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author | 2017-05-29 12:22:50 -0700 | |
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committer | 2017-06-09 09:09:56 -0700 | |
commit | 0aed55af88345b5d673240f90e671d79662fb01e (patch) | |
tree | b4ebcb7d95e47a7fef48558daafc0e527c1e60ca /drivers/nvdimm/pmem.c | |
parent | Linux 4.12-rc4 (diff) | |
download | linux-0aed55af88345b5d673240f90e671d79662fb01e.tar.gz linux-0aed55af88345b5d673240f90e671d79662fb01e.tar.bz2 linux-0aed55af88345b5d673240f90e671d79662fb01e.zip |
x86, uaccess: introduce copy_from_iter_flushcache for pmem / cache-bypass operations
The pmem driver has a need to transfer data with a persistent memory
destination and be able to rely on the fact that the destination writes are not
cached. It is sufficient for the writes to be flushed to a cpu-store-buffer
(non-temporal / "movnt" in x86 terms), as we expect userspace to call fsync()
to ensure data-writes have reached a power-fail-safe zone in the platform. The
fsync() triggers a REQ_FUA or REQ_FLUSH to the pmem driver which will turn
around and fence previous writes with an "sfence".
Implement a __copy_from_user_inatomic_flushcache, memcpy_page_flushcache, and
memcpy_flushcache, that guarantee that the destination buffer is not dirty in
the cpu cache on completion. The new copy_from_iter_flushcache and sub-routines
will be used to replace the "pmem api" (include/linux/pmem.h +
arch/x86/include/asm/pmem.h). The availability of copy_from_iter_flushcache()
and memcpy_flushcache() are gated by the CONFIG_ARCH_HAS_UACCESS_FLUSHCACHE
config symbol, and fallback to copy_from_iter_nocache() and plain memcpy()
otherwise.
This is meant to satisfy the concern from Linus that if a driver wants to do
something beyond the normal nocache semantics it should be something private to
that driver [1], and Al's concern that anything uaccess related belongs with
the rest of the uaccess code [2].
The first consumer of this interface is a new 'copy_from_iter' dax operation so
that pmem can inject cache maintenance operations without imposing this
overhead on other dax-capable drivers.
[1]: https://lists.01.org/pipermail/linux-nvdimm/2017-January/008364.html
[2]: https://lists.01.org/pipermail/linux-nvdimm/2017-April/009942.html
Cc: <x86@kernel.org>
Cc: Jan Kara <jack@suse.cz>
Cc: Jeff Moyer <jmoyer@redhat.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Toshi Kani <toshi.kani@hpe.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Matthew Wilcox <mawilcox@microsoft.com>
Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Diffstat (limited to 'drivers/nvdimm/pmem.c')
-rw-r--r-- | drivers/nvdimm/pmem.c | 13 |
1 files changed, 11 insertions, 2 deletions
diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c index c544d466ea51..2f3aefe565c6 100644 --- a/drivers/nvdimm/pmem.c +++ b/drivers/nvdimm/pmem.c @@ -29,6 +29,7 @@ #include <linux/pfn_t.h> #include <linux/slab.h> #include <linux/pmem.h> +#include <linux/uio.h> #include <linux/dax.h> #include <linux/nd.h> #include "pmem.h" @@ -80,7 +81,7 @@ static void write_pmem(void *pmem_addr, struct page *page, { void *mem = kmap_atomic(page); - memcpy_to_pmem(pmem_addr, mem + off, len); + memcpy_flushcache(pmem_addr, mem + off, len); kunmap_atomic(mem); } @@ -235,8 +236,15 @@ static long pmem_dax_direct_access(struct dax_device *dax_dev, return __pmem_direct_access(pmem, pgoff, nr_pages, kaddr, pfn); } +static size_t pmem_copy_from_iter(struct dax_device *dax_dev, pgoff_t pgoff, + void *addr, size_t bytes, struct iov_iter *i) +{ + return copy_from_iter_flushcache(addr, bytes, i); +} + static const struct dax_operations pmem_dax_ops = { .direct_access = pmem_dax_direct_access, + .copy_from_iter = pmem_copy_from_iter, }; static void pmem_release_queue(void *q) @@ -294,7 +302,8 @@ static int pmem_attach_disk(struct device *dev, dev_set_drvdata(dev, pmem); pmem->phys_addr = res->start; pmem->size = resource_size(res); - if (nvdimm_has_flush(nd_region) < 0) + if (!IS_ENABLED(CONFIG_ARCH_HAS_UACCESS_FLUSHCACHE) + || nvdimm_has_flush(nd_region) < 0) dev_warn(dev, "unable to guarantee persistence of writes\n"); if (!devm_request_mem_region(dev, res->start, resource_size(res), |