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authorDan Williams <dan.j.williams@intel.com>2017-07-10 15:48:25 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2017-07-10 16:32:31 -0700
commitbaabda261424517110ea98c6651f632ebf2561e3 (patch)
treecf02e6ec756e3c090ac7bfe463dc237b7b9e10ab /include
parent16981d763501c0e06e434cf6b59f964c520e0ccc (diff)
mm: always enable thp for dax mappings
The madvise policy for transparent huge pages is meant to avoid unwanted allocations of transparent huge pages. It allows a policy of disabling the extra memory pressure and effort to arrange for a huge page when it is not needed. DAX by definition never incurs this overhead since it is statically allocated. The policy choice makes even less sense for device-dax which tries to guarantee a given tlb-fault size. Specifically, the following setting: echo never > /sys/kernel/mm/transparent_hugepage/enabled ...violates that guarantee and silently disables all device-dax instances with a 2M or 1G alignment. So, let's avoid that non-obvious side effect by force enabling thp for dax mappings in all cases. It is worth noting that the reason this uses vma_is_dax(), and the resulting header include changes, is that previous attempts to add a VM_DAX flag were NAKd. Link: http://lkml.kernel.org/r/149739531127.20686.15813586620597484283.stgit@dwillia2-desk3.amr.corp.intel.com Signed-off-by: Dan Williams <dan.j.williams@intel.com> Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com> Cc: Jan Kara <jack@suse.cz> Cc: Christoph Hellwig <hch@lst.de> Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> Cc: Michal Hocko <mhocko@suse.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include')
-rw-r--r--include/linux/dax.h5
-rw-r--r--include/linux/fs.h6
-rw-r--r--include/linux/huge_mm.h5
3 files changed, 11 insertions, 5 deletions
diff --git a/include/linux/dax.h b/include/linux/dax.h
index 8f39db7439c3..794811875732 100644
--- a/include/linux/dax.h
+++ b/include/linux/dax.h
@@ -154,11 +154,6 @@ static inline unsigned int dax_radix_order(void *entry)
#endif
int dax_pfn_mkwrite(struct vm_fault *vmf);
-static inline bool vma_is_dax(struct vm_area_struct *vma)
-{
- return vma->vm_file && IS_DAX(vma->vm_file->f_mapping->host);
-}
-
static inline bool dax_mapping(struct address_space *mapping)
{
return mapping->host && IS_DAX(mapping->host);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 0cfa47125d52..78e1dbbe4cfd 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -18,6 +18,7 @@
#include <linux/bug.h>
#include <linux/mutex.h>
#include <linux/rwsem.h>
+#include <linux/mm_types.h>
#include <linux/capability.h>
#include <linux/semaphore.h>
#include <linux/fcntl.h>
@@ -3127,6 +3128,11 @@ static inline bool io_is_direct(struct file *filp)
return (filp->f_flags & O_DIRECT) || IS_DAX(filp->f_mapping->host);
}
+static inline bool vma_is_dax(struct vm_area_struct *vma)
+{
+ return vma->vm_file && IS_DAX(vma->vm_file->f_mapping->host);
+}
+
static inline int iocb_flags(struct file *file)
{
int res = 0;
diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
index f4239d3c9c73..ee696347f928 100644
--- a/include/linux/huge_mm.h
+++ b/include/linux/huge_mm.h
@@ -3,6 +3,8 @@
#include <linux/sched/coredump.h>
+#include <linux/fs.h> /* only for vma_is_dax() */
+
extern int do_huge_pmd_anonymous_page(struct vm_fault *vmf);
extern int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr,
@@ -103,6 +105,9 @@ static inline bool transparent_hugepage_enabled(struct vm_area_struct *vma)
if (transparent_hugepage_flags & (1 << TRANSPARENT_HUGEPAGE_FLAG))
return true;
+ if (vma_is_dax(vma))
+ return true;
+
if (transparent_hugepage_flags &
(1 << TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG))
return !!(vma->vm_flags & VM_HUGEPAGE);