[PATCH 02/15] 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 | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_gemfs.c b/drivers/gpu/drm/i915/i915_gemfs.c
index e1b2af1d9946..7b50ff97623e 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>
 
 static const struct dentry_operations anon_ops = {
 	.d_dname = simple_dname
@@ -41,6 +42,28 @@ struct vfsmount *i915_gemfs_create(void)
 
 	gemfs_mnt = kern_mount(type);
 
+#if defined(CONFIG_TRANSPARENT_HUGE_PAGECACHE)
+	if (!IS_ERR(gemfs_mnt) && has_transparent_hugepage()) {
+		struct super_block *sb = gemfs_mnt->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_mnt);
+			return ERR_PTR(ret);
+		}
+	}
+#endif
+
 	return gemfs_mnt;
 }
 
-- 
2.9.4