io_uring: abstract out provided buffer list selection

In preparation for providing another way to select a buffer, move the
existing logic into a helper.

Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 26b69ff..3d5a4e6 100644 (file)
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -3448,29 +3448,41 @@ static int io_buffer_add_list(struct io_ring_ctx *ctx,
        return xa_err(xa_store(&ctx->io_bl_xa, bgid, bl, GFP_KERNEL));
 }
 
+static void __user *io_provided_buffer_select(struct io_kiocb *req, size_t *len,
+                                             struct io_buffer_list *bl,
+                                             unsigned int issue_flags)
+{
+       struct io_buffer *kbuf;
+
+       if (list_empty(&bl->buf_list))
+               return ERR_PTR(-ENOBUFS);
+
+       kbuf = list_first_entry(&bl->buf_list, struct io_buffer, list);
+       list_del(&kbuf->list);
+       if (*len > kbuf->len)
+               *len = kbuf->len;
+       req->flags |= REQ_F_BUFFER_SELECTED;
+       req->kbuf = kbuf;
+       io_ring_submit_unlock(req->ctx, issue_flags);
+       return u64_to_user_ptr(kbuf->addr);
+}
+
 static void __user *io_buffer_select(struct io_kiocb *req, size_t *len,
                                     unsigned int issue_flags)
 {
-       struct io_buffer *kbuf = req->kbuf;
        struct io_ring_ctx *ctx = req->ctx;
        struct io_buffer_list *bl;
 
        io_ring_submit_lock(req->ctx, issue_flags);
 
        bl = io_buffer_get_list(ctx, req->buf_index);
-       if (bl && !list_empty(&bl->buf_list)) {
-               kbuf = list_first_entry(&bl->buf_list, struct io_buffer, list);
-               list_del(&kbuf->list);
-               if (*len > kbuf->len)
-                       *len = kbuf->len;
-               req->flags |= REQ_F_BUFFER_SELECTED;
-               req->kbuf = kbuf;
+       if (unlikely(!bl)) {
                io_ring_submit_unlock(req->ctx, issue_flags);
-               return u64_to_user_ptr(kbuf->addr);
+               return ERR_PTR(-ENOBUFS);
        }
 
-       io_ring_submit_unlock(req->ctx, issue_flags);
-       return ERR_PTR(-ENOBUFS);
+       /* selection helpers drop the submit lock again, if needed */
+       return io_provided_buffer_select(req, len, bl, issue_flags);
 }
 
 #ifdef CONFIG_COMPAT