Commit 86b74eb5 authored by Hou Tao's avatar Hou Tao Committed by Miklos Szeredi
Browse files

virtiofs: use GFP_NOFS when enqueuing request through kworker 



When invoking virtio_fs_enqueue_req() through kworker, both the
allocation of the sg array and the bounce buffer still use GFP_ATOMIC.
Considering the size of the sg array may be greater than PAGE_SIZE, use
GFP_NOFS instead of GFP_ATOMIC to lower the possibility of memory
allocation failure and to avoid unnecessarily depleting the atomic
reserves. GFP_NOFS is not passed to virtio_fs_enqueue_req() directly,
GFP_KERNEL and memalloc_nofs_{save|restore} helpers are used instead.

It may seem OK to pass GFP_NOFS to virtio_fs_enqueue_req() as well when
queuing the request for the first time, but this is not the case. The
reason is that fuse_request_queue_background() may call
->queue_request_and_unlock() while holding fc->bg_lock, which is a
spin-lock. Therefore, still use GFP_ATOMIC for it.

Signed-off-by: default avatarHou Tao <houtao1@huawei.com>
Reviewed-by: default avatarJingbo Xu <jefflexu@linux.alibaba.com>
Signed-off-by: default avatarMiklos Szeredi <mszeredi@redhat.com>
parent 41748675

fs/fuse/virtio_fs.c

+15 −9
Original line number Diff line number Diff line
@@ -97,7 +97,8 @@ struct virtio_fs_req_work { 
};



static int virtio_fs_enqueue_req(struct virtio_fs_vq *fsvq,

				 struct fuse_req *req, bool in_flight);

				 struct fuse_req *req, bool in_flight,

				 gfp_t gfp);



static const struct constant_table dax_param_enums[] = {

	{"always",	FUSE_DAX_ALWAYS },
@@ -575,6 +576,8 @@ static void virtio_fs_request_dispatch_work(struct work_struct *work) 


	/* Dispatch pending requests */

	while (1) {

		unsigned int flags;



		spin_lock(&fsvq->lock);

		req = list_first_entry_or_null(&fsvq->queued_reqs,

					       struct fuse_req, list);
@@ -585,7 +588,9 @@ static void virtio_fs_request_dispatch_work(struct work_struct *work) 
		list_del_init(&req->list);

		spin_unlock(&fsvq->lock);



		ret = virtio_fs_enqueue_req(fsvq, req, true);

		flags = memalloc_nofs_save();

		ret = virtio_fs_enqueue_req(fsvq, req, true, GFP_KERNEL);

		memalloc_nofs_restore(flags);

		if (ret < 0) {

			if (ret == -ENOSPC) {

				spin_lock(&fsvq->lock);
@@ -686,7 +691,7 @@ static void virtio_fs_hiprio_dispatch_work(struct work_struct *work) 
}



/* Allocate and copy args into req->argbuf */

static int copy_args_to_argbuf(struct fuse_req *req)

static int copy_args_to_argbuf(struct fuse_req *req, gfp_t gfp)

{

	struct fuse_args *args = req->args;

	unsigned int offset = 0;
@@ -700,7 +705,7 @@ static int copy_args_to_argbuf(struct fuse_req *req) 
	len = fuse_len_args(num_in, (struct fuse_arg *) args->in_args) +

	      fuse_len_args(num_out, args->out_args);



	req->argbuf = kmalloc(len, GFP_ATOMIC);

	req->argbuf = kmalloc(len, gfp);

	if (!req->argbuf)

		return -ENOMEM;
@@ -1366,7 +1371,8 @@ static unsigned int sg_init_fuse_args(struct scatterlist *sg, 


/* Add a request to a virtqueue and kick the device */

static int virtio_fs_enqueue_req(struct virtio_fs_vq *fsvq,

				 struct fuse_req *req, bool in_flight)

				 struct fuse_req *req, bool in_flight,

				 gfp_t gfp)

{

	/* requests need at least 4 elements */

	struct scatterlist *stack_sgs[6];
@@ -1387,8 +1393,8 @@ static int virtio_fs_enqueue_req(struct virtio_fs_vq *fsvq, 
	/* Does the sglist fit on the stack? */

	total_sgs = sg_count_fuse_req(req);

	if (total_sgs > ARRAY_SIZE(stack_sgs)) {

		sgs = kmalloc_array(total_sgs, sizeof(sgs[0]), GFP_ATOMIC);

		sg = kmalloc_array(total_sgs, sizeof(sg[0]), GFP_ATOMIC);

		sgs = kmalloc_array(total_sgs, sizeof(sgs[0]), gfp);

		sg = kmalloc_array(total_sgs, sizeof(sg[0]), gfp);

		if (!sgs || !sg) {

			ret = -ENOMEM;

			goto out;
@@ -1396,7 +1402,7 @@ static int virtio_fs_enqueue_req(struct virtio_fs_vq *fsvq, 
	}



	/* Use a bounce buffer since stack args cannot be mapped */

	ret = copy_args_to_argbuf(req);

	ret = copy_args_to_argbuf(req, gfp);

	if (ret < 0)

		goto out;
@@ -1490,7 +1496,7 @@ static void virtio_fs_send_req(struct fuse_iqueue *fiq, struct fuse_req *req) 
		 queue_id);



	fsvq = &fs->vqs[queue_id];

	ret = virtio_fs_enqueue_req(fsvq, req, false);

	ret = virtio_fs_enqueue_req(fsvq, req, false, GFP_ATOMIC);

	if (ret < 0) {

		if (ret == -ENOSPC) {

			/*