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    Subject[PATCH 4.9 78/80] libnvdimm, pfn: fix npfns vs section alignment
    Date
    4.9-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Dan Williams <dan.j.williams@intel.com>

    commit d5483feda85a8f39ee2e940e279547c686aac30c upstream.

    Fix failures to create namespaces due to the vmem_altmap not advertising
    enough free space to store the memmap.

    WARNING: CPU: 15 PID: 8022 at arch/x86/mm/init_64.c:656 arch_add_memory+0xde/0xf0
    [..]
    Call Trace:
    dump_stack+0x63/0x83
    __warn+0xcb/0xf0
    warn_slowpath_null+0x1d/0x20
    arch_add_memory+0xde/0xf0
    devm_memremap_pages+0x244/0x440
    pmem_attach_disk+0x37e/0x490 [nd_pmem]
    nd_pmem_probe+0x7e/0xa0 [nd_pmem]
    nvdimm_bus_probe+0x71/0x120 [libnvdimm]
    driver_probe_device+0x2bb/0x460
    bind_store+0x114/0x160
    drv_attr_store+0x25/0x30

    In commit 658922e57b84 "libnvdimm, pfn: fix memmap reservation sizing"
    we arranged for the capacity to be allocated, but failed to also update
    the 'npfns' parameter. This leads to cases where there is enough
    capacity reserved to hold all the allocated sections, but
    vmemmap_populate_hugepages() still encounters -ENOMEM from
    altmap_alloc_block_buf().

    This fix is a stop-gap until we can teach the core memory hotplug
    implementation to permit sub-section hotplug.

    Fixes: 658922e57b84 ("libnvdimm, pfn: fix memmap reservation sizing")
    Reported-by: Anisha Allada <anisha.allada@intel.com>
    Signed-off-by: Dan Williams <dan.j.williams@intel.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    drivers/nvdimm/pfn_devs.c | 6 ++++--
    1 file changed, 4 insertions(+), 2 deletions(-)

    --- a/drivers/nvdimm/pfn_devs.c
    +++ b/drivers/nvdimm/pfn_devs.c
    @@ -538,7 +538,8 @@ static struct vmem_altmap *__nvdimm_setu
    nd_pfn->npfns = le64_to_cpu(pfn_sb->npfns);
    altmap = NULL;
    } else if (nd_pfn->mode == PFN_MODE_PMEM) {
    - nd_pfn->npfns = (resource_size(res) - offset) / PAGE_SIZE;
    + nd_pfn->npfns = PFN_SECTION_ALIGN_UP((resource_size(res)
    + - offset) / PAGE_SIZE);
    if (le64_to_cpu(nd_pfn->pfn_sb->npfns) > nd_pfn->npfns)
    dev_info(&nd_pfn->dev,
    "number of pfns truncated from %lld to %ld\n",
    @@ -625,7 +626,8 @@ static int nd_pfn_init(struct nd_pfn *nd
    */
    start += start_pad;
    size = resource_size(&nsio->res);
    - npfns = (size - start_pad - end_trunc - SZ_8K) / SZ_4K;
    + npfns = PFN_SECTION_ALIGN_UP((size - start_pad - end_trunc - SZ_8K)
    + / PAGE_SIZE);
    if (nd_pfn->mode == PFN_MODE_PMEM) {
    /*
    * vmemmap_populate_hugepages() allocates the memmap array in

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