fs/Kconfig:FS_DAX prevents DAX from building on architectures with
virtually aliased dcache with:
depends on !(ARM || MIPS || SPARC)
This check is too broad (e.g. recent ARMv7 don't have virtually aliased
dcaches), and also misses many other architectures with virtually
aliased dcache.
This is a regression introduced in the v5.13 Linux kernel where the
dax mount option is removed for 32-bit ARMv7 boards which have no dcache
aliasing, and therefore should work fine with FS_DAX.
Use this instead in Kconfig to prevent FS_DAX from being built on
architectures with virtually aliased dcache:
depends on !ARCH_HAS_CACHE_ALIASING
For architectures which detect dcache aliasing at runtime, introduce
a new dax_is_supported() static inline which uses "cache_is_aliasing()"
to figure out whether the environment has aliasing dcaches.
This new dax_is_supported() helper will be used in each filesystem
supporting the dax mount option to validate whether dax is indeed
supported.
Fixes: d92576f1167c ("dax: does not work correctly with virtual aliasing caches")
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: linux-mm@xxxxxxxxx
Cc: linux-arch@xxxxxxxxxxxxxxx
Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
Cc: Vishal Verma <vishal.l.verma@xxxxxxxxx>
Cc: Dave Jiang <dave.jiang@xxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: nvdimm@xxxxxxxxxxxxxxx
Cc: linux-cxl@xxxxxxxxxxxxxxx
---
fs/Kconfig | 2 +-
include/linux/dax.h | 9 +++++++++
2 files changed, 10 insertions(+), 1 deletion(-)
diff --git a/fs/Kconfig b/fs/Kconfig
index 42837617a55b..6746fe403761 100644
--- a/fs/Kconfig
+++ b/fs/Kconfig
@@ -56,7 +56,7 @@ endif # BLOCK
config FS_DAX
bool "File system based Direct Access (DAX) support"
depends on MMU
- depends on !(ARM || MIPS || SPARC)
+ depends on !ARCH_HAS_CACHE_ALIASING
depends on ZONE_DEVICE || FS_DAX_LIMITED
select FS_IOMAP
select DAX
diff --git a/include/linux/dax.h b/include/linux/dax.h
index b463502b16e1..8c595b04deeb 100644
--- a/include/linux/dax.h
+++ b/include/linux/dax.h
@@ -5,6 +5,7 @@
#include <linux/fs.h>
#include <linux/mm.h>
#include <linux/radix-tree.h>
+#include <linux/cacheinfo.h>
typedef unsigned long dax_entry_t;
@@ -78,6 +79,10 @@ static inline bool daxdev_mapping_supported(struct vm_area_struct *vma,
return false;
return dax_synchronous(dax_dev);
}
+static inline bool dax_is_supported(void)
+{
+ return !cache_is_aliasing();
+}
#else
static inline void *dax_holder(struct dax_device *dax_dev)
{
@@ -122,6 +127,10 @@ static inline size_t dax_recovery_write(struct dax_device *dax_dev,
{
return 0;
}
+static inline bool dax_is_supported(void)
+{
+ return false;
+}
#endif
void set_dax_nocache(struct dax_device *dax_dev);
--
2.39.2
