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io_uring: assign new io_identity for task if members have changed 

This avoids doing a copy for each new async IO, if some parts of the
io_identity has changed. We avoid reference counting for the normal
fast path of nothing ever changing.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Jens Axboe 2020-10-15 17:38:03 -06:00
parent 5c3462cfd1
commit 500a373d73
2 changed files with 17 additions and 5 deletions
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19
fs/io_uring.c
View File

@ -1066,12 +1066,18 @@ static void io_init_identity(struct io_identity *id)
*/
static inline void io_req_init_async(struct io_kiocb *req)
{
struct io_uring_task *tctx = current->io_uring;
if (req->flags & REQ_F_WORK_INITIALIZED)
return;
memset(&req->work, 0, sizeof(req->work));
req->flags |= REQ_F_WORK_INITIALIZED;
req->work.identity = &current->io_uring->identity;
/* Grab a ref if this isn't our static identity */
req->work.identity = tctx->identity;
if (tctx->identity != &tctx->__identity)
refcount_inc(&req->work.identity->count);
}
static inline bool io_async_submit(struct io_ring_ctx *ctx)
@ -1179,7 +1185,7 @@ static void __io_commit_cqring(struct io_ring_ctx *ctx)
static void io_put_identity(struct io_uring_task *tctx, struct io_kiocb *req)
{
if (req->work.identity == &tctx->identity)
if (req->work.identity == &tctx->__identity)
return;
if (refcount_dec_and_test(&req->work.identity->count))
kfree(req->work.identity);
@ -1254,11 +1260,12 @@ static bool io_identity_cow(struct io_kiocb *req)
refcount_inc(&id->count);
/* drop old identity, assign new one. one ref for req, one for tctx */
if (req->work.identity != &tctx->identity &&
if (req->work.identity != tctx->identity &&
refcount_sub_and_test(2, &req->work.identity->count))
kfree(req->work.identity);
req->work.identity = id;
tctx->identity = id;
return true;
}
@ -7691,7 +7698,8 @@ static int io_uring_alloc_task_context(struct task_struct *task)
tctx->in_idle = 0;
atomic_long_set(&tctx->req_issue, 0);
atomic_long_set(&tctx->req_complete, 0);
io_init_identity(&tctx->identity);
io_init_identity(&tctx->__identity);
tctx->identity = &tctx->__identity;
task->io_uring = tctx;
return 0;
}
@ -7701,6 +7709,9 @@ void __io_uring_free(struct task_struct *tsk)
struct io_uring_task *tctx = tsk->io_uring;
WARN_ON_ONCE(!xa_empty(&tctx->xa));
WARN_ON_ONCE(refcount_read(&tctx->identity->count) != 1);
if (tctx->identity != &tctx->__identity)
kfree(tctx->identity);
kfree(tctx);
tsk->io_uring = NULL;
}

3
include/linux/io_uring.h
View File

@ -24,7 +24,8 @@ struct io_uring_task {
struct wait_queue_head wait;
struct file *last;
atomic_long_t req_issue;
struct io_identity identity;
struct io_identity __identity;
struct io_identity *identity;
/* completion side */
bool in_idle ____cacheline_aligned_in_smp;