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Date: Fri, 21 Apr 2017 18:06:00 -0700
From: Dan Williams <dan.j.williams@...el.com>
To: "linux-nvdimm@...ts.01.org" <linux-nvdimm@...ts.01.org>
Cc: Tony Luck <tony.luck@...el.com>, Jan Kara <jack@...e.cz>,
Mike Snitzer <snitzer@...hat.com>,
Toshi Kani <toshi.kani@....com>,
Matthew Wilcox <mawilcox@...rosoft.com>,
X86 ML <x86@...nel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Christoph Hellwig <hch@....de>, linux-block@...r.kernel.org,
Jeff Moyer <jmoyer@...hat.com>, Ingo Molnar <mingo@...hat.com>,
"Oliver O'Halloran" <oohall@...il.com>,
Al Viro <viro@...iv.linux.org.uk>,
"H. Peter Anvin" <hpa@...or.com>,
linux-fsdevel <linux-fsdevel@...r.kernel.org>,
Ross Zwisler <ross.zwisler@...ux.intel.com>,
dm-devel@...hat.com,
Linus Torvalds <torvalds@...ux-foundation.org>,
Thomas Gleixner <tglx@...utronix.de>,
Gerald Schaefer <gerald.schaefer@...ibm.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Stephen Rothwell <sfr@...b.auug.org.au>,
Jens Axboe <axboe@...com>
Subject: Re: [resend PATCH v2 00/33] dax: introduce dax_operations
[ adding akpm, sfr, and jens ]
I applied this series and pushed it out for the nvdimm.git branch that
gets auto pulled into -next. The set is still awaiting acks from
device-mapper, ext4, xfs, and vfs (for the copy_from_iter_ops, patch
29/33). If those come next week perhaps this can be merged for 4.12,
but if not this will need to wait until 4.13.
There are some minor collisions with Al's copy_from_user rework, the
new dax tracepoints, and the removal of discard support from the brd
driver. A sample merge is available here:
https://git.kernel.org/pub/scm/linux/kernel/git/nvdimm/nvdimm.git/log/?h=libnvdimm-for-4.12-merge
If it causes any other problems just drop and I'll retry for 4.13.
On Mon, Apr 17, 2017 at 12:08 PM, Dan Williams <dan.j.williams@...el.com> wrote:
> [ resend to add dm-devel, linux-block, and fs-devel, apologies for the
> duplicates ]
>
> Changes since v1 [1] and the dax-fs RFC [2]:
> * rename struct dax_inode to struct dax_device (Christoph)
> * rewrite arch_memcpy_to_pmem() in C with inline asm
> * use QUEUE_FLAG_WC to gate dax cache management (Jeff)
> * add device-mapper plumbing for the ->copy_from_iter() and ->flush()
> dax_operations
> * kill struct blk_dax_ctl and bdev_direct_access (Christoph)
> * cleanup the ->direct_access() calling convention to be page based
> (Christoph)
> * introduce dax_get_by_host() and don't pollute struct super_block with
> dax_device details (Christoph)
>
> [1]: https://lists.01.org/pipermail/linux-nvdimm/2017-January/008586.html
> [2]: https://lwn.net/Articles/713064/
>
> ---
> A few months back, in the course of reviewing the memcpy_nocache()
> proposal from Brian, Linus proposed that the pmem specific
> memcpy_to_pmem() routine be moved to be implemented at the driver level
> [3]:
>
> "Quite frankly, the whole 'memcpy_nocache()' idea or (ab-)using
> copy_user_nocache() just needs to die. It's idiotic.
>
> As you point out, it's also fundamentally buggy crap.
>
> Throw it away. There is no possible way this is ever valid or
> portable. We're not going to lie and claim that it is.
>
> If some driver ends up using 'movnt' by hand, that is up to that
> *driver*. But no way in hell should we care about this one whit in
> the sense of <linux/uaccess.h>."
>
> This feedback also dovetails with another fs/dax.c design wart of being
> hard coded to assume the backing device is pmem. We call the pmem
> specific copy, clear, and flush routines even if the backing device
> driver is one of the other 3 dax drivers (axonram, dccssblk, or brd).
> There is no reason to spend cpu cycles flushing the cache after writing
> to brd, for example, since it is using volatile memory for storage.
>
> Moreover, the pmem driver might be fronting a volatile memory range
> published by the ACPI NFIT, or the platform might have arranged to flush
> cpu caches on power fail. This latter capability is a feature that has
> appeared in embedded storage appliances (pre-ACPI-NFIT nvdimm
> platforms).
>
> So, this series:
>
> 1/ moves what was previously named "the pmem api" out of the global
> namespace and into drivers that need to be concerned with
> architecture specific persistent memory considerations.
>
> 2/ arranges for dax to stop abusing __copy_user_nocache() and implements
> a libnvdimm-local memcpy that uses 'movnt' on x86_64. This might be
> expanded in the future to use 'movntdqa' if the copy size is above
> some threshold, or expanded with support for other architectures [4].
>
> 3/ makes cache maintenance optional by arranging for dax to call driver
> specific copy and flush operations only if the driver publishes them.
>
> 4/ allows filesytem-dax cache management to be controlled by the block
> device write-cache queue flag. The pmem driver is updated to clear
> that flag by default when pmem is driving volatile memory.
>
> [3]: https://lists.01.org/pipermail/linux-nvdimm/2017-January/008364.html
> [4]: https://lists.01.org/pipermail/linux-nvdimm/2017-April/009478.html
>
> These patches have been through a round of build regression fixes
> notified by the 0day robot. All review welcome, but the patches that
> need extra attention are the device-mapper and uio changes
> (copy_from_iter_ops).
