在 2021/10/21 下午8:20, Pavel Begunkov 写道:
Another change to the API io-wq worker limitation API added in 5.15, apply the limit to all prior users that already registered a tctx. It may be confusing as it's now, in particular the change covers the following 2 cases: TASK1 | TASK2 _________________________________________________ ring = create() | | limit_iowq_workers() *not limited* | TASK1 | TASK2 _________________________________________________ ring = create() | | issue_requests() limit_iowq_workers() | | *not limited* A note on locking, it's safe to traverse ->tctx_list as we hold ->uring_lock, but do that after dropping sqd->lock to avoid possible problems. It's also safe to access tctx->io_wq there because tasks kill it only after removing themselves from tctx_list, see io_uring_cancel_generic() -> io_uring_clean_tctx() Signed-off-by: Pavel Begunkov <asml.silence@xxxxxxxxx> --- fs/io_uring.c | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) diff --git a/fs/io_uring.c b/fs/io_uring.c index d5cc103224f1..bc18af5e0a93 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -10649,7 +10649,9 @@ static int io_unregister_iowq_aff(struct io_ring_ctx *ctx)static int io_register_iowq_max_workers(struct io_ring_ctx *ctx,void __user *arg) + __must_hold(&ctx->uring_lock) { + struct io_tctx_node *node; struct io_uring_task *tctx = NULL; struct io_sq_data *sqd = NULL; __u32 new_count[2]; @@ -10702,6 +10704,22 @@ static int io_register_iowq_max_workers(struct io_ring_ctx *ctx, if (copy_to_user(arg, new_count, sizeof(new_count))) return -EFAULT;+ /* that's it for SQPOLL, only the SQPOLL task creates requests */+ if (sqd) + return 0; + + /* now propagate the restriction to all registered users */ + list_for_each_entry(node, &ctx->tctx_list, ctx_node) { + struct io_uring_task *tctx = node->task->io_uring; + + if (WARN_ON_ONCE(!tctx->io_wq)) + continue; + + for (i = 0; i < ARRAY_SIZE(new_count); i++) + new_count[i] = ctx->iowq_limits[i]; + /* ignore errors, it always returns zero anyway */ + (void)io_wq_max_workers(tctx->io_wq, new_count); + } return 0; err: if (sqd) {
Reviewed-by: Hao Xu <haoxu@xxxxxxxxxxxxxxxxx>
