| Message ID | 20200402093603.2369-1-kwolf@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [for-5.0] vpc: Don't round up already aligned BAT sizes | expand |
On 4/2/20 11:36 AM, Kevin Wolf wrote: > As reported on Launchpad, Azure apparently doesn't accept images for > upload that are not both aligned to 1 MB blocks and have a BAT size that > matches the image size exactly. > > As far as I can tell, there is no real reason why we create a BAT that > is one entry longer than necessary for aligned image sizes, so change > that. > > (Even though the condition is only mentioned as "should" in the spec and > previous products accepted larger BATs - but we'll try to maintain > compatibility with as many of Microsoft's ever-changing interpretations > of the VHD spec as possible.) > > Fixes: https://bugs.launchpad.net/bugs/1870098 > Reported-by: Tobias Witek > Signed-off-by: Kevin Wolf <kwolf@redhat.com> > --- > block/vpc.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/block/vpc.c b/block/vpc.c > index 6df75e22dc..d8141b52da 100644 > --- a/block/vpc.c > +++ b/block/vpc.c > @@ -835,7 +835,7 @@ static int create_dynamic_disk(BlockBackend *blk, uint8_t *buf, > > /* Write the footer (twice: at the beginning and at the end) */ > block_size = 0x200000; > - num_bat_entries = (total_sectors + block_size / 512) / (block_size / 512); > + num_bat_entries = DIV_ROUND_UP(total_sectors, block_size / 512); > > ret = blk_pwrite(blk, offset, buf, HEADER_SIZE, 0); > if (ret < 0) { > Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
On 02.04.20 11:36, Kevin Wolf wrote: > As reported on Launchpad, Azure apparently doesn't accept images for > upload that are not both aligned to 1 MB blocks and have a BAT size that > matches the image size exactly. > > As far as I can tell, there is no real reason why we create a BAT that > is one entry longer than necessary for aligned image sizes, so change > that. > > (Even though the condition is only mentioned as "should" in the spec and > previous products accepted larger BATs - but we'll try to maintain > compatibility with as many of Microsoft's ever-changing interpretations > of the VHD spec as possible.) So as far as I can tell we still don’t ensure that the image is aligned to 1 MB blocks? Well, as long as it’s at least possible for the user to create valid images, that’s better. > Fixes: https://bugs.launchpad.net/bugs/1870098 > Reported-by: Tobias Witek > Signed-off-by: Kevin Wolf <kwolf@redhat.com> > --- > block/vpc.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/block/vpc.c b/block/vpc.c > index 6df75e22dc..d8141b52da 100644 > --- a/block/vpc.c > +++ b/block/vpc.c > @@ -835,7 +835,7 @@ static int create_dynamic_disk(BlockBackend *blk, uint8_t *buf, > > /* Write the footer (twice: at the beginning and at the end) */ > block_size = 0x200000; > - num_bat_entries = (total_sectors + block_size / 512) / (block_size / 512); > + num_bat_entries = DIV_ROUND_UP(total_sectors, block_size / 512); And the old code just looks like a wrong DIV_ROUND_UP() attempt. So: Reviewed-by: Max Reitz <mreitz@redhat.com> > > ret = blk_pwrite(blk, offset, buf, HEADER_SIZE, 0); > if (ret < 0) { >
Am 03.04.2020 um 10:55 hat Max Reitz geschrieben: > On 02.04.20 11:36, Kevin Wolf wrote: > > As reported on Launchpad, Azure apparently doesn't accept images for > > upload that are not both aligned to 1 MB blocks and have a BAT size that > > matches the image size exactly. > > > > As far as I can tell, there is no real reason why we create a BAT that > > is one entry longer than necessary for aligned image sizes, so change > > that. > > > > (Even though the condition is only mentioned as "should" in the spec and > > previous products accepted larger BATs - but we'll try to maintain > > compatibility with as many of Microsoft's ever-changing interpretations > > of the VHD spec as possible.) > > So as far as I can tell we still don’t ensure that the image is aligned > to 1 MB blocks? > > Well, as long as it’s at least possible for the user to create valid > images, that’s better. Yes, we still allow other image sizes because Azure is not the only product using VHD images, but it is the only one (to my knowledge) that makes this requirement. We're trying to stay compatible with at least three different Microsoft products (VirtualPC, HyperV, Azure) that all have their own interpretation of the spec and are inconsistent with each other. Kevin
On 03.04.20 14:04, Kevin Wolf wrote: > Am 03.04.2020 um 10:55 hat Max Reitz geschrieben: >> On 02.04.20 11:36, Kevin Wolf wrote: >>> As reported on Launchpad, Azure apparently doesn't accept images for >>> upload that are not both aligned to 1 MB blocks and have a BAT size that >>> matches the image size exactly. >>> >>> As far as I can tell, there is no real reason why we create a BAT that >>> is one entry longer than necessary for aligned image sizes, so change >>> that. >>> >>> (Even though the condition is only mentioned as "should" in the spec and >>> previous products accepted larger BATs - but we'll try to maintain >>> compatibility with as many of Microsoft's ever-changing interpretations >>> of the VHD spec as possible.) >> >> So as far as I can tell we still don’t ensure that the image is aligned >> to 1 MB blocks? >> >> Well, as long as it’s at least possible for the user to create valid >> images, that’s better. > > Yes, we still allow other image sizes because Azure is not the only > product using VHD images, but it is the only one (to my knowledge) that > makes this requirement. > > We're trying to stay compatible with at least three different Microsoft > products (VirtualPC, HyperV, Azure) that all have their own > interpretation of the spec and are inconsistent with each other. OK, nice. Thanks for the explanation! Max
diff --git a/block/vpc.c b/block/vpc.c index 6df75e22dc..d8141b52da 100644 --- a/block/vpc.c +++ b/block/vpc.c @@ -835,7 +835,7 @@ static int create_dynamic_disk(BlockBackend *blk, uint8_t *buf, /* Write the footer (twice: at the beginning and at the end) */ block_size = 0x200000; - num_bat_entries = (total_sectors + block_size / 512) / (block_size / 512); + num_bat_entries = DIV_ROUND_UP(total_sectors, block_size / 512); ret = blk_pwrite(blk, offset, buf, HEADER_SIZE, 0); if (ret < 0) {
As reported on Launchpad, Azure apparently doesn't accept images for upload that are not both aligned to 1 MB blocks and have a BAT size that matches the image size exactly. As far as I can tell, there is no real reason why we create a BAT that is one entry longer than necessary for aligned image sizes, so change that. (Even though the condition is only mentioned as "should" in the spec and previous products accepted larger BATs - but we'll try to maintain compatibility with as many of Microsoft's ever-changing interpretations of the VHD spec as possible.) Fixes: https://bugs.launchpad.net/bugs/1870098 Reported-by: Tobias Witek Signed-off-by: Kevin Wolf <kwolf@redhat.com> --- block/vpc.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)