Merge branch 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6

[karo-tx-linux.git] / drivers / nvdimm / pmem.c

diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
index 8e09c544d892eadfff181bc67c6f9f135adefcaa..f798899338eddb6955c06f5b44c26c405dffdade 100644 (file)
--- a/drivers/nvdimm/pmem.c
+++ b/drivers/nvdimm/pmem.c
@@ -103,6 +103,20 @@ static int pmem_do_bvec(struct pmem_device *pmem, struct page *page,
                        flush_dcache_page(page);
                }
        } else {
+               /*
+                * Note that we write the data both before and after
+                * clearing poison.  The write before clear poison
+                * handles situations where the latest written data is
+                * preserved and the clear poison operation simply marks
+                * the address range as valid without changing the data.
+                * In this case application software can assume that an
+                * interrupted write will either return the new good
+                * data or an error.
+                *
+                * However, if pmem_clear_poison() leaves the data in an
+                * indeterminate state we need to perform the write
+                * after clear poison.
+                */
                flush_dcache_page(page);
                memcpy_to_pmem(pmem_addr, mem + off, len);
                if (unlikely(bad_pmem)) {