jcs.org
qemu with hax to log dma reads & writes
jcs.org/2018/11/12/vfio
block: Pass truncate exact=true where reasonable
This is a change in behavior, so all instances need a good
justification. The comments added here should explain my reasoning.
qed already had a comment that suggests it always expected
bdrv_truncate()/blk_truncate() to behave as if exact=true were passed
(c743849bee7 came eight months before 55b949c8476), so it was simply
broken until now.
Signed-off-by: Max Reitz <mreitz@redhat.com>
Message-id: 20190918095144.955-8-mreitz@redhat.com
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
[mreitz: Changed comment in qed.c to explain why a new QED file must be
empty, as requested and suggested by Maxim]
Signed-off-by: Max Reitz <mreitz@redhat.com>
+31
-7
+9
-2
block/parallels.c
+9
-2
block/parallels.c
···
487
487
res->leaks += count;
488
488
if (fix & BDRV_FIX_LEAKS) {
489
489
Error *local_err = NULL;
490
-
ret = bdrv_truncate(bs->file, res->image_end_offset, false,
490
+
491
+
/*
492
+
* In order to really repair the image, we must shrink it.
493
+
* That means we have to pass exact=true.
494
+
*/
495
+
ret = bdrv_truncate(bs->file, res->image_end_offset, true,
491
496
PREALLOC_MODE_OFF, &local_err);
492
497
if (ret < 0) {
493
498
error_report_err(local_err);
···
880
885
if ((bs->open_flags & BDRV_O_RDWR) && !(bs->open_flags & BDRV_O_INACTIVE)) {
881
886
s->header->inuse = 0;
882
887
parallels_update_header(bs);
883
-
bdrv_truncate(bs->file, s->data_end << BDRV_SECTOR_BITS, false,
888
+
889
+
/* errors are ignored, so we might as well pass exact=true */
890
+
bdrv_truncate(bs->file, s->data_end << BDRV_SECTOR_BITS, true,
884
891
PREALLOC_MODE_OFF, NULL);
885
892
}
886
893
+5
-1
block/qcow2.c
+5
-1
block/qcow2.c
···
5323
5323
return ret;
5324
5324
}
5325
5325
5326
-
ret = blk_truncate(blk, new_size, false, PREALLOC_MODE_OFF, errp);
5326
+
/*
5327
+
* Amending image options should ensure that the image has
5328
+
* exactly the given new values, so pass exact=true here.
5329
+
*/
5330
+
ret = blk_truncate(blk, new_size, true, PREALLOC_MODE_OFF, errp);
5327
5331
blk_unref(blk);
5328
5332
if (ret < 0) {
5329
5333
return ret;
+5
-2
block/qed.c
+5
-2
block/qed.c
···
673
673
674
674
l1_size = header.cluster_size * header.table_size;
675
675
676
-
/* File must start empty and grow, check truncate is supported */
677
-
ret = blk_truncate(blk, 0, false, PREALLOC_MODE_OFF, errp);
676
+
/*
677
+
* The QED format associates file length with allocation status,
678
+
* so a new file (which is empty) must have a length of 0.
679
+
*/
680
+
ret = blk_truncate(blk, 0, true, PREALLOC_MODE_OFF, errp);
678
681
if (ret < 0) {
679
682
goto out;
680
683
}
+6
-1
qemu-img.c
+6
-1
qemu-img.c
···
3831
3831
}
3832
3832
}
3833
3833
3834
-
ret = blk_truncate(blk, total_size, false, prealloc, &err);
3834
+
/*
3835
+
* The user expects the image to have the desired size after
3836
+
* resizing, so pass @exact=true. It is of no use to report
3837
+
* success when the image has not actually been resized.
3838
+
*/
3839
+
ret = blk_truncate(blk, total_size, true, prealloc, &err);
3835
3840
if (ret < 0) {
3836
3841
error_report_err(err);
3837
3842
goto out;
+6
-1
qemu-io-cmds.c
+6
-1
qemu-io-cmds.c
···
1710
1710
return offset;
1711
1711
}
1712
1712
1713
-
ret = blk_truncate(blk, offset, false, PREALLOC_MODE_OFF, &local_err);
1713
+
/*
1714
+
* qemu-io is a debugging tool, so let us be strict here and pass
1715
+
* exact=true. It is better to err on the "emit more errors" side
1716
+
* than to be overly permissive.
1717
+
*/
1718
+
ret = blk_truncate(blk, offset, true, PREALLOC_MODE_OFF, &local_err);
1714
1719
if (ret < 0) {
1715
1720
error_report_err(local_err);
1716
1721
return ret;