Hi, On 3/1/2024 9:42 PM, Miklos Szeredi wrote: > On Wed, 28 Feb 2024 at 15:40, Hou Tao <houtao@xxxxxxxxxxxxxxx> 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. > > Thanks, > Miklos
