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io_uring: move struct io_kiocb from task_struct to io_uring_task

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Rather than store the task_struct itself in struct io_kiocb, store
the io_uring specific task_struct. The life times are the same in terms
of io_uring, and this avoids doing some dereferences through the
task_struct. For the hot path of putting local task references, we can
deref req->tctx instead, which we'll need anyway in that function
regardless of whether it's local or remote references.

This is mostly straight forward, except the original task PF_EXITING
check needs a bit of tweaking. task_work is _always_ run from the
originating task, except in the fallback case, where it's run from a
kernel thread. Replace the potentially racy (in case of fallback work)
checks for req->task->flags with current->flags. It's either the still
the original task, in which case PF_EXITING will be sane, or it has
PF_KTHREAD set, in which case it's fallback work. Both cases should
prevent moving forward with the given request.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Jens Axboe
2024-11-03 10:23:38 -07:00
parent 6ed368cc5d
commit b6f58a3f4a
14 changed files with 48 additions and 36 deletions
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4
io_uring/msg_ring.c
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@@ -89,8 +89,8 @@ static void io_msg_tw_complete(struct io_kiocb *req, struct io_tw_state *ts)
static int io_msg_remote_post(struct io_ring_ctx *ctx, struct io_kiocb *req,
int res, u32 cflags, u64 user_data)
{
req->task = READ_ONCE(ctx->submitter_task);
if (!req->task) {
req->tctx = READ_ONCE(ctx->submitter_task->io_uring);
if (!req->tctx) {
kmem_cache_free(req_cachep, req);
return -EOWNERDEAD;
}