rc;
> + } else if (sb->s_op->corrupted_range)
> + rc = sb->s_op->corrupted_range(sb, bdev, bdev_off, len, data);
> + drop_super(sb);
> +
> + return rc;
> +}
> +EXPORT_SYMBOL(bd_corrupted_range);
> +
> static void __blkdev_put(struct block_device *bdev, fmode_t mode, int for_part);
>
> int bdev_disk_changed(struct block_device *bdev, bool invalidate)
> diff --git a/include/linux/genhd.h b/include/linux/genhd.h
> index ed06209008b8..42290470810d 100644
> --- a/include/linux/genhd.h
> +++ b/include/linux/genhd.h
> @@ -376,6 +376,8 @@ void revalidate_disk_size(struct gendisk *disk, bool verbose);
> bool bdev_check_media_change(struct block_device *bdev);
> int __invalidate_device(struct block_device *bdev, bool kill_dirty);
> void bd_set_nr_sectors(struct block_device *bdev, sector_t sectors);
> +int bd_corrupted_range(struct block_device *bdev, loff_t disk_off,
> + loff_t bdev_off, size_t len, void *data);
>
> /* for drivers/char/raw.c: */
> int blkdev_ioctl(struct block_device *, fmode_t, unsigned, unsigned long);
> --
> 2.29.2
>
>
>
--
Jan Kara <jack@suse.com>
SUSE Labs, CR