On 10/21/22 10:36, Stefan Metzmacher wrote:
Hi Pavel,
[...]
Right, I'm just tired of back porting patches by hand :)
ok, I just assumed it would be 6.1 only.
I'm fine with 6.1 only, it'd make things easier. I thought from
your first postings you wanted it 6.0. Then we don't need to care
about the placing of the copied/used flags.
Otherwise we could have IORING_CQE_F_COPIED by default without opt-in
flag...
Do you still want an opt-in flag to get IORING_CQE_F_COPIED?
If so what name do you want it to be?
Ala a IORING_SEND_* flag? Yes please.
*_REPORT_USAGE was fine but I'd make it IORING_SEND_ZC_REPORT_USAGE.
And can be extended if there is more info needed in the future.
And I don't mind using a bit in cqe->res, makes cflags less polluted.
+static void io_uring_tx_zerocopy_callback_report_usage(struct sk_buff *skb,
+ struct ubuf_info *uarg,
+ bool success)
+{
+ struct io_notif_data *nd = container_of(uarg, struct io_notif_data, uarg);
+
+ if (success && !nd->zc_used && skb)
+ nd->zc_used = true;
+ else if (unlikely(!success && !nd->zc_copied))
+ nd->zc_copied = true;
It's fine but racy, so let's WRITE_ONCE() to indicate it.
I don't see how this could be a problem, but I can add it.
It's not a problem, but better to be a little be more explicit
about parallel writes.
ok.
diff --git a/io_uring/notif.h b/io_uring/notif.h
index 5b4d710c8ca5..5ac7a2745e52 100644
--- a/io_uring/notif.h
+++ b/io_uring/notif.h
@@ -13,10 +13,12 @@ struct io_notif_data {
struct file *file;
struct ubuf_info uarg;
unsigned long account_pages;
+ bool zc_used;
+ bool zc_copied;
IIRC io_notif_data is fully packed in 6.1, so placing zc_{used,copied}
there might complicate backporting (if any). We can place them in io_kiocb
directly and move in 6.2. Alternatively account_pages doesn't have to be
long.
As far as I can see kernel-dk-block/io_uring-6.1 alread has your
shrink patches included...
Sorry, I mean 6.0
So you want to backport to 6.0?
Find the current version below, sizeof(struct io_kiocb) will grow from
3*64 + 24 to 3*64 + 32 (on x64_64) to it stays within 4 cache lines.
I tried this first:
union {
u8 iopoll_completed;
struct {
u8 zc_used:1;
u8 zc_copied:1;
};
};
But then WRITE_ONCE() complains about a bitfield write.
rightfully so, it can't be a bitfield as it would be racy
and not only in theory this time.
So let me now about the opt-in flag and I'll prepare real commits
including a patch that moves from struct io_kiocb to struct io_notif_data
on top.
Yeah, better to be opt-in, but apart from it and comments above
looks good.
diff --git a/include/linux/io_uring_types.h b/include/linux/io_uring_types.h
index f5b687a787a3..189152ad78d6 100644
--- a/include/linux/io_uring_types.h
+++ b/include/linux/io_uring_types.h
@@ -515,6 +515,9 @@ struct io_kiocb {
u8 opcode;
/* polled IO has completed */
u8 iopoll_completed;
+ /* these will be moved to struct io_notif_data in 6.1 */
+ bool zc_used;
+ bool zc_copied;
/*
* Can be either a fixed buffer index, or used with provided buffers.
* For the latter, before issue it points to the buffer group ID,
diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h
index ab7458033ee3..738d6234d1d9 100644
--- a/include/uapi/linux/io_uring.h
+++ b/include/uapi/linux/io_uring.h
@@ -350,6 +350,7 @@ struct io_uring_cqe {
#define IORING_CQE_F_MORE (1U << 1)
#define IORING_CQE_F_SOCK_NONEMPTY (1U << 2)
#define IORING_CQE_F_NOTIF (1U << 3)
+#define IORING_CQE_F_COPIED (1U << 4)
enum {
IORING_CQE_BUFFER_SHIFT = 16,
diff --git a/io_uring/notif.c b/io_uring/notif.c
index e37c6569d82e..033aca064b10 100644
--- a/io_uring/notif.c
+++ b/io_uring/notif.c
@@ -18,6 +18,10 @@ static void __io_notif_complete_tw(struct io_kiocb *notif, bool *locked)
__io_unaccount_mem(ctx->user, nd->account_pages);
nd->account_pages = 0;
}
+
+ if (notif->zc_copied || !notif->zc_used)
+ notif->cqe.flags |= IORING_CQE_F_COPIED;
+
As discussed above, should depend on IORING_SEND_ZC_REPORT_USAGE
io_req_task_complete(notif, locked);
}
@@ -28,6 +32,11 @@ static void io_uring_tx_zerocopy_callback(struct sk_buff *skb,
struct io_notif_data *nd = container_of(uarg, struct io_notif_data, uarg);
struct io_kiocb *notif = cmd_to_io_kiocb(nd);
+ if (success && !notif->zc_used && skb)
+ WRITE_ONCE(notif->zc_used, true);
+ else if (!success && !notif->zc_copied)
+ WRITE_ONCE(notif->zc_copied, true);
+
if (refcount_dec_and_test(&uarg->refcnt)) {
notif->io_task_work.func = __io_notif_complete_tw;
io_req_task_work_add(notif);
@@ -55,6 +64,7 @@ struct io_kiocb *io_alloc_notif(struct io_ring_ctx *ctx)
nd->account_pages = 0;
nd->uarg.flags = SKBFL_ZEROCOPY_FRAG | SKBFL_DONT_ORPHAN;
nd->uarg.callback = io_uring_tx_zerocopy_callback;
+ notif->zc_used = notif->zc_copied = false;
refcount_set(&nd->uarg.refcnt, 1);
return notif;
}
--
Pavel Begunkov
