Commit 653d7825 authored by Dan Williams's avatar Dan Williams Committed by Andrew Morton
Browse files

dcssblk: mark DAX broken, remove FS_DAX_LIMITED support 

The dcssblk driver has long needed special case supoprt to enable limited
dax operation, so called CONFIG_FS_DAX_LIMITED.  This mode works around
the incomplete support for ZONE_DEVICE on s390 by forgoing the ability of
dax-mapped pages to support GUP.

Now, pending cleanups to fsdax that fix its reference counting [1] depend
on the ability of all dax drivers to supply ZONE_DEVICE pages.

To allow that work to move forward, dax support needs to be paused for
dcssblk until ZONE_DEVICE support arrives.  That work has been known for a
few years [2], and the removal of "pte_devmap" requirements [3] makes the
conversion easier.

For now, place the support behind CONFIG_BROKEN, and remove PFN_SPECIAL
(dcssblk was the only user).

Link: http://lore.kernel.org/cover.9f0e45d52f5cff58807831b6b867084d0b14b61c.1725941415.git-series.apopple@nvidia.com [1]
Link: http://lore.kernel.org/20210820210318.187742e8@thinkpad/ [2]
Link: http://lore.kernel.org/4511465a4f8429f45e2ac70d2e65dc5e1df1eb47.1725941415.git-series.apopple@nvidia.com [3]
Link: https://lkml.kernel.org/r/33eef2379c0d240f40cc15453fad2df1a4ae34c8.1740713401.git-series.apopple@nvidia.com


Signed-off-by: default avatarDan Williams <dan.j.williams@intel.com>
Reviewed-by: default avatarGerald Schaefer <gerald.schaefer@linux.ibm.com>
Tested-by: default avatarAlexander Gordeev <agordeev@linux.ibm.com>
Acked-by: default avatarDavid Hildenbrand <david@redhat.com>
Tested-by: default avatarAlison Schofield <alison.schofield@intel.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Christian Borntraeger <borntraeger@linux.ibm.com>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Asahi Lina <lina@asahilina.net>
Cc: Balbir Singh <balbirs@nvidia.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Chunyan Zhang <zhang.lyra@gmail.com>
Cc: "Darrick J. Wong" <djwong@kernel.org>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Dave Jiang <dave.jiang@intel.com>
Cc: Huacai Chen <chenhuacai@kernel.org>
Cc: Ira Weiny <ira.weiny@intel.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: linmiaohe <linmiaohe@huawei.com>
Cc: Logan Gunthorpe <logang@deltatee.com>
Cc: Michael "Camp Drill Sergeant" Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Ted Ts'o <tytso@mit.edu>
Cc: Vishal Verma <vishal.l.verma@intel.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: WANG Xuerui <kernel@xen0n.name>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent e5cb2325

Documentation/filesystems/dax.rst

+0 −1
Original line number Diff line number Diff line
@@ -207,7 +207,6 @@ implement direct_access. 


These block devices may be used for inspiration:

- brd: RAM backed block device driver

- dcssblk: s390 dcss block device driver

- pmem: NVDIMM persistent memory driver

drivers/s390/block/Kconfig

+10 −2
Original line number Diff line number Diff line
@@ -4,13 +4,21 @@ comment "S/390 block device drivers" 


config DCSSBLK

	def_tristate m

	select FS_DAX_LIMITED

	select DAX

	prompt "DCSSBLK support"

	depends on S390 && BLOCK

	help

	  Support for dcss block device



config DCSSBLK_DAX

	def_bool y

	depends on DCSSBLK

	# requires S390 ZONE_DEVICE support

	depends on BROKEN

	select DAX

	prompt "DCSSBLK DAX support"

	help

	  Enable DAX operation for the dcss block device



config DASD

	def_tristate y

	prompt "Support for DASD devices"

drivers/s390/block/dcssblk.c

+17 −10
Original line number Diff line number Diff line
@@ -534,6 +534,21 @@ static const struct attribute_group *dcssblk_dev_attr_groups[] = { 
	NULL,

};



static int dcssblk_setup_dax(struct dcssblk_dev_info *dev_info)

{

	struct dax_device *dax_dev;



	if (!IS_ENABLED(CONFIG_DCSSBLK_DAX))

		return 0;



	dax_dev = alloc_dax(dev_info, &dcssblk_dax_ops);

	if (IS_ERR(dax_dev))

		return PTR_ERR(dax_dev);

	set_dax_synchronous(dax_dev);

	dev_info->dax_dev = dax_dev;

	return dax_add_host(dev_info->dax_dev, dev_info->gd);

}



/*

 * device attribute for adding devices

 */
@@ -547,7 +562,6 @@ dcssblk_add_store(struct device *dev, struct device_attribute *attr, const char 
	int rc, i, j, num_of_segments;

	struct dcssblk_dev_info *dev_info;

	struct segment_info *seg_info, *temp;

	struct dax_device *dax_dev;

	char *local_buf;

	unsigned long seg_byte_size;
@@ -674,14 +688,7 @@ dcssblk_add_store(struct device *dev, struct device_attribute *attr, const char 
	if (rc)

		goto put_dev;



	dax_dev = alloc_dax(dev_info, &dcssblk_dax_ops);

	if (IS_ERR(dax_dev)) {

		rc = PTR_ERR(dax_dev);

		goto put_dev;

	}

	set_dax_synchronous(dax_dev);

	dev_info->dax_dev = dax_dev;

	rc = dax_add_host(dev_info->dax_dev, dev_info->gd);

	rc = dcssblk_setup_dax(dev_info);

	if (rc)

		goto out_dax;
@@ -917,7 +924,7 @@ __dcssblk_direct_access(struct dcssblk_dev_info *dev_info, pgoff_t pgoff, 
		*kaddr = __va(dev_info->start + offset);

	if (pfn)

		*pfn = __pfn_to_pfn_t(PFN_DOWN(dev_info->start + offset),

				PFN_DEV|PFN_SPECIAL);

				      PFN_DEV);



	return (dev_sz - offset) / PAGE_SIZE;

}