| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <zbvq7pr2v7zkaghxda2d3bnyt64kicyxuwart6jt5cbtm7a2tr@nkursuyanyoe>
Date: Fri, 7 Feb 2025 16:31:47 +1100
From: Alistair Popple <apopple@...dia.com>
To: Dan Williams <dan.j.williams@...el.com>
Cc: akpm@...ux-foundation.org, linux-mm@...ck.org,
alison.schofield@...el.com, lina@...hilina.net, zhang.lyra@...il.com,
gerald.schaefer@...ux.ibm.com, vishal.l.verma@...el.com, dave.jiang@...el.com,
logang@...tatee.com, bhelgaas@...gle.com, jack@...e.cz, jgg@...pe.ca,
catalin.marinas@....com, will@...nel.org, mpe@...erman.id.au, npiggin@...il.com,
dave.hansen@...ux.intel.com, ira.weiny@...el.com, willy@...radead.org, djwong@...nel.org,
tytso@....edu, linmiaohe@...wei.com, david@...hat.com, peterx@...hat.com,
linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org, linuxppc-dev@...ts.ozlabs.org, nvdimm@...ts.linux.dev,
linux-cxl@...r.kernel.org, linux-fsdevel@...r.kernel.org, linux-ext4@...r.kernel.org,
linux-xfs@...r.kernel.org, jhubbard@...dia.com, hch@....de, david@...morbit.com,
chenhuacai@...nel.org, kernel@...0n.name, loongarch@...ts.linux.dev
Subject: Re: [PATCH v6 21/26] fs/dax: Properly refcount fs dax pages
On Mon, Jan 13, 2025 at 07:35:07PM -0800, Dan Williams wrote:
> Alistair Popple wrote:
[...]
> ...and here is that aformentioned patch:
This patch is different from what you originally posted here:
https://yhbt.net/lore/linux-s390/172721874675.497781.3277495908107141898.stgit@dwillia2-xfh.jf.intel.com/
> -- 8< --
> Subject: dcssblk: Mark DAX broken, remove FS_DAX_LIMITED support
>
> From: Dan Williams <dan.j.williams@...el.com>
>
> 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).
Specifically it no longer removes PFN_SPECIAL. Was this intentional? Or should I
really have picked up the original patch from the mailing list?
- Alistair
> 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]
> Reviewed-by: Gerald Schaefer <gerald.schaefer@...ux.ibm.com>
> Tested-by: Alexander Gordeev <agordeev@...ux.ibm.com>
> Acked-by: David Hildenbrand <david@...hat.com>
> Cc: Heiko Carstens <hca@...ux.ibm.com>
> Cc: Vasily Gorbik <gor@...ux.ibm.com>
> Cc: Christian Borntraeger <borntraeger@...ux.ibm.com>
> Cc: Sven Schnelle <svens@...ux.ibm.com>
> Cc: Jan Kara <jack@...e.cz>
> Cc: Matthew Wilcox <willy@...radead.org>
> Cc: Christoph Hellwig <hch@....de>
> Cc: Alistair Popple <apopple@...dia.com>
> Signed-off-by: Dan Williams <dan.j.williams@...el.com>
> ---
> Documentation/filesystems/dax.rst | 1 -
> drivers/s390/block/Kconfig | 12 ++++++++++--
> drivers/s390/block/dcssblk.c | 27 +++++++++++++++++----------
> 3 files changed, 27 insertions(+), 13 deletions(-)
>
> diff --git a/Documentation/filesystems/dax.rst b/Documentation/filesystems/dax.rst
> index 719e90f1988e..08dd5e254cc5 100644
> --- a/Documentation/filesystems/dax.rst
> +++ b/Documentation/filesystems/dax.rst
> @@ -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
>
>
> diff --git a/drivers/s390/block/Kconfig b/drivers/s390/block/Kconfig
> index e3710a762aba..4bfe469c04aa 100644
> --- a/drivers/s390/block/Kconfig
> +++ b/drivers/s390/block/Kconfig
> @@ -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"
> diff --git a/drivers/s390/block/dcssblk.c b/drivers/s390/block/dcssblk.c
> index 0f14d279d30b..7248e547fefb 100644
> --- a/drivers/s390/block/dcssblk.c
> +++ b/drivers/s390/block/dcssblk.c
> @@ -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;
> }
Powered by blists - more mailing lists