On 4/26/2024 10:39 PM, Hou Tao wrote:
> From: Hou Tao <houtao1@xxxxxxxxxx>
>
> When trying to insert a 10MB kernel module kept in a virtio-fs with cache
> disabled, the following warning was reported:
>
> ------------[ cut here ]------------
> WARNING: CPU: 1 PID: 404 at mm/page_alloc.c:4551 ......
> Modules linked in:
> CPU: 1 PID: 404 Comm: insmod Not tainted 6.9.0-rc5+ #123
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996) ......
> RIP: 0010:__alloc_pages+0x2bf/0x380
> ......
> Call Trace:
> <TASK>
> ? __warn+0x8e/0x150
> ? __alloc_pages+0x2bf/0x380
> __kmalloc_large_node+0x86/0x160
> __kmalloc+0x33c/0x480
> virtio_fs_enqueue_req+0x240/0x6d0
> virtio_fs_wake_pending_and_unlock+0x7f/0x190
> queue_request_and_unlock+0x55/0x60
> fuse_simple_request+0x152/0x2b0
> fuse_direct_io+0x5d2/0x8c0
> fuse_file_read_iter+0x121/0x160
> __kernel_read+0x151/0x2d0
> kernel_read+0x45/0x50
> kernel_read_file+0x1a9/0x2a0
> init_module_from_file+0x6a/0xe0
> idempotent_init_module+0x175/0x230
> __x64_sys_finit_module+0x5d/0xb0
> x64_sys_call+0x1c3/0x9e0
> do_syscall_64+0x3d/0xc0
> entry_SYSCALL_64_after_hwframe+0x4b/0x53
> ......
> </TASK>
> ---[ end trace 0000000000000000 ]---
>
> The warning is triggered as follows:
>
SNIP
> @@ -1585,7 +1589,7 @@ ssize_t fuse_direct_io(struct fuse_io_priv *io, struct iov_iter *iter,
> size_t nbytes = min(count, nmax);
>
> err = fuse_get_user_pages(&ia->ap, iter, &nbytes, write,
> - max_pages);
> + max_pages, fc->use_pages_for_kvec_io);
> if (err && !nbytes)
> break;
Just find out that flush_kernel_vmap_range() and
invalidate_kernel_vmap_range() should be used before DMA rw operation
and after DMA read operation if the kvec IO is backed by vmalloc() area.
Will update it in v4.
>
> diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
> index f239196103137..d4f04e19058c1 100644
> --- a/fs/fuse/fuse_i.h
> +++ b/fs/fuse/fuse_i.h
> @@ -860,6 +860,9 @@ struct fuse_conn {
> /** Passthrough support for read/write IO */
> unsigned int passthrough:1;
>
> + /* Use pages instead of pointer for kernel I/O */
> + unsigned int use_pages_for_kvec_io:1;
> +
> /** Maximum stack depth for passthrough backing files */
> int max_stack_depth;
>
> diff --git a/fs/fuse/virtio_fs.c b/fs/fuse/virtio_fs.c
> index 322af827a2329..36984c0e23d14 100644
> --- a/fs/fuse/virtio_fs.c
> +++ b/fs/fuse/virtio_fs.c
> @@ -1512,6 +1512,7 @@ static int virtio_fs_get_tree(struct fs_context *fsc)
> fc->delete_stale = true;
> fc->auto_submounts = true;
> fc->sync_fs = true;
> + fc->use_pages_for_kvec_io = true;
>
> /* Tell FUSE to split requests that exceed the virtqueue's size */
> fc->max_pages_limit = min_t(unsigned int, fc->max_pages_limit,
