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Subject[PATCH 3/3] pmem: Allow request_mem to fail, (CONFIG_BLK_DEV_PMEM_IGNORE_REQUEST_MEM_RET)

With old Kernels there was a bug in x86 where any unknown
memory chip type would come up BUSY when calling

So for pmem to work with old Kernels and real NvDIMM chips
we have a new Kconfig option CONFIG_BLK_DEV_PMEM_IGNORE_REQUEST_MEM_RET.

People have been running with hacked up pmem that will ignore
the return code from request_mem_region_exclusive. So here it is

Signed-off-by: Boaz Harrosh <>
drivers/block/Kconfig | 12 ++++++++++++
drivers/block/pmem.c | 11 +++++++----
2 files changed, 19 insertions(+), 4 deletions(-)

diff --git a/drivers/block/Kconfig b/drivers/block/Kconfig
index 3b3200f..10879b8 100644
--- a/drivers/block/Kconfig
+++ b/drivers/block/Kconfig
@@ -430,6 +430,18 @@ config BLK_DEV_PMEM_USE_PAGES
to other devices in the system, then you must say "Yes" here.
If unsure leave as Yes.

+ bool "Ignore the return code from request_mem_region_exclusive"
+ depends on BLK_DEV_PMEM
+ help
+ In Old Kernels type-12 Memory type which is used by NvDIMM
+ chips Comes out busy when calling request_mem_region_exclusive,
+ because of a bug.
+ If this option is set to "yes". The pmem will ignore the
+ failure, and continue as usual. If you have an old Kernel and
+ a real NvDIMM chip you must say yes here.
+ (Ignored if BLK_DEV_PMEM_USE_PAGES=y)
tristate "Packet writing on CD/DVD media"
depends on !UML
diff --git a/drivers/block/pmem.c b/drivers/block/pmem.c
index 9eb7ffe..f84d033 100644
--- a/drivers/block/pmem.c
+++ b/drivers/block/pmem.c
@@ -197,10 +197,12 @@ int pmem_mapmem(struct pmem_device *pmem)

res_mem = request_mem_region_exclusive(pmem->phys_addr, pmem->size,
- if (!res_mem) {
+ if (unlikely(!res_mem)) {
pr_warn("pmem: request_mem_region_exclusive phys=0x%llx size=0x%zx failed\n",
- pmem->phys_addr, pmem->size);
- return -EINVAL;
+ pmem->phys_addr, pmem->size);
+ return -EBUSY;

pmem->virt_addr = ioremap_cache(pmem->phys_addr, pmem->size);
@@ -211,7 +213,8 @@ int pmem_mapmem(struct pmem_device *pmem)
return 0;

- release_mem_region(pmem->phys_addr, pmem->size);
+ if (res_mem)
+ release_mem_region(pmem->phys_addr, pmem->size);
return err;


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