[RFC v4 5/8] dmabuf: Add gpu cgroup charge transfer function
T.J. Mercier
tjmercier at google.com
Mon Mar 28 03:59:44 UTC 2022
From: Hridya Valsaraju <hridya at google.com>
The dma_buf_charge_transfer function provides a way for processes to
transfer charge of a buffer to a different process. This is essential
for the cases where a central allocator process does allocations for
various subsystems, hands over the fd to the client who requested the
memory and drops all references to the allocated memory.
Signed-off-by: Hridya Valsaraju <hridya at google.com>
Signed-off-by: T.J. Mercier <tjmercier at google.com>
---
v4 changes
Adjust ordering of charge/uncharge during transfer to avoid potentially
hitting cgroup limit per Michal Koutný.
v3 changes
Use more common dual author commit message format per John Stultz.
v2 changes
Move dma-buf cgroup charge transfer from a dma_buf_op defined by every
heap to a single dma-buf function for all heaps per Daniel Vetter and
Christian König.
---
drivers/dma-buf/dma-buf.c | 49 +++++++++++++++++++++++++++++++
include/linux/cgroup_gpu.h | 12 ++++++++
include/linux/dma-buf.h | 2 ++
kernel/cgroup/gpu.c | 59 ++++++++++++++++++++++++++++++++++++++
4 files changed, 122 insertions(+)
diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
index 1ee5c60d3d6d..7748c3453b91 100644
--- a/drivers/dma-buf/dma-buf.c
+++ b/drivers/dma-buf/dma-buf.c
@@ -1380,6 +1380,55 @@ void dma_buf_vunmap(struct dma_buf *dmabuf, struct dma_buf_map *map)
}
EXPORT_SYMBOL_NS_GPL(dma_buf_vunmap, DMA_BUF);
+/**
+ * dma_buf_transfer_charge - Change the GPU cgroup to which the provided dma_buf is charged.
+ * @dmabuf: [in] buffer whose charge will be migrated to a different GPU cgroup
+ * @gpucg: [in] the destination GPU cgroup for dmabuf's charge
+ *
+ * Only tasks that belong to the same cgroup the buffer is currently charged to
+ * may call this function, otherwise it will return -EPERM.
+ *
+ * Returns 0 on success, or a negative errno code otherwise.
+ */
+int dma_buf_transfer_charge(struct dma_buf *dmabuf, struct gpucg *gpucg)
+{
+#ifdef CONFIG_CGROUP_GPU
+ struct gpucg *current_gpucg;
+ int ret;
+
+ /* If the source and destination cgroups are the same, don't do anything. */
+ current_gpucg = gpucg_get(current);
+ if (current_gpucg == gpucg) {
+ ret = 0;
+ goto skip_transfer;
+ }
+
+ /*
+ * Verify that the cgroup of the process requesting the transfer is the
+ * same as the one the buffer is currently charged to.
+ */
+ current_gpucg = gpucg_get(current);
+ mutex_lock(&dmabuf->lock);
+ if (current_gpucg != dmabuf->gpucg) {
+ ret = -EPERM;
+ goto err;
+ }
+
+ ret = gpucg_transfer_charge(current_gpucg, gpucg, dmabuf->gpucg_dev, dmabuf->size);
+ if (ret)
+ goto err;
+ dmabuf->gpucg = gpucg;
+err:
+ mutex_unlock(&dmabuf->lock);
+skip_transfer:
+ gpucg_put(current_gpucg);
+ return ret;
+#else
+ return 0;
+#endif /* CONFIG_CGROUP_GPU */
+}
+EXPORT_SYMBOL_NS_GPL(dma_buf_transfer_charge, DMA_BUF);
+
#ifdef CONFIG_DEBUG_FS
static int dma_buf_debug_show(struct seq_file *s, void *unused)
{
diff --git a/include/linux/cgroup_gpu.h b/include/linux/cgroup_gpu.h
index c90069719022..e30f15d5e9be 100644
--- a/include/linux/cgroup_gpu.h
+++ b/include/linux/cgroup_gpu.h
@@ -87,6 +87,10 @@ static inline struct gpucg *gpucg_parent(struct gpucg *cg)
int gpucg_try_charge(struct gpucg *gpucg, struct gpucg_device *device, u64 usage);
void gpucg_uncharge(struct gpucg *gpucg, struct gpucg_device *device, u64 usage);
