[PATCH 02/17] drm/i915: enable THP for gemfs

[Matthew Auld]

Enable transparent-huge-pages through gemfs by mounting with
huge=within_size.

Signed-off-by: Matthew Auld <matthew.auld at intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
Cc: Chris Wilson <chris at chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/i915_gemfs.c | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_gemfs.c b/drivers/gpu/drm/i915/i915_gemfs.c
index 5464f6ceaccb..c4b7050c30d3 100644
--- a/drivers/gpu/drm/i915/i915_gemfs.c
+++ b/drivers/gpu/drm/i915/i915_gemfs.c
@@ -25,6 +25,7 @@
 #include <linux/fs.h>
 #include <linux/file.h>
 #include <linux/mount.h>
+#include <linux/pagemap.h>
 
 #include "i915_drv.h"
 #include "i915_gemfs.h"
@@ -46,6 +47,27 @@ int i915_gemfs_init(struct drm_i915_private *i915)
 	if (IS_ERR(gemfs))
 		return PTR_ERR(gemfs);
 
+#if defined(CONFIG_TRANSPARENT_HUGE_PAGECACHE)
+	if (has_transparent_hugepage()) {
+		struct super_block *sb = gemfs->mnt_sb;
+		char options[] = "huge=within_size";
+		int flags = 0;
+		int ret;
+
+		/* Idealy we would just pass the mount options when mounting,
+		 * but for some reason shmem chooses not to parse the options
+		 * for MS_KERNMOUNT, probably because shm_mnt is the only tmpfs
+		 * kernel mount other than this, where the mount options aren't
+		 * used. To workaround this we do a remount, which is fairly
+		 * inexpensive, where we know the options are never igonored.
+		 */
+		ret = sb->s_op->remount_fs(sb, &flags, options);
+		if (ret) {
+			kern_unmount(gemfs);
+			return ret;
+		}
+	}
+#endif
 	i915->gemfs = gemfs;
 
 	return 0;
-- 
2.9.4