[PATCHSET 0/3] Free request caches for exiting task

[PATCHSET 0/3] Free request caches for exiting task

[Jens Axboe]

Hi,

Now that we account these requests, on the off chance that we're sharing
the ring, be nice and prune caches belonging to an exiting task.

Two prep patches to get there, final one-liner hooks it up.

-- 
Jens Axboe

[PATCH 1/3] io_uring: allow task match to be passed to io_req_cache_free()

[Jens Axboe]

No changes in this patch, just allows a caller to pass in a targeted
task that we must match for freeing requests in the cache.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
 fs/io_uring.c | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 2e8cb739c835..9cd7b03a6f34 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -8681,12 +8681,13 @@ static void io_destroy_buffers(struct io_ring_ctx *ctx)
 	idr_destroy(&ctx->io_buffer_idr);
 }
 
-static void io_req_cache_free(struct list_head *list)
+static void io_req_cache_free(struct list_head *list, struct task_struct *tsk)
 {
-	while (!list_empty(list)) {
-		struct io_kiocb *req;
+	struct io_kiocb *req, *nxt;
 
-		req = list_first_entry(list, struct io_kiocb, compl.list);
+	list_for_each_entry_safe(req, nxt, list, compl.list) {
+		if (tsk && req->task != tsk)
+			continue;
 		list_del(&req->compl.list);
 		kmem_cache_free(req_cachep, req);
 	}
@@ -8742,8 +8743,8 @@ static void io_ring_ctx_free(struct io_ring_ctx *ctx)
 	free_uid(ctx->user);
 	put_cred(ctx->creds);
 	kfree(ctx->cancel_hash);
-	io_req_cache_free(&ctx->submit_state.comp.free_list);
-	io_req_cache_free(&ctx->submit_state.comp.locked_free_list);
+	io_req_cache_free(&ctx->submit_state.comp.free_list, NULL);
+	io_req_cache_free(&ctx->submit_state.comp.locked_free_list, NULL);
 	kfree(ctx);
 }
 
-- 
2.30.0

[PATCH 2/3] io_uring: add helper to free all request caches

[Jens Axboe]

We have three different ones, put it in a helper for easy calling. This
is in preparation for doing it outside of ring freeing as well. With
that in mind, also ensure that we do the proper locking for safe calling
from a context where the ring it still live.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
 fs/io_uring.c | 26 +++++++++++++++++++-------
 1 file changed, 19 insertions(+), 7 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 9cd7b03a6f34..1895fc132252 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -8693,10 +8693,27 @@ static void io_req_cache_free(struct list_head *list, struct task_struct *tsk)
 	}
 }
 
-static void io_ring_ctx_free(struct io_ring_ctx *ctx)
+static void io_req_caches_free(struct io_ring_ctx *ctx, struct task_struct *tsk)
 {
 	struct io_submit_state *submit_state = &ctx->submit_state;
 
+	mutex_lock(&ctx->uring_lock);
+
+	if (submit_state->free_reqs)
+		kmem_cache_free_bulk(req_cachep, submit_state->free_reqs,
+				     submit_state->reqs);
+
+	io_req_cache_free(&submit_state->comp.free_list, NULL);
+
+	spin_lock_irq(&ctx->completion_lock);
+	io_req_cache_free(&submit_state->comp.locked_free_list, NULL);
+	spin_unlock_irq(&ctx->completion_lock);
+
+	mutex_unlock(&ctx->uring_lock);
+}
+
+static void io_ring_ctx_free(struct io_ring_ctx *ctx)
+{
 	/*
 	 * Some may use context even when all refs and requests have been put,
 	 * and they are free to do so while still holding uring_lock, see
@@ -8715,10 +8732,6 @@ static void io_ring_ctx_free(struct io_ring_ctx *ctx)
 		ctx->mm_account = NULL;
 	}
 
-	if (submit_state->free_reqs)
-		kmem_cache_free_bulk(req_cachep, submit_state->free_reqs,
-				     submit_state->reqs);
-
 #ifdef CONFIG_BLK_CGROUP
 	if (ctx->sqo_blkcg_css)
 		css_put(ctx->sqo_blkcg_css);
@@ -8742,9 +8755,8 @@ static void io_ring_ctx_free(struct io_ring_ctx *ctx)
 	percpu_ref_exit(&ctx->refs);
 	free_uid(ctx->user);
 	put_cred(ctx->creds);
+	io_req_caches_free(ctx, NULL);
 	kfree(ctx->cancel_hash);
-	io_req_cache_free(&ctx->submit_state.comp.free_list, NULL);
-	io_req_cache_free(&ctx->submit_state.comp.locked_free_list, NULL);
 	kfree(ctx);
 }
 
-- 
2.30.0

[PATCH 3/3] io_uring: kill cached requests from exiting task closing the ring

[Jens Axboe]

Be nice and prune these upfront, in case the ring is being shared and
one of the tasks is going away. This is a bit more important now that
we account the allocations.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
 fs/io_uring.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 1895fc132252..a9d094f7060f 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -9232,8 +9232,10 @@ static int io_uring_flush(struct file *file, void *data)
 	struct io_uring_task *tctx = current->io_uring;
 	struct io_ring_ctx *ctx = file->private_data;
 
-	if (fatal_signal_pending(current) || (current->flags & PF_EXITING))
+	if (fatal_signal_pending(current) || (current->flags & PF_EXITING)) {
 		io_uring_cancel_task_requests(ctx, NULL);
+		io_req_caches_free(ctx, current);
+	}
 
 	if (!tctx)
 		return 0;
-- 
2.30.0