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authorPavel Begunkov <asml.silence@gmail.com>2021-10-21 13:20:29 +0100
committerJens Axboe <axboe@kernel.dk>2021-10-21 11:19:38 -0600
commitb22fa62a35d7f2029d757a518d78041822b7c7c1 (patch)
tree610af96d64a830b4b5fae86a0f4cffd692a85ad8 /fs
parent4ea672ab694c23886b52e97cee10dea056e43e62 (diff)
downloadlwn-b22fa62a35d7f2029d757a518d78041822b7c7c1.tar.gz
lwn-b22fa62a35d7f2029d757a518d78041822b7c7c1.zip
io_uring: apply worker limits to previous users
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@gmail.com> Link: https://lore.kernel.org/r/d6e09ecc3545e4dc56e43c906ee3d71b7ae21bed.1634818641.git.asml.silence@gmail.com Reviewed-by: Hao Xu <haoxu@linux.alibaba.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'fs')
-rw-r--r--fs/io_uring.c18
1 files changed, 18 insertions, 0 deletions
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) {