>
> This series is based on a merge of char-misc-next (for cdev api reworks)
> and libnvdimm-fixes (dax locking and __copy_user_nocache fixes).
>
> ---
>
> Dan Williams (33):
> device-dax: rename 'dax_dev' to 'dev_dax'
> dax: refactor dax-fs into a generic provider of 'struct dax_device' instances
> dax: add a facility to lookup a dax device by 'host' device name
> dax: introduce dax_operations
> pmem: add dax_operations support
> axon_ram: add dax_operations support
> brd: add dax_operations support
> dcssblk: add dax_operations support
> block: kill bdev_dax_capable()
> dax: introduce dax_direct_access()
> dm: add dax_device and dax_operations support
> dm: teach dm-targets to use a dax_device + dax_operations
> ext2, ext4, xfs: retrieve dax_device for iomap operations
> Revert "block: use DAX for partition table reads"
> filesystem-dax: convert to dax_direct_access()
> block, dax: convert bdev_dax_supported() to dax_direct_access()
> block: remove block_device_operations ->direct_access()
> x86, dax, pmem: remove indirection around memcpy_from_pmem()
> dax, pmem: introduce 'copy_from_iter' dax operation
> dm: add ->copy_from_iter() dax operation support
> filesystem-dax: convert to dax_copy_from_iter()
> dax, pmem: introduce an optional 'flush' dax_operation
> dm: add ->flush() dax operation support
> filesystem-dax: convert to dax_flush()
> x86, dax: replace clear_pmem() with open coded memset + dax_ops->flush
> x86, dax, libnvdimm: move wb_cache_pmem() to libnvdimm
> x86, libnvdimm, pmem: move arch_invalidate_pmem() to libnvdimm
> x86, libnvdimm, dax: stop abusing __copy_user_nocache
> uio, libnvdimm, pmem: implement cache bypass for all copy_from_iter() operations
> libnvdimm, pmem: fix persistence warning
> libnvdimm, nfit: enable support for volatile ranges
> filesystem-dax: gate calls to dax_flush() on QUEUE_FLAG_WC
> libnvdimm, pmem: disable dax flushing when pmem is fronting a volatile region
>
>
> MAINTAINERS | 2
> arch/powerpc/platforms/Kconfig | 1
> arch/powerpc/sysdev/axonram.c | 45 +++-
> arch/x86/Kconfig | 1
> arch/x86/include/asm/pmem.h | 141 ------------
> arch/x86/include/asm/string_64.h | 1
> block/Kconfig | 1
> block/partition-generic.c | 17 -
> drivers/Makefile | 2
> drivers/acpi/nfit/core.c | 15 +
> drivers/block/Kconfig | 1
> drivers/block/brd.c | 52 +++-
> drivers/dax/Kconfig | 10 +
> drivers/dax/Makefile | 5
> drivers/dax/dax.h | 15 -
> drivers/dax/device-dax.h | 25 ++
> drivers/dax/device.c | 415 +++++++++++------------------------
> drivers/dax/pmem.c | 10 -
> drivers/dax/super.c | 445 ++++++++++++++++++++++++++++++++++++++
> drivers/md/Kconfig | 1
> drivers/md/dm-core.h | 1
> drivers/md/dm-linear.c | 53 ++++-
> drivers/md/dm-snap.c | 6 -
> drivers/md/dm-stripe.c | 65 ++++--
> drivers/md/dm-target.c | 6 -
> drivers/md/dm.c | 112 ++++++++--
> drivers/nvdimm/Kconfig | 6 +
> drivers/nvdimm/Makefile | 1
> drivers/nvdimm/bus.c | 10 -
> drivers/nvdimm/claim.c | 9 -
> drivers/nvdimm/core.c | 2
> drivers/nvdimm/dax_devs.c | 2
> drivers/nvdimm/dimm_devs.c | 2
> drivers/nvdimm/namespace_devs.c | 9 -
> drivers/nvdimm/nd-core.h | 9 +
> drivers/nvdimm/pfn_devs.c | 4
> drivers/nvdimm/pmem.c | 82 +++++--
> drivers/nvdimm/pmem.h | 26 ++
> drivers/nvdimm/region_devs.c | 39 ++-
> drivers/nvdimm/x86.c | 155 +++++++++++++
> drivers/s390/block/Kconfig | 1
> drivers/s390/block/dcssblk.c | 44 +++-
> fs/block_dev.c | 117 +++-------
> fs/dax.c | 302 ++++++++++++++------------
> fs/ext2/inode.c | 9 +
> fs/ext4/inode.c | 9 +
> fs/iomap.c | 3
> fs/xfs/xfs_iomap.c | 10 +
> include/linux/blkdev.h | 19 --
> include/linux/dax.h | 43 +++-
> include/linux/device-mapper.h | 14 +
> include/linux/iomap.h | 1
> include/linux/libnvdimm.h | 10 +
> include/linux/pmem.h | 165 --------------
> include/linux/string.h | 8 +
> include/linux/uio.h | 4
> lib/Kconfig | 6 -
> lib/iov_iter.c | 25 ++
> tools/testing/nvdimm/Kbuild | 11 +
> tools/testing/nvdimm/pmem-dax.c | 21 +-
> 60 files changed, 1584 insertions(+), 1042 deletions(-)
> delete mode 100644 arch/x86/include/asm/pmem.h
> create mode 100644 drivers/dax/device-dax.h
> rename drivers/dax/{dax.c => device.c} (60%)
> create mode 100644 drivers/dax/super.c
> create mode 100644 drivers/nvdimm/x86.c
> delete mode 100644 include/linux/pmem.h
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