On 26.09.2019 18:52, Andrey Ryabinin wrote:
> From: Miklos Szeredi <[email protected]>
>
> Allow the kernel read and write on "direct_io" files. This is
> necessary for nfs export and execute support.
>
> The implementation is simple: if an access from the kernel is
> detected, don't perform get_user_pages(), just use the kernel address
> provided by the requester to copy from/to the userspace filesystem.
>
> Signed-off-by: Miklos Szeredi <[email protected]>
>
> https://jira.sw.ru/browse/PSBM-97905
> (cherry picked from commit f4975c67dd9ad8eb47a4c77af0521a2b16ee0197)
> Signed-off-by: Andrey Ryabinin <[email protected]>
> ---
> fs/fuse/file.c | 12 ++++++++++++
> 1 file changed, 12 insertions(+)
>
> diff --git a/fs/fuse/file.c b/fs/fuse/file.c
> index 344f35562bbe..ec8a0b07a5d6 100644
> --- a/fs/fuse/file.c
> +++ b/fs/fuse/file.c
> @@ -1702,6 +1702,18 @@ static int fuse_get_user_pages(struct fuse_req *req,
> struct iov_iter *ii,
> size_t *nbytesp, int write)
> {
> size_t nbytes = 0; /* # bytes already packed in req */
> + /* Special case for kernel I/O: can copy directly into the buffer */
> + if (segment_eq(get_fs(), KERNEL_DS)) {
> + unsigned long user_addr = fuse_get_user_addr(ii);
> + size_t frag_size = fuse_get_frag_size(ii, *nbytesp);
'frag_size' is not used here. Should it be removed?
> +
> + if (write)
> + req->in.args[1].value = (void *) user_addr;
> + else
> + req->out.args[0].value = (void *) user_addr;
> +
> + return 0;
> + }
>
> while (nbytes < *nbytesp && req->num_pages < req->max_pages) {
> unsigned npages;
>
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