From b4ccc4dd1330a4d0db6aa4c6781631d1bab76c45 Mon Sep 17 00:00:00 2001
From: Jens Axboe <axboe@kernel.dk>
Date: Thu, 15 Feb 2024 15:30:33 -0700
Subject: [PATCH] io_uring/napi: enable even with a timeout of 0
1 usec is not as short as it used to be, and it makes sense to allow 0
for a busy poll timeout - this means just do one loop to check if we
have anything available. Add a separate ->napi_enabled to check if napi
has been enabled or not.
While at it, move the writing of the ctx napi values after we've copied
the old values back to userspace. This ensures that if the call fails,
we'll be in the same state as we were before, rather than some
indeterminate state.
Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
include/linux/io_uring_types.h | 1 +
io_uring/napi.c | 9 +++++----
2 files changed, 6 insertions(+), 4 deletions(-)
diff --git a/include/linux/io_uring_types.h b/include/linux/io_uring_types.h
index 4fe7af8a49078..bd7071aeec5d0 100644
--- a/include/linux/io_uring_types.h
+++ b/include/linux/io_uring_types.h
@@ -420,6 +420,7 @@ struct io_ring_ctx {
/* napi busy poll default timeout */
unsigned int napi_busy_poll_to;
bool napi_prefer_busy_poll;
+ bool napi_enabled;
DECLARE_HASHTABLE(napi_ht, 4);
#endif
diff --git a/io_uring/napi.c b/io_uring/napi.c
index b234adda7dfd2..883a1a6659075 100644
--- a/io_uring/napi.c
+++ b/io_uring/napi.c
@@ -227,12 +227,12 @@ int io_register_napi(struct io_ring_ctx *ctx, void __user *arg)
if (napi.pad[0] || napi.pad[1] || napi.pad[2] || napi.resv)
return -EINVAL;
- WRITE_ONCE(ctx->napi_busy_poll_to, napi.busy_poll_to);
- WRITE_ONCE(ctx->napi_prefer_busy_poll, !!napi.prefer_busy_poll);
-
if (copy_to_user(arg, &curr, sizeof(curr)))
return -EFAULT;
+ WRITE_ONCE(ctx->napi_busy_poll_to, napi.busy_poll_to);
+ WRITE_ONCE(ctx->napi_prefer_busy_poll, !!napi.prefer_busy_poll);
+ WRITE_ONCE(ctx->napi_enabled, true);
return 0;
}
@@ -256,6 +256,7 @@ int io_unregister_napi(struct io_ring_ctx *ctx, void __user *arg)
WRITE_ONCE(ctx->napi_busy_poll_to, 0);
WRITE_ONCE(ctx->napi_prefer_busy_poll, false);
+ WRITE_ONCE(ctx->napi_enabled, false);
return 0;
}
@@ -300,7 +301,7 @@ void __io_napi_busy_loop(struct io_ring_ctx *ctx, struct io_wait_queue *iowq)
{
iowq->napi_prefer_busy_poll = READ_ONCE(ctx->napi_prefer_busy_poll);
- if (!(ctx->flags & IORING_SETUP_SQPOLL) && iowq->napi_busy_poll_to)
+ if (!(ctx->flags & IORING_SETUP_SQPOLL) && ctx->napi_enabled)
io_napi_blocking_busy_loop(ctx, iowq);
}
--
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