[PATCH 2/2] drm/i915: enable THP for gemfs

[Matthew Auld]

Signed-off-by: Matthew Auld <matthew.auld at intel.com>
---
 drivers/gpu/drm/i915/i915_gemfs.c | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_gemfs.c b/drivers/gpu/drm/i915/i915_gemfs.c
index 2620ffeaebe2..f1d6d5d14f91 100644
--- a/drivers/gpu/drm/i915/i915_gemfs.c
+++ b/drivers/gpu/drm/i915/i915_gemfs.c
@@ -29,6 +29,7 @@
 #include <linux/ramfs.h>
 #include <linux/pagemap.h>
 #include <linux/file.h>
+#include <linux/shmem_fs.h>
 
 #include "i915_drv.h"
 
@@ -36,10 +37,19 @@ static const struct dentry_operations anon_ops = {
 	.d_dname = simple_dname
 };
 
+static inline struct shmem_sb_info *SHMEM_SB(struct super_block *sb)
+{
+	return sb->s_fs_info;
+}
+
 int i915_gemfs_create(struct drm_i915_private *i915)
 {
 	struct file_system_type *type;
 	struct vfsmount *gemfs_mnt;
+	struct super_block *sb;
+	int flags = 0;
+	int ret;
+	char options[] = "huge=within_size";
 
 	type = get_fs_type("tmpfs");
 	if (!type) {
@@ -51,6 +61,25 @@ int i915_gemfs_create(struct drm_i915_private *i915)
 		return PTR_ERR(gemfs_mnt);
 	}
 
+	sb = gemfs_mnt->mnt_sb;
+
+#if defined(CONFIG_TRANSPARENT_HUGE_PAGECACHE)
+	/* 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 PTR_ERR(gemfs_mnt);
+	}
+
+	WARN_ON(SHMEM_SB(sb)->huge == 0);
+#endif
+
 	i915->gemfs_mnt = gemfs_mnt;
 
 	return 0;
-- 
2.9.4