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From:   Stefan Roesch <shr@fb.com>
To:     <io-uring@vger.kernel.org>, <kernel-team@fb.com>,
        <linux-mm@kvack.org>, <linux-xfs@vger.kernel.org>,
        <linux-fsdevel@vger.kernel.org>
CC:     <shr@fb.com>, <david@fromorbit.com>, <jack@suse.cz>,
        <hch@infradead.org>, <axboe@kernel.dk>
Subject: [PATCH v7 13/15] io_uring: Add tracepoint for short writes
Date:   Wed, 1 Jun 2022 14:01:39 -0700
Message-ID: <20220601210141.3773402-14-shr@fb.com>
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This adds the io_uring_short_write tracepoint to io_uring. A short write
is issued if not all pages that are required for a write are in the page
cache and the async buffered writes have to return EAGAIN.

Signed-off-by: Stefan Roesch <shr@fb.com>
---
 fs/io_uring.c                   |  3 +++
 include/trace/events/io_uring.h | 25 +++++++++++++++++++++++++
 2 files changed, 28 insertions(+)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index c0771e215669..9ab68138f442 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -4543,6 +4543,9 @@ static int io_write(struct io_kiocb *req, unsigned =
int issue_flags)
 		if (ret2 !=3D req->cqe.res && ret2 >=3D 0 && need_complete_io(req)) {
 			struct io_async_rw *rw;
=20
+			trace_io_uring_short_write(req->ctx, kiocb->ki_pos - ret2,
+						req->cqe.res, ret2);
+
 			/* This is a partial write. The file pos has already been
 			 * updated, setup the async struct to complete the request
 			 * in the worker. Also update bytes_done to account for
diff --git a/include/trace/events/io_uring.h b/include/trace/events/io_ur=
ing.h
index 66fcc5a1a5b1..25df513660cc 100644
--- a/include/trace/events/io_uring.h
+++ b/include/trace/events/io_uring.h
@@ -600,6 +600,31 @@ TRACE_EVENT(io_uring_cqe_overflow,
 		  __entry->cflags, __entry->ocqe)
 );
=20
+TRACE_EVENT(io_uring_short_write,
+
+	TP_PROTO(void *ctx, u64 fpos, u64 wanted, u64 got),
+
+	TP_ARGS(ctx, fpos, wanted, got),
+
+	TP_STRUCT__entry(
+		__field(void *,	ctx)
+		__field(u64,	fpos)
+		__field(u64,	wanted)
+		__field(u64,	got)
+	),
+
+	TP_fast_assign(
+		__entry->ctx	=3D ctx;
+		__entry->fpos	=3D fpos;
+		__entry->wanted	=3D wanted;
+		__entry->got	=3D got;
+	),
+
+	TP_printk("ring %p, fpos %lld, wanted %lld, got %lld",
+			  __entry->ctx, __entry->fpos,
+			  __entry->wanted, __entry->got)
+);
+
 #endif /* _TRACE_IO_URING_H */
=20
 /* This part must be outside protection */
--=20
2.30.2