io_uring: don't pass around fixed index for scm

There is an old API nuisance where io_uring's SCM accounting functions
traverse fixed file tables and so requires them to be set in advance,
which leads to some implicit rules of how io_sqe_file_register() should
be used.

__io_sqe_files_scm() now works with only one file at a time, pass a file
directly and get rid of all fixed table dereferencing inside. Clean
io_sqe_file_register() callers.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/fb32031d892e61a7748c70da7999725d5e798671.1649334991.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/fs/io_uring.c b/fs/io_uring.c
index cbc8ddb..f97a0a5 100644 (file)
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -8609,9 +8609,8 @@ static struct io_sq_data *io_get_sq_data(struct io_uring_params *p,
  * files because otherwise they can't form a loop and so are not interesting
  * for GC.
  */
-static int __io_sqe_files_scm(struct io_ring_ctx *ctx, int offset)
+static int __io_sqe_files_scm(struct io_ring_ctx *ctx, struct file *file)
 {
-       struct file *file = io_file_from_index(ctx, offset);
        struct sock *sk = ctx->ring_sock->sk;
        struct scm_fp_list *fpl;
        struct sk_buff *skb;
@@ -8761,8 +8760,7 @@ static void io_rsrc_put_work(struct work_struct *work)
        }
 }
 
-static int io_sqe_file_register(struct io_ring_ctx *ctx, struct file *file,
-                               int index);
+static int io_sqe_file_register(struct io_ring_ctx *ctx, struct file *file);
 
 static int io_sqe_files_register(struct io_ring_ctx *ctx, void __user *arg,
                                 unsigned nr_args, u64 __user *tags)
@@ -8825,14 +8823,13 @@ static int io_sqe_files_register(struct io_ring_ctx *ctx, void __user *arg,
                        fput(file);
                        goto fail;
                }
-               file_slot = io_fixed_file_slot(&ctx->file_table, i);
-               io_fixed_file_set(file_slot, file);
-               ret = io_sqe_file_register(ctx, file, i);
+               ret = io_sqe_file_register(ctx, file);
                if (ret) {
-                       file_slot->file_ptr = 0;
                        fput(file);
                        goto fail;
                }
+               file_slot = io_fixed_file_slot(&ctx->file_table, i);
+               io_fixed_file_set(file_slot, file);
        }
 
        io_rsrc_node_switch(ctx, NULL);
@@ -8842,8 +8839,7 @@ fail:
        return ret;
 }
 
-static int io_sqe_file_register(struct io_ring_ctx *ctx, struct file *file,
-                               int index)
+static int io_sqe_file_register(struct io_ring_ctx *ctx, struct file *file)
 {
 #if defined(CONFIG_UNIX)
        struct sock *sock = ctx->ring_sock->sk;
@@ -8882,7 +8878,7 @@ static int io_sqe_file_register(struct io_ring_ctx *ctx, struct file *file,
                return 0;
        }
 
-       return __io_sqe_files_scm(ctx, index);
+       return __io_sqe_files_scm(ctx, file);
 #else
        return 0;
 #endif
@@ -8942,15 +8938,11 @@ static int io_install_fixed_file(struct io_kiocb *req, struct file *file,
                needs_switch = true;
        }
 
-       *io_get_tag_slot(ctx->file_data, slot_index) = 0;
-       io_fixed_file_set(file_slot, file);
-       ret = io_sqe_file_register(ctx, file, slot_index);
-       if (ret) {
-               file_slot->file_ptr = 0;
-               goto err;
+       ret = io_sqe_file_register(ctx, file);
+       if (!ret) {
+               *io_get_tag_slot(ctx->file_data, slot_index) = 0;
+               io_fixed_file_set(file_slot, file);
        }
-
-       ret = 0;
 err:
        if (needs_switch)
                io_rsrc_node_switch(ctx, ctx->file_data);
@@ -9061,14 +9053,13 @@ static int __io_sqe_files_update(struct io_ring_ctx *ctx,
                                err = -EBADF;
                                break;
                        }
-                       *io_get_tag_slot(data, i) = tag;
-                       io_fixed_file_set(file_slot, file);
-                       err = io_sqe_file_register(ctx, file, i);
+                       err = io_sqe_file_register(ctx, file);
                        if (err) {
-                               file_slot->file_ptr = 0;
                                fput(file);
                                break;
                        }
+                       *io_get_tag_slot(data, i) = tag;
+                       io_fixed_file_set(file_slot, file);
                }
        }