mm, vmalloc: use __GFP_HIGHMEM implicitly

__vmalloc* allows users to provide gfp flags for the underlying
allocation.  This API is quite popular

  $ git grep "=[[:space:]]__vmalloc\|return[[:space:]]*__vmalloc" | wc -l
  77

The only problem is that many people are not aware that they really want
to give __GFP_HIGHMEM along with other flags because there is really no
reason to consume precious lowmemory on CONFIG_HIGHMEM systems for pages
which are mapped to the kernel vmalloc space.  About half of users don't
use this flag, though.  This signals that we make the API unnecessarily
too complex.

This patch simply uses __GFP_HIGHMEM implicitly when allocating pages to
be mapped to the vmalloc space.  Current users which add __GFP_HIGHMEM
are simplified and drop the flag.

Link: http://lkml.kernel.org/r/20170307141020.29107-1-mhocko@kernel.org
Signed-off-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Matthew Wilcox <mawilcox@microsoft.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: David Rientjes <rientjes@google.com>
Cc: Cristopher Lameter <cl@linux.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

4 files changed, 10 insertions, 11 deletions

diff --git a/mm/kasan/kasan.c b/mm/kasan/kasan.c
index 9348d27088c1..b10da59cf765 100644
--- a/mm/kasan/kasan.c
+++ b/mm/kasan/kasan.c
@@ -691,7 +691,7 @@ int kasan_module_alloc(void *addr, size_t size)
 
 	ret = __vmalloc_node_range(shadow_size, 1, shadow_start,
 			shadow_start + shadow_size,
-			GFP_KERNEL | __GFP_HIGHMEM | __GFP_ZERO,
+			GFP_KERNEL | __GFP_ZERO,
 			PAGE_KERNEL, VM_NO_GUARD, NUMA_NO_NODE,
 			__builtin_return_address(0));
 
diff --git a/mm/nommu.c b/mm/nommu.c
index a80411d258fc..fc184f597d59 100644
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -246,8 +246,7 @@ void *vmalloc_user(unsigned long size)
 {
 	void *ret;
 
-	ret = __vmalloc(size, GFP_KERNEL | __GFP_HIGHMEM | __GFP_ZERO,
-			PAGE_KERNEL);
+	ret = __vmalloc(size, GFP_KERNEL | __GFP_ZERO, PAGE_KERNEL);
 	if (ret) {
 		struct vm_area_struct *vma;
 
diff --git a/mm/util.c b/mm/util.c
index f4e590b2c0da..718154debc87 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -382,7 +382,7 @@ void *kvmalloc_node(size_t size, gfp_t flags, int node)
 	if (ret || size <= PAGE_SIZE)
 		return ret;
 
-	return __vmalloc_node_flags(size, node, flags | __GFP_HIGHMEM);
+	return __vmalloc_node_flags(size, node, flags);
 }
 EXPORT_SYMBOL(kvmalloc_node);
 
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 717b1e8b942c..1dda6d8a200a 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -1655,7 +1655,7 @@ static void *__vmalloc_area_node(struct vm_struct *area, gfp_t gfp_mask,
 	struct page **pages;
 	unsigned int nr_pages, array_size, i;
 	const gfp_t nested_gfp = (gfp_mask & GFP_RECLAIM_MASK) | __GFP_ZERO;
-	const gfp_t alloc_mask = gfp_mask | __GFP_NOWARN;
+	const gfp_t alloc_mask = gfp_mask | __GFP_HIGHMEM | __GFP_NOWARN;
 
 	nr_pages = get_vm_area_size(area) >> PAGE_SHIFT;
 	array_size = (nr_pages * sizeof(struct page *));
@@ -1818,7 +1818,7 @@ EXPORT_SYMBOL(__vmalloc);
 void *vmalloc(unsigned long size)
 {
 	return __vmalloc_node_flags(size, NUMA_NO_NODE,
-				    GFP_KERNEL | __GFP_HIGHMEM);
+				    GFP_KERNEL);
 }
 EXPORT_SYMBOL(vmalloc);
 
@@ -1835,7 +1835,7 @@ EXPORT_SYMBOL(vmalloc);
 void *vzalloc(unsigned long size)
 {
 	return __vmalloc_node_flags(size, NUMA_NO_NODE,
-				GFP_KERNEL | __GFP_HIGHMEM | __GFP_ZERO);
+				GFP_KERNEL | __GFP_ZERO);
 }
 EXPORT_SYMBOL(vzalloc);
 
@@ -1852,7 +1852,7 @@ void *vmalloc_user(unsigned long size)
 	void *ret;
 
 	ret = __vmalloc_node(size, SHMLBA,
-			     GFP_KERNEL | __GFP_HIGHMEM | __GFP_ZERO,
+			     GFP_KERNEL | __GFP_ZERO,
 			     PAGE_KERNEL, NUMA_NO_NODE,
 			     __builtin_return_address(0));
 	if (ret) {
@@ -1876,7 +1876,7 @@ EXPORT_SYMBOL(vmalloc_user);
  */
 void *vmalloc_node(unsigned long size, int node)
 {
-	return __vmalloc_node(size, 1, GFP_KERNEL | __GFP_HIGHMEM, PAGE_KERNEL,
+	return __vmalloc_node(size, 1, GFP_KERNEL, PAGE_KERNEL,
 					node, __builtin_return_address(0));
 }
 EXPORT_SYMBOL(vmalloc_node);
@@ -1896,7 +1896,7 @@ EXPORT_SYMBOL(vmalloc_node);
 void *vzalloc_node(unsigned long size, int node)
 {
 	return __vmalloc_node_flags(size, node,
-			 GFP_KERNEL | __GFP_HIGHMEM | __GFP_ZERO);
+			 GFP_KERNEL | __GFP_ZERO);
 }
 EXPORT_SYMBOL(vzalloc_node);
 
@@ -1918,7 +1918,7 @@ EXPORT_SYMBOL(vzalloc_node);
 
 void *vmalloc_exec(unsigned long size)
 {
-	return __vmalloc_node(size, 1, GFP_KERNEL | __GFP_HIGHMEM, PAGE_KERNEL_EXEC,
+	return __vmalloc_node(size, 1, GFP_KERNEL, PAGE_KERNEL_EXEC,
 			      NUMA_NO_NODE, __builtin_return_address(0));
 }