[PATCH v5 1/2] drm/xe/shrinker: Do not discard freed pages on error

[Shuicheng Lin <shuicheng.lin@intel.com>]

__xe_shrinker_walk() and xe_shrinker_walk() both return the error in
place of the pages they have already freed.  xe_shrinker_scan() only
accumulates non-negative returns, so those pages are never reported,
while *scanned is updated by pointer and does count them.  The shrinker
then tells mm that it scanned without freeing, which skews the reclaim
accounting away from it.

Report what was freed when there is something to report, and the error
only when there is not.

v2: drop EBUSY check and add more return check. (Sashiko)

Reported-by: Sashiko <sashiko-bot@kernel.org>
Fixes: 00c8efc3180f ("drm/xe: Add a shrinker for xe bos")
Assisted-by: Claude:claude-opus-5
Cc: stable@vger.kernel.org
Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Cc: Matthew Brost <matthew.brost@intel.com>
Signed-off-by: Shuicheng Lin <shuicheng.lin@intel.com>
---
 drivers/gpu/drm/xe/xe_shrinker.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/xe/xe_shrinker.c b/drivers/gpu/drm/xe/xe_shrinker.c
index 83374cd57660..7f40153911ff 100644
--- a/drivers/gpu/drm/xe/xe_shrinker.c
+++ b/drivers/gpu/drm/xe/xe_shrinker.c
@@ -80,7 +80,7 @@ static s64 __xe_shrinker_walk(struct xe_device *xe,
 
 			lret = xe_bo_shrink(ctx, ttm_bo, flags, scanned);
 			if (lret < 0)
-				return lret;
+				return freed ? freed : lret;
 
 			freed += lret;
 			if (*scanned >= to_scan)
@@ -119,7 +119,7 @@ static s64 xe_shrinker_walk(struct xe_device *xe,
 	if (!ctx->no_wait_gpu) {
 		lret = __xe_shrinker_walk(xe, ctx, save_flags, to_scan, scanned);
 		if (lret < 0)
-			return lret;
+			return freed ? freed : lret;
 		freed += lret;
 		if (*scanned >= to_scan)
 			return freed;
@@ -128,7 +128,7 @@ static s64 xe_shrinker_walk(struct xe_device *xe,
 	if (flags.writeback) {
 		lret = __xe_shrinker_walk(xe, ctx, flags, to_scan, scanned);
 		if (lret < 0)
-			return lret;
+			return freed ? freed : lret;
 		freed += lret;
 	}
 
-- 
2.43.0