io_uring/register: provide helper to get io_ring_ctx from 'fd'

Can be done in one of two ways:

1) Regular file descriptor, just fget()
2) Registered ring, index our own table for that

In preparation for adding another register use of needing to get a ctx
from a file descriptor, abstract out this helper and use it in the main
register syscall as well.

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

diff --git a/io_uring/register.c b/io_uring/register.c
index 57cb85c42526b0074bbfa5c8159e30f8b221770a..d90159478045c1a243ac6158b986cc7727aca2c9 100644 (file)
--- a/io_uring/register.c
+++ b/io_uring/register.c
@@ -550,21 +550,16 @@ static int __io_uring_register(struct io_ring_ctx *ctx, unsigned opcode,
        return ret;
 }
 
-SYSCALL_DEFINE4(io_uring_register, unsigned int, fd, unsigned int, opcode,
-               void __user *, arg, unsigned int, nr_args)
+/*
+ * Given an 'fd' value, return the ctx associated with if. If 'registered' is
+ * true, then the registered index is used. Otherwise, the normal fd table.
+ * Caller must call fput() on the returned file, unless it's an ERR_PTR.
+ */
+struct file *io_uring_register_get_file(int fd, bool registered)
 {
-       struct io_ring_ctx *ctx;
-       long ret = -EBADF;
        struct file *file;
-       bool use_registered_ring;
 
-       use_registered_ring = !!(opcode & IORING_REGISTER_USE_REGISTERED_RING);
-       opcode &= ~IORING_REGISTER_USE_REGISTERED_RING;
-
-       if (opcode >= IORING_REGISTER_LAST)
-               return -EINVAL;
-
-       if (use_registered_ring) {
+       if (registered) {
                /*
                 * Ring fd has been registered via IORING_REGISTER_RING_FDS, we
                 * need only dereference our task private array to find it.
@@ -572,27 +567,44 @@ SYSCALL_DEFINE4(io_uring_register, unsigned int, fd, unsigned int, opcode,
                struct io_uring_task *tctx = current->io_uring;
 
                if (unlikely(!tctx || fd >= IO_RINGFD_REG_MAX))
-                       return -EINVAL;
+                       return ERR_PTR(-EINVAL);
                fd = array_index_nospec(fd, IO_RINGFD_REG_MAX);
                file = tctx->registered_rings[fd];
-               if (unlikely(!file))
-                       return -EBADF;
        } else {
                file = fget(fd);
-               if (unlikely(!file))
-                       return -EBADF;
-               ret = -EOPNOTSUPP;
-               if (!io_is_uring_fops(file))
-                       goto out_fput;
        }
 
+       if (unlikely(!file))
+               return ERR_PTR(-EBADF);
+       if (io_is_uring_fops(file))
+               return file;
+       fput(file);
+       return ERR_PTR(-EOPNOTSUPP);
+}
+
+SYSCALL_DEFINE4(io_uring_register, unsigned int, fd, unsigned int, opcode,
+               void __user *, arg, unsigned int, nr_args)
+{
+       struct io_ring_ctx *ctx;
+       long ret = -EBADF;
+       struct file *file;
+       bool use_registered_ring;
+
+       use_registered_ring = !!(opcode & IORING_REGISTER_USE_REGISTERED_RING);
+       opcode &= ~IORING_REGISTER_USE_REGISTERED_RING;
+
+       if (opcode >= IORING_REGISTER_LAST)
+               return -EINVAL;
+
+       file = io_uring_register_get_file(fd, use_registered_ring);
+       if (IS_ERR(file))
+               return PTR_ERR(file);
        ctx = file->private_data;
 
        mutex_lock(&ctx->uring_lock);
        ret = __io_uring_register(ctx, opcode, arg, nr_args);
        mutex_unlock(&ctx->uring_lock);
        trace_io_uring_register(ctx, opcode, ctx->nr_user_files, ctx->nr_user_bufs, ret);
-out_fput:
        if (!use_registered_ring)
                fput(file);
        return ret;

diff --git a/io_uring/register.h b/io_uring/register.h
index c9da997d503c127a682a0829a69f4a1bc8a24956..cc69b88338fe3f685a0bf78ac0b55296be5b6b3e 100644 (file)
--- a/io_uring/register.h
+++ b/io_uring/register.h
@@ -4,5 +4,6 @@
 
 int io_eventfd_unregister(struct io_ring_ctx *ctx);
 int io_unregister_personality(struct io_ring_ctx *ctx, unsigned id);
+struct file *io_uring_register_get_file(int fd, bool registered);
 
 #endif