2022-07-12 20:57:58

by Pavel Begunkov

Subject: [PATCH net-next v5 17/27] io_uring: add rsrc referencing for notifiers

In preparation to zerocopy sends with fixed buffers make notifiers to
reference the rsrc node to protect the used fixed buffers. We can't just
grab it for a send request as notifiers can likely outlive requests that
used it.

Signed-off-by: Pavel Begunkov <[email protected]>
---
io_uring/notif.c | 5 +++++
io_uring/notif.h | 1 +
io_uring/rsrc.h | 12 +++++++++---
3 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/io_uring/notif.c b/io_uring/notif.c
index aec74f88fc33..0a2e98bd74f6 100644
--- a/io_uring/notif.c
+++ b/io_uring/notif.c
@@ -7,10 +7,12 @@

#include "io_uring.h"
#include "notif.h"
+#include "rsrc.h"

static void __io_notif_complete_tw(struct callback_head *cb)
{
struct io_notif *notif = container_of(cb, struct io_notif, task_work);
+ struct io_rsrc_node *rsrc_node = notif->rsrc_node;
struct io_ring_ctx *ctx = notif->ctx;

if (likely(notif->task)) {
@@ -25,6 +27,7 @@ static void __io_notif_complete_tw(struct callback_head *cb)
ctx->notif_locked_nr++;
io_cq_unlock_post(ctx);

+ io_rsrc_put_node(rsrc_node, 1);
percpu_ref_put(&ctx->refs);
}

@@ -119,6 +122,8 @@ struct io_notif *io_alloc_notif(struct io_ring_ctx *ctx,
/* master ref owned by io_notif_slot, will be dropped on flush */
refcount_set(&notif->uarg.refcnt, 1);
percpu_ref_get(&ctx->refs);
+ notif->rsrc_node = ctx->rsrc_node;
+ io_charge_rsrc_node(ctx);
return notif;
}

diff --git a/io_uring/notif.h b/io_uring/notif.h
index 23ca7620fff9..1dd48efb7744 100644
--- a/io_uring/notif.h
+++ b/io_uring/notif.h
@@ -10,6 +10,7 @@
struct io_notif {
struct ubuf_info uarg;
struct io_ring_ctx *ctx;
+ struct io_rsrc_node *rsrc_node;

/* complete via tw if ->task is non-NULL, fallback to wq otherwise */
struct task_struct *task;
diff --git a/io_uring/rsrc.h b/io_uring/rsrc.h
index 87f58315b247..af342fd239d0 100644
--- a/io_uring/rsrc.h
+++ b/io_uring/rsrc.h
@@ -135,6 +135,13 @@ static inline void io_req_put_rsrc_locked(struct io_kiocb *req,
}
}

+static inline void io_charge_rsrc_node(struct io_ring_ctx *ctx)
+{
+ ctx->rsrc_cached_refs--;
+ if (unlikely(ctx->rsrc_cached_refs < 0))
+ io_rsrc_refs_refill(ctx);
+}
+
static inline void io_req_set_rsrc_node(struct io_kiocb *req,
struct io_ring_ctx *ctx,
unsigned int issue_flags)
@@ -144,9 +151,8 @@ static inline void io_req_set_rsrc_node(struct io_kiocb *req,

if (!(issue_flags & IO_URING_F_UNLOCKED)) {
lockdep_assert_held(&ctx->uring_lock);
- ctx->rsrc_cached_refs--;
- if (unlikely(ctx->rsrc_cached_refs < 0))
- io_rsrc_refs_refill(ctx);
+
+ io_charge_rsrc_node(ctx);
} else {
percpu_ref_get(&req->rsrc_node->refs);
}
--
2.37.0