drm/pagemap: Add a drm_pagemap cache and shrinker

Pagemaps are costly to set up and tear down, and they consume a lot
of system memory for the struct pages. Ideally they should be
created only when needed.

Add a caching mechanism to allow doing just that: Create the drm_pagemaps
when needed for migration. Keep them around to avoid destruction and
re-creation latencies and destroy inactive/unused drm_pagemaps on memory
pressure using a shrinker.

Only add the helper functions. They will be hooked up to the xe driver
in the upcoming patch.

v2:
- Add lockdep checking for drm_pagemap_put(). (Matt Brost)
- Add a copyright notice. (Matt Brost)

Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Acked-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com> # For merging through drm-xe.
Link: https://patch.msgid.link/20251219113320.183860-8-thomas.hellstrom@linux.intel.com

1 files changed, 2 insertions, 1 deletions

diff --git a/drivers/gpu/drm/Makefile b/drivers/gpu/drm/Makefile
index 0e1c668b46d2..0deee72ef935 100644
--- a/drivers/gpu/drm/Makefile
+++ b/drivers/gpu/drm/Makefile
@@ -109,7 +109,8 @@ obj-$(CONFIG_DRM_GPUVM) += drm_gpuvm.o
 
 drm_gpusvm_helper-y := \
 	drm_gpusvm.o\
-	drm_pagemap.o
+	drm_pagemap.o\
+	drm_pagemap_util.o
 obj-$(CONFIG_DRM_GPUSVM) += drm_gpusvm_helper.o
 
 obj-$(CONFIG_DRM_BUDDY) += drm_buddy.o