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authorDan Williams <dan.j.williams@intel.com>2016-05-14 22:20:44 +0300
committerDan Williams <dan.j.williams@intel.com>2016-05-21 08:02:55 +0300
commitdee410792419aaa8bc3e3b35d2ccb6515835916d (patch)
treeb63a073ff7e6bad601ac7c45d3b0a156d906b052 /drivers/dax/Kconfig
parentab68f26221366f92611650e8470e6a926801c7d4 (diff)
downloadlinux-dee410792419aaa8bc3e3b35d2ccb6515835916d.tar.xz
/dev/dax, core: file operations and dax-mmap
The "Device DAX" core enables dax mappings of performance / feature differentiated memory. An open mapping or file handle keeps the backing struct device live, but new mappings are only possible while the device is enabled. Faults are handled under rcu_read_lock to synchronize with the enabled state of the device. Similar to the filesystem-dax case the backing memory may optionally have struct page entries. However, unlike fs-dax there is no support for private mappings, or mappings that are not backed by media (see use of zero-page in fs-dax). Mappings are always guaranteed to match the alignment of the dax_region. If the dax_region is configured to have a 2MB alignment, all mappings are guaranteed to be backed by a pmd entry. Contrast this determinism with the fs-dax case where pmd mappings are opportunistic. If userspace attempts to force a misaligned mapping, the driver will fail the mmap attempt. See dax_dev_check_vma() for other scenarios that are rejected, like MAP_PRIVATE mappings. Cc: Hannes Reinecke <hare@suse.de> Cc: Jeff Moyer <jmoyer@redhat.com> Cc: Christoph Hellwig <hch@lst.de> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: Ross Zwisler <ross.zwisler@linux.intel.com> Acked-by: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Diffstat (limited to 'drivers/dax/Kconfig')
-rw-r--r--drivers/dax/Kconfig1
1 files changed, 1 insertions, 0 deletions
diff --git a/drivers/dax/Kconfig b/drivers/dax/Kconfig
index 86ffbaa891ad..cedab7572de3 100644
--- a/drivers/dax/Kconfig
+++ b/drivers/dax/Kconfig
@@ -1,6 +1,7 @@
menuconfig DEV_DAX
tristate "DAX: direct access to differentiated memory"
default m if NVDIMM_DAX
+ depends on TRANSPARENT_HUGEPAGE
help
Support raw access to differentiated (persistence, bandwidth,
latency...) memory via an mmap(2) capable character