drm/xe: Add a shrinker for xe bos

Rather than relying on the TTM watermark accounting add a shrinker
for xe_bos in TT or system memory.

Leverage the newly added TTM per-page shrinking and shmem backup
support.

Although xe doesn't fully support WONTNEED (purgeable) bos yet,
introduce and add shrinker support for purgeable ttm_tts.

v2:
- Cleanups bugfixes and a KUNIT shrinker test.
- Add writeback support, and activate if kswapd.
v3:
- Move the try_shrink() helper to core TTM.
- Minor cleanups.
v4:
- Add runtime pm for the shrinker. Shrinking may require an active
  device for CCS metadata copying.
v5:
- Separately purge ghost- and zombie objects in the shrinker.
- Fix a format specifier - type inconsistency. (Kernel test robot).
v7:
- s/long/s64/ (Christian König)
- s/sofar/progress/ (Matt Brost)
v8:
- Rebase on Xe KUNIT update.
- Add content verifying to the shrinker kunit test.
- Split out TTM changes to a separate patch.
- Get rid of multiple bool arguments for clarity (Matt Brost)
- Avoid an error pointer dereference (Matt Brost)
- Avoid an integer overflow (Matt Auld)
- Address misc review comments by Matt Brost.
v9:
- Fix a compliation error.
- Rebase.
v10:
- Update to new LRU walk interface.
- Rework ghost-, zombie and purged object shrinking.
- Rebase.
v11:
- Use additional TTM helpers.
- Honor __GFP_FS and __GFP_IO
- Rebase.
v13:
- Use ttm_tt_setup_backup().
v14:
- Don't set up backup on imported bos.
v15:
- Rebase on backup interface changes.

Cc: Christian König <christian.koenig@amd.com>
Cc: Somalapuram Amaranath <Amaranath.Somalapuram@amd.com>
Cc: Matthew Brost <matthew.brost@intel.com>
Cc: <dri-devel@lists.freedesktop.org>
Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Acked-by: Christian König <christian.koenig@amd.com>
Link: https://lore.kernel.org/intel-xe/20250305092220.123405-7-thomas.hellstrom@linux.intel.com

drivers/gpu/drm/xe/tests/xe_bo.c

@@ -514,8 +514,13 @@ static int shrink_test_run_device(struct xe_device *xe)
 		 * other way around, they may not be subject to swapping...
 		 */
 		if (alloced < purgeable) {
+			xe_ttm_tt_account_subtract(&xe_tt->ttm);
 			xe_tt->purgeable = true;
+			xe_ttm_tt_account_add(&xe_tt->ttm);
 			bo->ttm.priority = 0;
+			spin_lock(&bo->ttm.bdev->lru_lock);
+			ttm_bo_move_to_lru_tail(&bo->ttm);
+			spin_unlock(&bo->ttm.bdev->lru_lock);
 		} else {
 			int ret = shrink_test_fill_random(bo, &prng, link);
 
@@ -570,7 +575,6 @@ static int shrink_test_run_device(struct xe_device *xe)
 				if (ret == -EINTR)
 					intr = true;
 			} while (ret == -EINTR && !signal_pending(current));
-
 			if (!ret && !purgeable)
 				failed = shrink_test_verify(test, bo, count, &prng, link);