+ dax-fix-incorrect-list-of-data-cache-aliasing-architectures.patch added to mm-unstable branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: dax: fix incorrect list of data cache aliasing architectures
has been added to the -mm mm-unstable branch.  Its filename is
     dax-fix-incorrect-list-of-data-cache-aliasing-architectures.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/dax-fix-incorrect-list-of-data-cache-aliasing-architectures.patch

This patch will later appear in the mm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Subject: dax: fix incorrect list of data cache aliasing architectures
Date: Thu, 8 Feb 2024 13:49:09 -0500

commit d92576f1167c ("dax: does not work correctly with virtual aliasing
caches") 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
data cache.

This is a regression introduced in the v4.0 Linux kernel where the dax
mount option is removed for 32-bit ARMv7 boards which have no data cache
aliasing, and therefore should work fine with FS_DAX.

This was turned into the following check in alloc_dax() by a preparatory
change:

        if (ops && (IS_ENABLED(CONFIG_ARM) ||
            IS_ENABLED(CONFIG_MIPS) ||
            IS_ENABLED(CONFIG_SPARC)))
                return NULL;

Use cpu_dcache_is_aliasing() instead to figure out whether the environment
has aliasing data caches.

Link: https://lkml.kernel.org/r/20240208184913.484340-9-mathieu.desnoyers@efficios.com
Fixes: d92576f1167c ("dax: does not work correctly with virtual aliasing caches")
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Vishal Verma <vishal.l.verma@intel.com>
Cc: Dave Jiang <dave.jiang@intel.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Alasdair Kergon <agk@redhat.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Mike Snitzer <snitzer@kernel.org>
Cc: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 drivers/dax/super.c |    5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

--- a/drivers/dax/super.c~dax-fix-incorrect-list-of-data-cache-aliasing-architectures
+++ a/drivers/dax/super.c
@@ -13,6 +13,7 @@
 #include <linux/uio.h>
 #include <linux/dax.h>
 #include <linux/fs.h>
+#include <linux/cacheinfo.h>
 #include "dax-private.h"
 
 /**
@@ -456,9 +457,7 @@ struct dax_device *alloc_dax(void *priva
 	 * except for device-dax (NULL operations pointer), which does
 	 * not use aliased mappings from the kernel.
 	 */
-	if (ops && (IS_ENABLED(CONFIG_ARM) ||
-	    IS_ENABLED(CONFIG_MIPS) ||
-	    IS_ENABLED(CONFIG_SPARC)))
+	if (ops && cpu_dcache_is_aliasing())
 		return ERR_PTR(-EOPNOTSUPP);
 
 	if (WARN_ON_ONCE(ops && !ops->zero_page_range))
_

Patches currently in -mm which might be from mathieu.desnoyers@efficios.com are

nvdimm-pmem-fix-leak-on-dax_add_host-failure.patch
nvdimm-pmem-treat-alloc_dax-eopnotsupp-failure-as-non-fatal.patch
dm-treat-alloc_dax-eopnotsupp-failure-as-non-fatal.patch
dcssblk-handle-alloc_dax-eopnotsupp-failure.patch
virtio-treat-alloc_dax-eopnotsupp-failure-as-non-fatal.patch
dax-check-for-data-cache-aliasing-at-runtime.patch
introduce-cpu_dcache_is_aliasing-across-all-architectures.patch
dax-fix-incorrect-list-of-data-cache-aliasing-architectures.patch
nvdimm-pmem-cleanup-alloc_dax-error-handling.patch
dm-cleanup-alloc_dax-error-handling.patch
dcssblk-cleanup-alloc_dax-error-handling.patch
virtio-cleanup-alloc_dax-error-handling.patch