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| author | Dan Williams <dan.j.williams@intel.com> | 2020-01-30 12:06:23 -0800 |
|---|---|---|
| committer | Dan Williams <dan.j.williams@intel.com> | 2020-03-17 12:23:21 -0700 |
| commit | 2522afb86a8cceba0f67dbf05772d21b76d79f06 (patch) | |
| tree | 43ea32614b10933889836813b187d1e52eaf766d /drivers/nvdimm/nd.h | |
| parent | a0e374525def2ef18a078523e1faefb5ce2b05e5 (diff) | |
| download | lwn-2522afb86a8cceba0f67dbf05772d21b76d79f06.tar.gz lwn-2522afb86a8cceba0f67dbf05772d21b76d79f06.zip | |
libnvdimm/region: Introduce an 'align' attribute
The align attribute applies an alignment constraint for namespace
creation in a region. Whereas the 'align' attribute of a namespace
applied alignment padding via an info block, the 'align' attribute
applies alignment constraints to the free space allocation.
The default for 'align' is the maximum known memremap_compat_align()
across all archs (16MiB from PowerPC at time of writing) multiplied by
the number of interleave ways if there is blk-aliasing. The minimum is
PAGE_SIZE and allows for the creation of cross-arch incompatible
namespaces, just as previous kernels allowed, but the expectation is
cross-arch and mode-independent compatibility by default.
The regression risk with this change is limited to cases that were
dependent on the ability to create unaligned namespaces, *and* for some
reason are unable to opt-out of aligned namespaces by writing to
'regionX/align'. If such a scenario arises the default can be flipped
from opt-out to opt-in of compat-aligned namespace creation, but that is
a last resort. The kernel will otherwise continue to support existing
defined misaligned namespaces.
Unfortunately this change needs to touch several parts of the
implementation at once:
- region/available_size: expand busy extents to current align
- region/max_available_extent: expand busy extents to current align
- namespace/size: trim free space to current align
...to keep the free space accounting conforming to the dynamic align
setting.
Reported-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Reported-by: Jeff Moyer <jmoyer@redhat.com>
Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Reviewed-by: Jeff Moyer <jmoyer@redhat.com>
Link: https://lore.kernel.org/r/158041478371.3889308.14542630147672668068.stgit@dwillia2-desk3.amr.corp.intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Diffstat (limited to 'drivers/nvdimm/nd.h')
| -rw-r--r-- | drivers/nvdimm/nd.h | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/drivers/nvdimm/nd.h b/drivers/nvdimm/nd.h index ca39abe29c7c..c4d69c1cce55 100644 --- a/drivers/nvdimm/nd.h +++ b/drivers/nvdimm/nd.h @@ -146,6 +146,7 @@ struct nd_region { struct device *btt_seed; struct device *pfn_seed; struct device *dax_seed; + unsigned long align; u16 ndr_mappings; u64 ndr_size; u64 ndr_start; |