Re: [PATCH] drm/amdgpu: Fix incorrect return value

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Am 03.04.24 um 09:06 schrieb YiPeng Chai:
   After calling amdgpu_vram_mgr_reserve_range
multiple times with the same address, calling
amdgpu_vram_mgr_query_page_status will always
return -EBUSY.
   From the second call to amdgpu_vram_mgr_reserve_range,
the same address will be added to the reservations_pending
list again and is never moved to the reserved_pages list
because the address had been reserved.

Well that sounds like a really bad idea to me. Why is the function called multiple times with the same address in the first place ?

Apart from that a note on the coding style below.

   First add the address status check before calling
amdgpu_vram_mgr_do_reserve, if the address is already
reserved, do nothing; If the address is already in the
reservations_pending list, directly reserve memory;
only add new nodes for the addresses that are not in the
reserved_pages list and reservations_pending list.

Signed-off-by: YiPeng Chai <YiPeng.Chai@xxxxxxx>
  drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c | 28 +++++++++++++-------
  1 file changed, 19 insertions(+), 9 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c
index 1e36c428d254..0bf3f4092900 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c
@@ -317,7 +317,6 @@ static void amdgpu_vram_mgr_do_reserve(struct ttm_resource_manager *man)
dev_dbg(adev->dev, "Reservation 0x%llx - %lld, Succeeded\n",
  			rsv->start, rsv->size);
  		vis_usage = amdgpu_vram_mgr_vis_size(adev, block);
  		atomic64_add(vis_usage, &mgr->vis_usage);
@@ -340,19 +339,30 @@ int amdgpu_vram_mgr_reserve_range(struct amdgpu_vram_mgr *mgr,
  				  uint64_t start, uint64_t size)
  	struct amdgpu_vram_reservation *rsv;
+	int ret = 0;

Don't initialize local variables when it isn't necessary.

- rsv = kzalloc(sizeof(*rsv), GFP_KERNEL);
-	if (!rsv)
-		return -ENOMEM;
+	ret = amdgpu_vram_mgr_query_page_status(mgr, start);
+	if (!ret)
+		return 0;
+	if (ret == -ENOENT) {
+		rsv = kzalloc(sizeof(*rsv), GFP_KERNEL);
+		if (!rsv)
+			return -ENOMEM;
- INIT_LIST_HEAD(&rsv->allocated);
-	INIT_LIST_HEAD(&rsv->blocks);
+		INIT_LIST_HEAD(&rsv->allocated);
+		INIT_LIST_HEAD(&rsv->blocks);
- rsv->start = start;
-	rsv->size = size;
+		rsv->start = start;
+		rsv->size = size;
+		mutex_lock(&mgr->lock);
+		list_add_tail(&rsv->blocks, &mgr->reservations_pending);
+		mutex_unlock(&mgr->lock);
+	}

You should probably not lock/unlock here.


-	list_add_tail(&rsv->blocks, &mgr->reservations_pending);

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