On 04/18/2018 09:25 AM, Vladimir Sementsov-Ogievskiy wrote:
>>> Do your code with
>>>
>>> /* Found an extent, and we're inside it. */
>>> *next = f.fe.fe_logical + f.fe.fe_length;
>>> if (f.fe.fe_flags & FIEMAP_EXTENT_UNWRITTEN) {
>>> return BDRV_BLOCK_DATA|BDRV_BLOCK_ZERO;
15.02.2018 19:42, Paolo Bonzini wrote:
On 15/02/2018 17:40, Vladimir Sementsov-Ogievskiy wrote:
Hi all.
Two years later, is there are any news on the topic?
I can't understand the following thing:
- FIEMAP without FLAG_SYNC is unsafe
- FIEMAP with FLAG_SYNC is safe but slow
- so, we've
On 15/02/2018 17:40, Vladimir Sementsov-Ogievskiy wrote:
> Hi all.
>
> Two years later, is there are any news on the topic?
>
> I can't understand the following thing:
>
> - FIEMAP without FLAG_SYNC is unsafe
> - FIEMAP with FLAG_SYNC is safe but slow
> - so, we've dropped FIEMAP and use only
Hi all.
Two years later, is there are any news on the topic?
I can't understand the following thing:
- FIEMAP without FLAG_SYNC is unsafe
- FIEMAP with FLAG_SYNC is safe but slow
- so, we've dropped FIEMAP and use only lseek. So, it means that lseek
is safe _and_ fast (at least, faster than
> > > i.e. the use of fiemap to duplicate the exact layout of a file
> > > from userspace is only posisble if you can /guarantee/ the source
> > > file has not changed in any way during the copy operation at the
> > > pointin time you finalise the destination data copy.
> >
> > We don't do exactly
On Thu, Jul 21, 2016 at 10:23:48AM -0400, Paolo Bonzini wrote:
> > > 1) avoid copying zero data, to keep the copy process efficient. For this,
> > > SEEK_HOLE/SEEK_DATA are enough.
> > >
> > > 2) copy file contents while preserving the allocation state of the file's
> > > extents.
> >
> > Which
> > 1) avoid copying zero data, to keep the copy process efficient. For this,
> > SEEK_HOLE/SEEK_DATA are enough.
> >
> > 2) copy file contents while preserving the allocation state of the file's
> > extents.
>
> Which is /very difficult/ to do safely and reliably.
> i.e. the use of fiemap to du
On Thu, Jul 21, 2016 at 01:31:21PM +0100, Pádraig Brady wrote:
> On 21/07/16 12:43, Dave Chinner wrote:
> > On Wed, Jul 20, 2016 at 03:35:17PM +0200, Niels de Vos wrote:
> >> Oh... And I was surprised to learn that "cp" does use FIEMAP and not
> >> SEEK_HOLE/SEEK_DATA. You give a strong suggestion
On 21/07/16 13:41, Dave Chinner wrote:
> On Wed, Jul 20, 2016 at 09:40:06AM -0400, Paolo Bonzini wrote:
1) is it expected that SEEK_HOLE skips unwritten extents?
>>>
>>> There are multiple answers to this, all of which are correct depending
>>> on current context and state:
>>>
>>> 1. No - som
On Wed, Jul 20, 2016 at 09:40:06AM -0400, Paolo Bonzini wrote:
> > > 1) is it expected that SEEK_HOLE skips unwritten extents?
> >
> > There are multiple answers to this, all of which are correct depending
> > on current context and state:
> >
> > 1. No - some filesystems will report clean unwrit
On 21/07/16 12:43, Dave Chinner wrote:
> On Wed, Jul 20, 2016 at 03:35:17PM +0200, Niels de Vos wrote:
>> On Wed, Jul 20, 2016 at 10:30:25PM +1000, Dave Chinner wrote:
>>> On Wed, Jul 20, 2016 at 05:19:37AM -0400, Paolo Bonzini wrote:
Adding ext4 and XFS guys (Lukas and Dave respectively). As
On Wed, Jul 20, 2016 at 03:35:17PM +0200, Niels de Vos wrote:
> On Wed, Jul 20, 2016 at 10:30:25PM +1000, Dave Chinner wrote:
> > On Wed, Jul 20, 2016 at 05:19:37AM -0400, Paolo Bonzini wrote:
> > > Adding ext4 and XFS guys (Lukas and Dave respectively). As a quick
> > > recap, the
> > > issue he
On Wed, Jul 20, 2016 at 10:30:25PM +1000, Dave Chinner wrote:
> On Wed, Jul 20, 2016 at 05:19:37AM -0400, Paolo Bonzini wrote:
> > Adding ext4 and XFS guys (Lukas and Dave respectively). As a quick recap,
> > the
> > issue here is the semantics of FIEMAP and SEEK_HOLE/SEEK_DATA, which we use
> >
On Wed, Jul 20, 2016 at 05:19:37AM -0400, Paolo Bonzini wrote:
> Adding ext4 and XFS guys (Lukas and Dave respectively). As a quick recap, the
> issue here is the semantics of FIEMAP and SEEK_HOLE/SEEK_DATA, which we use in
> "qemu-img map". This command prints metadata about a virtual disk
> im
> > 1) is it expected that SEEK_HOLE skips unwritten extents?
>
> There are multiple answers to this, all of which are correct depending
> on current context and state:
>
> 1. No - some filesystems will report clean unwritten extents as holes.
>
> 2. Yes - some filesystems will report clean unwr
Adding ext4 and XFS guys (Lukas and Dave respectively). As a quick recap, the
issue here is the semantics of FIEMAP and SEEK_HOLE/SEEK_DATA, which we use in
"qemu-img map". This command prints metadata about a virtual disk image---which
in the case of a raw image amounts to detecting holes and un
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