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io_uring: Support calling io_uring_register with a registered ring fd

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Add a new flag IORING_REGISTER_USE_REGISTERED_RING (set via the high bit
of the opcode) to treat the fd as a registered index rather than a file
descriptor.

This makes it possible for a library to open an io_uring, register the
ring fd, close the ring fd, and subsequently use the ring entirely via
registered index.

Signed-off-by: Josh Triplett <josh@joshtriplett.org>
Link: https://lore.kernel.org/r/f2396369e638284586b069dbddffb8c992afba95.1676419314.git.josh@joshtriplett.org
[axboe: remove extra high bit clear]
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Josh Triplett 2023-02-14 16:42:22 -08:00 committed by Jens Axboe
parent fbe870a72f
commit 7d3fd88d61
2 changed files with 31 additions and 8 deletions
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6
include/uapi/linux/io_uring.h
View file

@ -472,6 +472,7 @@ struct io_uring_params {
#define IORING_FEAT_RSRC_TAGS (1U << 10)
#define IORING_FEAT_CQE_SKIP (1U << 11)
#define IORING_FEAT_LINKED_FILE (1U << 12)
#define IORING_FEAT_REG_REG_RING (1U << 13)
/*
* io_uring_register(2) opcodes and arguments
@ -519,7 +520,10 @@ enum {
IORING_REGISTER_FILE_ALLOC_RANGE = 25,
/* this goes last */
IORING_REGISTER_LAST
IORING_REGISTER_LAST,
/* flag added to the opcode to use a registered ring fd */
IORING_REGISTER_USE_REGISTERED_RING = 1U << 31
};
/* io-wq worker categories */

33
io_uring/io_uring.c
View file

@ -3785,7 +3785,7 @@ static __cold int io_uring_create(unsigned entries, struct io_uring_params *p,
IORING_FEAT_POLL_32BITS | IORING_FEAT_SQPOLL_NONFIXED |
IORING_FEAT_EXT_ARG | IORING_FEAT_NATIVE_WORKERS |
IORING_FEAT_RSRC_TAGS | IORING_FEAT_CQE_SKIP |
IORING_FEAT_LINKED_FILE;
IORING_FEAT_LINKED_FILE | IORING_FEAT_REG_REG_RING;
if (copy_to_user(params, p, sizeof(*p))) {
ret = -EFAULT;
@ -4306,17 +4306,36 @@ SYSCALL_DEFINE4(io_uring_register, unsigned int, fd, unsigned int, opcode,
struct io_ring_ctx *ctx;
long ret = -EBADF;
struct fd f;
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;
f = fdget(fd);
if (!f.file)
return -EBADF;
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;
ret = -EOPNOTSUPP;
if (!io_is_uring_fops(f.file))
goto out_fput;
if (unlikely(!tctx || fd >= IO_RINGFD_REG_MAX))
return -EINVAL;
fd = array_index_nospec(fd, IO_RINGFD_REG_MAX);
f.file = tctx->registered_rings[fd];
f.flags = 0;
if (unlikely(!f.file))
return -EBADF;
} else {
f = fdget(fd);
if (unlikely(!f.file))
return -EBADF;
ret = -EOPNOTSUPP;
if (!io_is_uring_fops(f.file))
goto out_fput;
}
ctx = f.file->private_data;