+int gpucg_transfer_charge(struct gpucg *source,
+ struct gpucg *dest,
+ struct gpucg_device *device,
+ u64 usage);
void gpucg_register_device(struct gpucg_device *gpucg_dev, const char *name);
#else /* CONFIG_CGROUP_GPU */
@@ -121,6 +125,14 @@ static inline void gpucg_uncharge(struct gpucg *gpucg,
struct gpucg_device *device,
u64 usage) {}
+static inline int gpucg_transfer_charge(struct gpucg *source,
+ struct gpucg *dest,
+ struct gpucg_device *device,
+ u64 usage)
+{
+ return 0;
+}
+
static inline void gpucg_register_device(struct gpucg_device *gpucg_dev,
const char *name) {}
#endif /* CONFIG_CGROUP_GPU */
diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h
index 742f29c3daaf..646827156213 100644
--- a/include/linux/dma-buf.h
+++ b/include/linux/dma-buf.h
@@ -646,4 +646,6 @@ int dma_buf_mmap(struct dma_buf *, struct vm_area_struct *,
unsigned long);
int dma_buf_vmap(struct dma_buf *dmabuf, struct dma_buf_map *map);
void dma_buf_vunmap(struct dma_buf *dmabuf, struct dma_buf_map *map);
+
+int dma_buf_transfer_charge(struct dma_buf *dmabuf, struct gpucg *gpucg);
#endif /* __DMA_BUF_H__ */
diff --git a/kernel/cgroup/gpu.c b/kernel/cgroup/gpu.c
index ac4c470914b5..40531323d6da 100644
--- a/kernel/cgroup/gpu.c
+++ b/kernel/cgroup/gpu.c
@@ -247,6 +247,65 @@ void gpucg_uncharge(struct gpucg *gpucg, struct gpucg_device *device, u64 usage)
css_put_many(&gpucg->css, nr_pages);
}
+/**
+ * gpucg_transfer_charge - Transfer a GPU charge from one cgroup to another.
+ * @source: [in] The GPU cgroup the charge will be transferred from.
+ * @dest: [in] The GPU cgroup the charge will be transferred to.
+ * @device: [in] The GPU cgroup device corresponding to the charge.
+ * @usage: [in] The size of the memory in bytes.
+ *
+ * Returns 0 on success, or a negative errno code otherwise.
+ */
+int gpucg_transfer_charge(struct gpucg *source,
+ struct gpucg *dest,
+ struct gpucg_device *device,
+ u64 usage)
+{
+ struct page_counter *counter;
+ u64 nr_pages;
+ struct gpucg_resource_pool *rp_source, *rp_dest;
+ int ret = 0;
+
+ nr_pages = PAGE_ALIGN(usage) >> PAGE_SHIFT;
+
+ mutex_lock(&gpucg_mutex);
+ rp_source = find_cg_rpool_locked(source, device);
+ if (unlikely(!rp_source)) {
+ ret = -ENOENT;
+ goto exit_early;
+ }
+
+ rp_dest = get_cg_rpool_locked(dest, device);
+ if (IS_ERR(rp_dest)) {
+ ret = PTR_ERR(rp_dest);
+ goto exit_early;
+ }
+
+ /*
+ * First uncharge from the pool it's currently charged to. This ordering avoids double
+ * charging while the transfer is in progress, which could cause us to hit a limit.
+ * If the try_charge fails for this transfer, we need to be able to reverse this uncharge,
+ * so we continue to hold the gpucg_mutex here.
+ */
+ page_counter_uncharge(&rp_source->total, nr_pages);
+ css_put_many(&source->css, nr_pages);
+
+ /* Now attempt the new charge */
+ if (page_counter_try_charge(&rp_dest->total, nr_pages, &counter)) {
+ css_get_many(&dest->css, nr_pages);
+ } else {
+ /*
+ * The new charge failed, so reverse the uncharge from above. This should always
+ * succeed since charges on source are blocked by gpucg_mutex.
+ */
+ WARN_ON(!page_counter_try_charge(&rp_source->total, nr_pages, &counter));
+ css_get_many(&source->css, nr_pages);
+ }
+exit_early:
+ mutex_unlock(&gpucg_mutex);
+ return ret;
+}
+
/**
* gpucg_register_device - Registers a device for memory accounting using the
* GPU cgroup controller.
--
2.35.1.1021.g381101b075-goog
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