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-rw-r--r--fs/Kconfig6
-rw-r--r--fs/dax.c4
2 files changed, 10 insertions, 0 deletions
diff --git a/fs/Kconfig b/fs/Kconfig
index da3f32f1a4e4..6ce72d8d1ee1 100644
--- a/fs/Kconfig
+++ b/fs/Kconfig
@@ -46,6 +46,12 @@ config FS_DAX
or if unsure, say N. Saying Y will increase the size of the kernel
by about 5kB.
+config FS_DAX_PMD
+ bool
+ default FS_DAX
+ depends on FS_DAX
+ depends on BROKEN
+
endif # BLOCK
# Posix ACL utility routines
diff --git a/fs/dax.c b/fs/dax.c
index d1e5cb7311a1..43671b68220e 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -541,6 +541,10 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
unsigned long pfn;
int result = 0;
+ /* dax pmd mappings are broken wrt gup and fork */
+ if (!IS_ENABLED(CONFIG_FS_DAX_PMD))
+ return VM_FAULT_FALLBACK;
+
/* Fall back to PTEs if we're going to COW */
if (write && !(vma->vm_flags & VM_SHARED))
return VM_FAULT_FALLBACK;