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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
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

36
fs/io_uring.c
View file

@ -4697,7 +4697,7 @@ static int io_openat2_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
return __io_openat_prep(req, sqe);
}
static int __maybe_unused io_file_bitmap_get(struct io_ring_ctx *ctx)
static int io_file_bitmap_get(struct io_ring_ctx *ctx)
{
struct io_file_table *table = &ctx->file_table;
unsigned long nr = ctx->nr_user_files;
@ -4722,6 +4722,36 @@ static int __maybe_unused io_file_bitmap_get(struct io_ring_ctx *ctx)
return -ENFILE;
}
static int io_fixed_fd_install(struct io_kiocb *req, unsigned int issue_flags,
struct file *file, unsigned int file_slot)
{
bool alloc_slot = file_slot == IORING_FILE_INDEX_ALLOC;
struct io_ring_ctx *ctx = req->ctx;
int ret;
if (alloc_slot) {
io_ring_submit_lock(ctx, issue_flags);
ret = io_file_bitmap_get(ctx);
if (unlikely(ret < 0)) {
io_ring_submit_unlock(ctx, issue_flags);
return ret;
}
file_slot = ret;
} else {
file_slot--;
}
ret = io_install_fixed_file(req, file, issue_flags, file_slot);
if (alloc_slot) {
io_ring_submit_unlock(ctx, issue_flags);
if (!ret)
return file_slot;
}
return ret;
}
static int io_openat2(struct io_kiocb *req, unsigned int issue_flags)
{
struct open_flags op;
@ -4777,8 +4807,8 @@ static int io_openat2(struct io_kiocb *req, unsigned int issue_flags)
if (!fixed)
fd_install(ret, file);
else
ret = io_install_fixed_file(req, file, issue_flags,
req->open.file_slot - 1);
ret = io_fixed_fd_install(req, issue_flags, file,
req->open.file_slot);
err:
putname(req->open.filename);
req->flags &= ~REQ_F_NEED_CLEANUP;

9
include/uapi/linux/io_uring.h
View file

@ -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,