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-rw-r--r--arch/powerpc/platforms/Kconfig1
-rw-r--r--drivers/dax/super.c10
-rw-r--r--drivers/s390/block/Kconfig1
-rw-r--r--fs/Kconfig7
4 files changed, 19 insertions, 0 deletions
diff --git a/arch/powerpc/platforms/Kconfig b/arch/powerpc/platforms/Kconfig
index 5a96a2763e4a..2ce89b42a9f4 100644
--- a/arch/powerpc/platforms/Kconfig
+++ b/arch/powerpc/platforms/Kconfig
@@ -297,6 +297,7 @@ config AXON_RAM
tristate "Axon DDR2 memory device driver"
depends on PPC_IBM_CELL_BLADE && BLOCK
select DAX
+ select FS_DAX_LIMITED
default m
help
It registers one block device per Axon's DDR2 memory bank found
diff --git a/drivers/dax/super.c b/drivers/dax/super.c
index 3ec804672601..473af694ad1c 100644
--- a/drivers/dax/super.c
+++ b/drivers/dax/super.c
@@ -15,6 +15,7 @@
#include <linux/mount.h>
#include <linux/magic.h>
#include <linux/genhd.h>
+#include <linux/pfn_t.h>
#include <linux/cdev.h>
#include <linux/hash.h>
#include <linux/slab.h>
@@ -123,6 +124,15 @@ int __bdev_dax_supported(struct super_block *sb, int blocksize)
return len < 0 ? len : -EIO;
}
+ if ((IS_ENABLED(CONFIG_FS_DAX_LIMITED) && pfn_t_special(pfn))
+ || pfn_t_devmap(pfn))
+ /* pass */;
+ else {
+ pr_debug("VFS (%s): error: dax support not enabled\n",
+ sb->s_id);
+ return -EOPNOTSUPP;
+ }
+
return 0;
}
EXPORT_SYMBOL_GPL(__bdev_dax_supported);
diff --git a/drivers/s390/block/Kconfig b/drivers/s390/block/Kconfig
index bc27d716aa6b..1444333210c7 100644
--- a/drivers/s390/block/Kconfig
+++ b/drivers/s390/block/Kconfig
@@ -16,6 +16,7 @@ config BLK_DEV_XPRAM
config DCSSBLK
def_tristate m
select DAX
+ select FS_DAX_LIMITED
prompt "DCSSBLK support"
depends on S390 && BLOCK
help
diff --git a/fs/Kconfig b/fs/Kconfig
index 7aee6d699fd6..b40128bf6d1a 100644
--- a/fs/Kconfig
+++ b/fs/Kconfig
@@ -58,6 +58,13 @@ config FS_DAX_PMD
depends on ZONE_DEVICE
depends on TRANSPARENT_HUGEPAGE
+# Selected by DAX drivers that do not expect filesystem DAX to support
+# get_user_pages() of DAX mappings. I.e. "limited" indicates no support
+# for fork() of processes with MAP_SHARED mappings or support for
+# direct-I/O to a DAX mapping.
+config FS_DAX_LIMITED
+ bool
+
endif # BLOCK
# Posix ACL utility routines