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

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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>
This commit is contained in:
Jens Axboe 2024-09-12 09:29:29 -06:00
parent bfc0aa7a51
commit 0b6d253e08
2 changed files with 36 additions and 23 deletions
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58
io_uring/register.c
View File

@ -550,6 +550,38 @@ static int __io_uring_register(struct io_ring_ctx *ctx, unsigned opcode,
return ret;
}
/*
* 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 file *file;
if (registered) {
/*
* Ring fd has been registered via IORING_REGISTER_RING_FDS, we
* need only dereference our task private array to find it.
*/
struct io_uring_task *tctx = current->io_uring;
if (unlikely(!tctx || fd >= IO_RINGFD_REG_MAX))
return ERR_PTR(-EINVAL);
fd = array_index_nospec(fd, IO_RINGFD_REG_MAX);
file = tctx->registered_rings[fd];
} else {
file = fget(fd);
}
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)
{
@ -564,35 +596,15 @@ SYSCALL_DEFINE4(io_uring_register, unsigned int, fd, unsigned int, opcode,
if (opcode >= IORING_REGISTER_LAST)
return -EINVAL;
if (use_registered_ring) {
/*
* Ring fd has been registered via IORING_REGISTER_RING_FDS, we
* need only dereference our task private array to find it.
*/
struct io_uring_task *tctx = current->io_uring;
if (unlikely(!tctx || fd >= IO_RINGFD_REG_MAX))
return -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;
}
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;

1
io_uring/register.h
View File

@ -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