From: "Charles Coffing" <ccoffing@novell.com>
Subject: [PATCH] hang in qcow2raw
Date: Fri, 30 Mar 2007 15:37:41 -0400
Message-ID: <460D11D4.D169.003C.0@novell.com>
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Hi, 

We hit a bug in which qcow2raw would hang the conversion just short of 100%, because the final write queue was never being submitted.  If a blktap drivers read synchronously, then "submit_events" and "complete" variables are checked before getting set, so the fact that reads have finished is not noticed, so the final write queue was never submitted.

Note that I have also removed the variables write_complete and read_complete.  They were unused, and they were also not set correctly in the synchronous case.

Patch attached; please apply to xen-unstable.

Thanks.

Signed-off-by: Charles Coffing <ccoffing@novell.com>


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--- a/tools/blktap/drivers/qcow2raw.c	2007-03-12 09:01:04.000000000 =
-0600
+++ b/tools/blktap/drivers/qcow2raw.c	2007-03-30 13:07:57.000000000 =
-0600
@@ -51,7 +51,6 @@
 #define BLOCK_PROCESSSZ 4096
=20
 static int maxfds, *qcowio_fd, *aio_fd, running =3D 1, complete =3D 0;=20
-static int read_complete =3D 0, write_complete =3D 0;
 static int returned_read_events =3D 0, returned_write_events =3D 0;
 static int submit_events =3D 0;
 static uint32_t read_idx =3D 0, write_idx =3D 0;
@@ -109,8 +108,6 @@
 	written +=3D BLOCK_PROCESSSZ;
 	returned_write_events++;
 	write_idx =3D idx;
-	if (complete && (returned_write_events =3D=3D submit_events))=20
-		write_complete =3D 1;
=20
 	debug_output(written, dd->td_state->size << 9);
 	free(private);
@@ -126,8 +123,6 @@
 =09
 	returned_read_events++;
 	read_idx =3D idx;
-	if (complete && (returned_read_events =3D=3D submit_events))=20
-		read_complete =3D 1;
 =09
 	ret =3D ddaio.drv->td_queue_write(&ddaio, idx, BLOCK_PROCESSSZ>>9, =
private,=20
 					send_write_responses, idx, =
private);
@@ -136,7 +131,7 @@
 		return 0;
 	}
=20
-	if ( (complete && returned_read_events =3D=3D submit_events) ||=20
+	if ( (returned_read_events =3D=3D submit_events) ||=20
 	     (returned_read_events % 10 =3D=3D 0) ) {
 		ddaio.drv->td_submit(&ddaio);
 	}
@@ -299,6 +294,7 @@
 			}
 	=09
 			/*Attempt to read 4k sized blocks*/
+			submit_events++;
 			ret =3D ddqcow.drv->td_queue_read(&ddqcow, i>>9,
 							BLOCK_PROCESSSZ>>9,=
 buf,=20
 							send_read_responses=
, i>>9, buf);
@@ -309,7 +305,6 @@
 				exit(-1);
 			} else {
 				i +=3D BLOCK_PROCESSSZ;
-				submit_events++;
 			}
=20
 			if (i >=3D ddqcow.td_state->size<<9) {

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