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Subject[PATCH v2 1/3] io_uring: register single issuer task at creation
Date
Instead of picking the task from the first submitter task, rather use the
creator task or in the case of disabled (IORING_SETUP_R_DISABLED) the
enabling task.

This approach allows a lot of simplification of the logic here. This
removes init logic from the submission path, which can always be a bit
confusing, but also removes the need for locking to write (or read) the
submitter_task.

Users that want to move a ring before submitting can create the ring
disabled and then enable it on the submitting task.

Signed-off-by: Dylan Yudaken <dylany@fb.com>
---
io_uring/io_uring.c | 7 +++++++
1 file changed, 7 insertions(+)

diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
index 2965b354efc8..242d896c00f3 100644
--- a/io_uring/io_uring.c
+++ b/io_uring/io_uring.c
@@ -3357,6 +3357,10 @@ static __cold int io_uring_create(unsigned entries, struct io_uring_params *p,
goto err;
}

+ if (ctx->flags & IORING_SETUP_SINGLE_ISSUER
+ && !(ctx->flags & IORING_SETUP_R_DISABLED))
+ ctx->submitter_task = get_task_struct(current);
+
file = io_uring_get_file(ctx);
if (IS_ERR(file)) {
ret = PTR_ERR(file);
@@ -3548,6 +3552,9 @@ static int io_register_enable_rings(struct io_ring_ctx *ctx)
if (!(ctx->flags & IORING_SETUP_R_DISABLED))
return -EBADFD;

+ if (ctx->flags & IORING_SETUP_SINGLE_ISSUER && !ctx->submitter_task)
+ ctx->submitter_task = get_task_struct(current);
+
if (ctx->restrictions.registered)
ctx->restricted = 1;

--
2.30.2
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