On 9/3/2024 5:34 PM, Jingbo Xu wrote:
>
> On 8/31/24 5:37 PM, Hou Tao wrote:
>> From: Hou Tao <houtao1@xxxxxxxxxx>
>>
>> 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.
> Actually, .wake_pending_and_unlock() is called under fiq->lock and
> GFP_ATOMIC is requisite.
Er, but virtio_fs_wake_pending_and_unlock() unlocks fiq->lock before
queuing the request.
>
>
>> Signed-off-by: Hou Tao <houtao1@xxxxxxxxxx>
>> ---
>> fs/fuse/virtio_fs.c | 24 +++++++++++++++---------
>> 1 file changed, 15 insertions(+), 9 deletions(-)
>>
>> diff --git a/fs/fuse/virtio_fs.c b/fs/fuse/virtio_fs.c
>> index 43d66ab5e891..9bc48b3ca384 100644
>> --- a/fs/fuse/virtio_fs.c
>> +++ b/fs/fuse/virtio_fs.c
>> @@ -95,7 +95,8 @@ 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 },
>> @@ -439,6 +440,8 @@ 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);
>> @@ -449,7 +452,9 @@ 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);
>> @@ -550,7 +555,7 @@ 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;
>> @@ -564,7 +569,7 @@ 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;
>>
>> @@ -1239,7 +1244,8 @@ 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];
>> @@ -1260,8 +1266,8 @@ 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;
>> @@ -1269,7 +1275,7 @@ 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;
>>
>> @@ -1367,7 +1373,7 @@ __releases(fiq->lock)
>> 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) {
>> /*
> LGTM.
>
> Reviewed-by: Jingbo Xu <jefflexu@xxxxxxxxxxxxxxxxx>
Thanks for the review.
>
>
