libnvdimm/pfn: Fix namespace creation on misaligned addresses

Yi reported[1] that after commit a3619190d62e ("libnvdimm/pfn: stop
padding pmem namespaces to section alignment"), it was no longer
possible to create a device dax namespace with a 1G alignment.  The
reason was that the pmem region was not itself 1G-aligned.  The code
happily skips past the first 512M, but fails to account for a now
misaligned end offset (since space was allocated starting at that
misaligned address, and extending for size GBs).  Reintroduce
end_trunc, so that the code correctly handles the misaligned end
address.  This results in the same behavior as before the introduction
of the offending commit.

[1] https://lists.01.org/pipermail/linux-nvdimm/2019-July/022813.html

Fixes: a3619190d62e ("libnvdimm/pfn: stop padding pmem namespaces ...")
Reported-and-tested-by: Yi Zhang <yi.zhang@redhat.com>
Signed-off-by: Jeff Moyer <jmoyer@redhat.com>
Link: https://lore.kernel.org/r/x49ftll8f39.fsf@segfault.boston.devel.redhat.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

diff --git a/drivers/nvdimm/pfn_devs.c b/drivers/nvdimm/pfn_devs.c
index 3e7b11c..cb98b8f 100644 (file)
--- a/drivers/nvdimm/pfn_devs.c
+++ b/drivers/nvdimm/pfn_devs.c
@@ -655,6 +655,7 @@ static int nd_pfn_init(struct nd_pfn *nd_pfn)
        resource_size_t start, size;
        struct nd_region *nd_region;
        unsigned long npfns, align;
+       u32 end_trunc;
        struct nd_pfn_sb *pfn_sb;
        phys_addr_t offset;
        const char *sig;
@@ -696,6 +697,7 @@ static int nd_pfn_init(struct nd_pfn *nd_pfn)
        size = resource_size(&nsio->res);
        npfns = PHYS_PFN(size - SZ_8K);
        align = max(nd_pfn->align, (1UL << SUBSECTION_SHIFT));
+       end_trunc = start + size - ALIGN_DOWN(start + size, align);
        if (nd_pfn->mode == PFN_MODE_PMEM) {
                /*
                 * The altmap should be padded out to the block size used
@@ -714,7 +716,7 @@ static int nd_pfn_init(struct nd_pfn *nd_pfn)
                return -ENXIO;
        }
 
-       npfns = PHYS_PFN(size - offset);
+       npfns = PHYS_PFN(size - offset - end_trunc);
        pfn_sb->mode = cpu_to_le32(nd_pfn->mode);
        pfn_sb->dataoff = cpu_to_le64(offset);
        pfn_sb->npfns = cpu_to_le64(npfns);
@@ -723,6 +725,7 @@ static int nd_pfn_init(struct nd_pfn *nd_pfn)
        memcpy(pfn_sb->parent_uuid, nd_dev_to_uuid(&ndns->dev), 16);
        pfn_sb->version_major = cpu_to_le16(1);
        pfn_sb->version_minor = cpu_to_le16(3);
+       pfn_sb->end_trunc = cpu_to_le32(end_trunc);
        pfn_sb->align = cpu_to_le32(nd_pfn->align);
        checksum = nd_sb_checksum((struct nd_gen_sb *) pfn_sb);
        pfn_sb->checksum = cpu_to_le64(checksum);