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io_uring: allow allocated fixed files for openat/openat2

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If the application passes in IORING_FILE_INDEX_ALLOC as the file_slot,
then that's a hint to allocate a fixed file descriptor rather than have
one be passed in directly.

This can be useful for having io_uring manage the direct descriptor space.

Normal open direct requests will complete with 0 for success, and < 0
in case of error. If io_uring is asked to allocated the direct descriptor,
then the direct descriptor is returned in case of success.

Reviewed-by: Hao Xu <howeyxu@tencent.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Jens Axboe
2022-05-07 14:18:44 -06:00
parent b70b8e3331
commit 1339f24b33
2 changed files with 42 additions and 3 deletions
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9
include/uapi/linux/io_uring.h
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@@ -63,6 +63,15 @@ struct io_uring_sqe {
__u64 __pad2[2];
};
/*
* If sqe->file_index is set to this for opcodes that instantiate a new
* direct descriptor (like openat/openat2/accept), then io_uring will allocate
* an available direct descriptor instead of having the application pass one
* in. The picked direct descriptor will be returned in cqe->res, or -ENFILE
* if the space is full.
*/
#define IORING_FILE_INDEX_ALLOC (~0U)
enum {
IOSQE_FIXED_FILE_BIT,
IOSQE_IO_DRAIN_BIT,