[WIP] Linux block device API updates.

[rkitover]

WORK IN PROGRESS PLEASE DO NOT MERGE

In 4e7b5671c6a883d94b5428e1a9c141bbd56cb2a6 Linux makes major changes to
the block device API.

To accommodate this, change the vdev_lookup_bdev() API signature to:

boolean_t vdev_lookup_bdev(const char *path, dev_t *dev);

and handle calling bdput(struct block_device *) for the older variants,
as this is no longer required.

Motivation and Context

Compatibility with linux git master.

#11387

Block dev API changes are in:

torvalds/linux@4e7b567

get_disk_and_module() removed in:

torvalds/linux@4e7b567

Description

There are more problems to fix here, ./configure now works, but the build still fails on errors like:

In file included from /usr/src/zfs/include/os/linux/spl/sys/uio.h:31,
                 from /usr/src/zfs/include/os/linux/spl/sys/sunddi.h:28,
                 from /usr/src/zfs/include/sys/zfs_context.h:69,
                 from /usr/src/zfs/module/zfs/dnode_sync.c:29:
/usr/src/zfs/include/os/linux/kernel/linux/blkdev_compat.h: В функции «get_disk_and_module»:
/usr/src/zfs/include/os/linux/kernel/linux/blkdev_compat.h:106:10: ошибка: неявная декларация функции «get_disk»; имелось в виду «put_disk»? [-Werror=implicit-function-declaration]
  106 |  return (get_disk(disk));
      |          ^~~~~~~~
      |          put_disk

How Has This Been Tested?

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Performance enhancement (non-breaking change which improves efficiency)
• Code cleanup (non-breaking change which makes code smaller or more readable)
• Breaking change (fix or feature that would cause existing functionality to change)
• Library ABI change (libzfs, libzfs_core, libnvpair, libuutil and libzfsbootenv)
• Documentation (a change to man pages or other documentation)

Checklist:

• My code follows the OpenZFS code style requirements.
• I have updated the documentation accordingly.
• I have read the contributing document.
• I have added tests to cover my changes.
• I have run the ZFS Test Suite with this change applied.
• All commit messages are properly formatted and contain Signed-off-by.

[behlendorf]

@rkitover thanks for taking a look at this. As it turns out I gave sorting this mess out a try myself and opened #11390. I'd have probably held off if I knew you were already working on it. Since you've already started taking a look at this code would you mind reviewing my proposed changes.

[rkitover]

Absolutely, looking now.

[behlendorf]

Thanks. I just refreshed it to resolve two build failures on some earlier kernels (4.4) with the IO accounting changes.

[rkitover]

Closing, superseded by #11390.