Re: [PATCH] Improve io_submit decoding

[Andi K. <ak...@li...>]

On Sun, Apr 10, 2011 at 01:32:55AM +0400, Dmitry V. Levin wrote:
> On Thu, Apr 07, 2011 at 10:07:15PM -0700, Andi Kleen wrote:
> > The io_submit handler didn't show a lot of the important information
> > in iocb passed to io_submit, like how much This patch improves this.
> 
> Thanks.  Would you like to write a commit message for the patch?

Here's an updated patch with ChangeLog.

---

Fix io_submit decoding in strace v2
    
strace didn't decode important fields in the iocb passed to io_submit.
This patch changes the code to dump them all. Also I prefixed the fields
with names to make it easier to read.
    
v2: Address review feedback. Use tprint_iov()/printstr() for write.
Add #warning for fallback.
    
* desc.c: (ARRAY_SIZE, iocb_cmd_lookup, print_common_flags): Add.
  (sys_io_submit): New iocb decoder.

diff --git a/desc.c b/desc.c
index 2b9f30a..6cd45a6 100644
--- a/desc.c
+++ b/desc.c
@@ -806,6 +806,51 @@ sys_io_destroy(struct tcb *tcp)
 	return 0;
 }
 
+#define ARRAY_SIZE(x) (sizeof(x)/sizeof(*(x)))
+
+enum iocb_sub {
+	SUB_NONE, SUB_COMMON, SUB_POLL, SUB_VECTOR
+};
+
+static const char *
+iocb_cmd_lookup(unsigned cmd, enum iocb_sub *sub)
+{
+	static char buf[20];
+	static struct {
+		const char *name;
+		enum iocb_sub sub;
+	} cmds[] = { 
+		{ "pread", SUB_COMMON },
+		{ "pwrite", SUB_COMMON },
+		{ "fsync", SUB_NONE },
+		{ "fdsync", SUB_NONE },
+		{ "op4", SUB_NONE },
+		{ "poll", SUB_POLL },
+		{ "noop", SUB_NONE },
+		{ "preadv", SUB_VECTOR },
+		{ "pwritev", SUB_VECTOR },
+	};
+
+	if (cmd < ARRAY_SIZE(cmds)) {
+		*sub = cmds[cmd].sub;
+		return cmds[cmd].name;
+	}
+	*sub = SUB_NONE;
+	snprintf(buf, sizeof buf, "?%u?", cmd); 
+	return buf;
+}
+
+/* Not defined in libaio.h */
+#define IOCB_RESFD (1 << 0)
+
+static void
+print_common_flags(struct iocb *iocb)
+{
+     if (iocb->u.c.flags & IOCB_RESFD)
+	     tprintf("resfd=%d, ", iocb->u.c.resfd);
+     if (iocb->u.c.flags & ~IOCB_RESFD)
+	     tprintf("flags=%x, ", iocb->u.c.flags);
+}
 int
 sys_io_submit(struct tcb *tcp)
 {
@@ -822,7 +867,9 @@ sys_io_submit(struct tcb *tcp)
 			struct iocb *iocbp, **iocbs = (void *)tcp->u_arg[2];
 
 			for (i = 0; i < nr; i++, iocbs++) {
+				enum iocb_sub sub;
 				struct iocb iocb;
+				int k;
 				if (i == 0)
 					tprintf("{");
 				else
@@ -833,14 +880,60 @@ sys_io_submit(struct tcb *tcp)
 					tprintf("{...}");
 					continue;
 				}
-				tprintf("{%p, %u, %hu, %hu, %d}",
-					iocb.data, iocb.key,
-					iocb.aio_lio_opcode,
-					iocb.aio_reqprio, iocb.aio_fildes);
+				tprintf("{");
+				if (iocb.data)
+					tprintf("data:%p, ", iocb.data);
+				if (iocb.key)
+					tprintf("key:%u, ", iocb.key);
+				tprintf("%s, ", iocb_cmd_lookup(iocb.aio_lio_opcode, &sub));
+				if (iocb.aio_reqprio)
+					tprintf("reqprio:%d, ", iocb.aio_reqprio);
+				tprintf("filedes:%d", iocb.aio_fildes);
+				switch (sub) {
+				case SUB_COMMON:
+					if (iocb.aio_lio_opcode == IO_CMD_PWRITE) {
+						tprintf(", str:");
+						printstr(tcp, (unsigned long)iocb.u.c.buf, 
+							 iocb.u.c.nbytes);
+					} else {
+						tprintf(", buf:%p", iocb.u.c.buf);
+					}
+					tprintf(", nbytes:%lu, offset:%llx", 
+						iocb.u.c.nbytes,
+						iocb.u.c.offset);
+					print_common_flags(&iocb);
+					break;
+				case SUB_VECTOR:
+					tprintf(", %llx, ", iocb.u.v.offset);
+					print_common_flags(&iocb);
+					if (iocb.aio_lio_opcode == IO_CMD_PWRITEV) {
+						tprint_iov(tcp, iocb.u.v.nr, (unsigned long)iocb.u.v.vec);
+						break;
+					}
+					for (k = 0; k < iocb.u.v.nr; k++) {
+						struct iovec iov;
+						tprintf("%s", k == 0 ? "" : ", ");
+						if (umove(tcp, (unsigned long)iocb.u.v.vec + 
+                                                                sizeof(struct iovec)*k, &iov))
+                                                        tprintf("[ ? ]");
+                                                else
+                                                        tprintf("[ %p, %lu ]", 
+                                                                iov.iov_base, 
+                                                                iov.iov_len);
+                                        }
+					break;
+				case SUB_POLL:
+					tprintf(", %x", iocb.u.poll.events);
+					break;
+				case SUB_NONE:
+				        break;
+				}
+				tprintf("}");
 			}
 			if (i)
 				tprintf("}");
 #else
+#warning "no io_submit decoding. install libaio-devel"
 			tprintf("{...}");
 #endif
 		}