On 3/9/24 05:26, Hou Tao wrote:
> Hi,
>
> On 3/1/2024 9:42 PM, Miklos Szeredi wrote:
>> On Wed, 28 Feb 2024 at 15:40, Hou Tao <hou...@huaweicloud.com> wrote:
>>
>>> So instead of limiting both the values of max_read and max_write in
>>> kernel, capping the maximal length of kvec iter IO by using max_pages in
>>> fuse_direct_io() just like it does for ubuf/iovec iter IO. Now the max
>>> value for max_pages is 256, so on host with 4KB page size, the maximal
>>> size passed to kmalloc() in copy_args_to_argbuf() is about 1MB+40B. The
>>> allocation of 2MB of physically contiguous memory will still incur
>>> significant stress on the memory subsystem, but the warning is fixed.
>>> Additionally, the requirement for huge physically contiguous memory will
>>> be removed in the following patch.
>> So the issue will be fixed properly by following patches?
>>
>> In that case this patch could be omitted, right?
>
> Sorry for the late reply. Being busy with off-site workshop these days.
>
> No, this patch is still necessary and it is used to limit the number of
> scatterlist used for fuse request and reply in virtio-fs. If the length
> of out_args[0].size is not limited, the number of scatterlist used to
> map the fuse request may be greater than the queue size of virtio-queue
> and the fuse request may hang forever.
I'm currently also totally busy and didn't carefully check, but isn't
there something missing that limits fc->max_write/fc->max_read?
Thanks,
Bernd
