| Message ID | 20170413203401.3213-4-mreitz@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 04/13/2017 03:34 PM, Max Reitz wrote: > It does not make much sense to use a backing image for the target when > you concatenate multiple images (because then there is no correspondence > between the source images' backing files and the target's); but it was > still possible to give one by using -o backing_file=X instead of -B X. > > Fix this by moving the check. > > (Also, change the error message because -B is not the only way to > specify the backing file, evidently.) For that matter, 'create -B' is intentionally? undocumented in the qemu-img --help and man page. (Personally, I don't know why we don't want it documented - is it because it it not a universal option because not all formats support backing files?) > > Cc: qemu-stable <qemu-stable@nongnu.org> > Signed-off-by: Max Reitz <mreitz@redhat.com> > --- > qemu-img.c | 14 +++++++------- > tests/qemu-iotests/122.out | 4 ++-- > 2 files changed, 9 insertions(+), 9 deletions(-) > Reviewed-by: Eric Blake <eblake@redhat.com> Having a backing file for the destination may still make sense for some convoluted workflow, but you can get that with a followup qemu-img rebase.
On 13.04.2017 23:17, Eric Blake wrote: > On 04/13/2017 03:34 PM, Max Reitz wrote: >> It does not make much sense to use a backing image for the target when >> you concatenate multiple images (because then there is no correspondence >> between the source images' backing files and the target's); but it was >> still possible to give one by using -o backing_file=X instead of -B X. >> >> Fix this by moving the check. >> >> (Also, change the error message because -B is not the only way to >> specify the backing file, evidently.) > > For that matter, 'create -B' is intentionally? undocumented in the > qemu-img --help and man page. (Personally, I don't know why we don't > want it documented - is it because it it not a universal option because > not all formats support backing files?) (I suppose you mean convert instead of create) Well, the man page at least documents that you can use backing_file for the destination and what it will do. So documenting would probably be just "Oh, you can also use -B, by the way." I won't promise to write a patch to fix that, but I do hope I will. :-) >> Cc: qemu-stable <qemu-stable@nongnu.org> >> Signed-off-by: Max Reitz <mreitz@redhat.com> >> --- >> qemu-img.c | 14 +++++++------- >> tests/qemu-iotests/122.out | 4 ++-- >> 2 files changed, 9 insertions(+), 9 deletions(-) >> > > Reviewed-by: Eric Blake <eblake@redhat.com> Thanks, as always! Max > Having a backing file for the destination may still make sense for some > convoluted workflow, but you can get that with a followup qemu-img rebase.
diff --git a/qemu-img.c b/qemu-img.c index 70ffb07447..cfd1986efd 100644 --- a/qemu-img.c +++ b/qemu-img.c @@ -2113,13 +2113,6 @@ static int img_convert(int argc, char **argv) } - if (bs_n > 1 && out_baseimg) { - error_report("-B makes no sense when concatenating multiple input " - "images"); - ret = -1; - goto out; - } - src_flags = 0; ret = bdrv_parse_cache_mode(src_cache, &src_flags, &src_writethrough); if (ret < 0) { @@ -2229,6 +2222,13 @@ static int img_convert(int argc, char **argv) out_baseimg = out_baseimg_param; } + if (bs_n > 1 && out_baseimg) { + error_report("Having a backing file for the target makes no sense when " + "concatenating multiple input images"); + ret = -1; + goto out; + } + /* Check if compression is supported */ if (compress) { bool encryption = diff --git a/tests/qemu-iotests/122.out b/tests/qemu-iotests/122.out index 98814de5d6..9317d801ad 100644 --- a/tests/qemu-iotests/122.out +++ b/tests/qemu-iotests/122.out @@ -61,8 +61,8 @@ read 65536/65536 bytes at offset 4194304 64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec) read 65536/65536 bytes at offset 8388608 64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec) -qemu-img: -B makes no sense when concatenating multiple input images -qemu-img: -B makes no sense when concatenating multiple input images +qemu-img: Having a backing file for the target makes no sense when concatenating multiple input images +qemu-img: Having a backing file for the target makes no sense when concatenating multiple input images === Compression with misaligned allocations and image sizes ===
It does not make much sense to use a backing image for the target when you concatenate multiple images (because then there is no correspondence between the source images' backing files and the target's); but it was still possible to give one by using -o backing_file=X instead of -B X. Fix this by moving the check. (Also, change the error message because -B is not the only way to specify the backing file, evidently.) Cc: qemu-stable <qemu-stable@nongnu.org> Signed-off-by: Max Reitz <mreitz@redhat.com> --- qemu-img.c | 14 +++++++------- tests/qemu-iotests/122.out | 4 ++-- 2 files changed, 9 insertions(+), 9 deletions(-)