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Re: [Qemu-devel] [PATCH v5 13/14] nbd: Implement NBD_CMD_WRITE_ZEROES on
From: |
Paolo Bonzini |
Subject: |
Re: [Qemu-devel] [PATCH v5 13/14] nbd: Implement NBD_CMD_WRITE_ZEROES on server |
Date: |
Wed, 20 Jul 2016 04:16:28 -0400 (EDT) |
> On Wed, 07/20 09:09, Paolo Bonzini wrote:
> > On 20/07/2016 06:37, Fam Zheng wrote:
> > > Yes, you are right about this, I was confused because "qemu-img map" does
> > > not
> > > report this allocation state after zero write. (No idea why SEEK_DATA
> > > doesn't
> > > hit the fallocate'ed area.)
> >
> > Apparently it's because it's zeroed.
> >
> > $ fallocate -z -o 10485760 -l 10485760 test
> > $ fallocate -p -o 49152000 -l 10485760 test
> > $ fallocate -o 49152000 -l 10485760 test
> > $ fallocate -p -o 65536000 -l 10485760 test
> >
> > Now we have:
> >
> > - a zero area at 10240K..20480K
> >
> > - an hole+allocated area at 48000K..59240K
> >
> > - a hole at 64000K..74240K
> >
> > $ qemu-img map test
> > Offset Length Mapped to File
> > 0 0xa00000 0 test << ends at 10240K
> > 0x1400000 0x1ae0000 0x1400000 test << ends at 48000K
> > 0x38e0000 0x5a0000 0x38e0000 test << ends at 64000K
> > 0x4880000 0x1b80000 0x4880000 test
>
> Hah? I'm apparently missing something. I can't see these entries:
>
> > address@hidden:/var/tmp$ cat /tmp/sh
> > touch test
> > fallocate -z -o 10485760 -l 10485760 test
> > fallocate -p -o 49152000 -l 10485760 test
> > fallocate -o 49152000 -l 10485760 test
> > fallocate -p -o 65536000 -l 10485760 test
> > qemu-img map test
> > address@hidden:/var/tmp$ sh /tmp/sh
> > Offset Length Mapped to File
>
> (I'm using Fedora 24 but I've also tried RHEL 7.)
That was after a full allocation of a 1GB file. I didn't copy that line
because I had the file lying around from another day--sorry.
Paolo
- [Qemu-devel] [PATCH v5 03/14] nbd: Limit nbdflags to 16 bits, (continued)
- [Qemu-devel] [PATCH v5 03/14] nbd: Limit nbdflags to 16 bits, Eric Blake, 2016/07/19
- [Qemu-devel] [PATCH v5 13/14] nbd: Implement NBD_CMD_WRITE_ZEROES on server, Eric Blake, 2016/07/19
- Re: [Qemu-devel] [PATCH v5 13/14] nbd: Implement NBD_CMD_WRITE_ZEROES on server, Fam Zheng, 2016/07/19
- Re: [Qemu-devel] [PATCH v5 13/14] nbd: Implement NBD_CMD_WRITE_ZEROES on server, Eric Blake, 2016/07/19
- Re: [Qemu-devel] [PATCH v5 13/14] nbd: Implement NBD_CMD_WRITE_ZEROES on server, Paolo Bonzini, 2016/07/19
- Re: [Qemu-devel] [PATCH v5 13/14] nbd: Implement NBD_CMD_WRITE_ZEROES on server, Fam Zheng, 2016/07/19
- Re: [Qemu-devel] [PATCH v5 13/14] nbd: Implement NBD_CMD_WRITE_ZEROES on server, Eric Blake, 2016/07/19
- Re: [Qemu-devel] [PATCH v5 13/14] nbd: Implement NBD_CMD_WRITE_ZEROES on server, Fam Zheng, 2016/07/20
- Re: [Qemu-devel] [PATCH v5 13/14] nbd: Implement NBD_CMD_WRITE_ZEROES on server, Paolo Bonzini, 2016/07/20
- Re: [Qemu-devel] [PATCH v5 13/14] nbd: Implement NBD_CMD_WRITE_ZEROES on server, Fam Zheng, 2016/07/20
- Re: [Qemu-devel] [PATCH v5 13/14] nbd: Implement NBD_CMD_WRITE_ZEROES on server,
Paolo Bonzini <=
- Re: [Qemu-devel] [PATCH v5 13/14] nbd: Implement NBD_CMD_WRITE_ZEROES on server, Fam Zheng, 2016/07/20
- [Qemu-devel] semantics of FIEMAP without FIEMAP_FLAG_SYNC (was Re: [PATCH v5 13/14] nbd: Implement NBD_CMD_WRITE_ZEROES on server), Paolo Bonzini, 2016/07/20
- Re: [Qemu-devel] semantics of FIEMAP without FIEMAP_FLAG_SYNC (was Re: [PATCH v5 13/14] nbd: Implement NBD_CMD_WRITE_ZEROES on server), Dave Chinner, 2016/07/20
- Re: [Qemu-devel] semantics of FIEMAP without FIEMAP_FLAG_SYNC (was Re: [PATCH v5 13/14] nbd: Implement NBD_CMD_WRITE_ZEROES on server), Niels de Vos, 2016/07/20
- Re: [Qemu-devel] semantics of FIEMAP without FIEMAP_FLAG_SYNC (was Re: [PATCH v5 13/14] nbd: Implement NBD_CMD_WRITE_ZEROES on server), Dave Chinner, 2016/07/21
- Re: [Qemu-devel] semantics of FIEMAP without FIEMAP_FLAG_SYNC (was Re: [PATCH v5 13/14] nbd: Implement NBD_CMD_WRITE_ZEROES on server), Pádraig Brady, 2016/07/21
- Re: [Qemu-devel] semantics of FIEMAP without FIEMAP_FLAG_SYNC (was Re: [PATCH v5 13/14] nbd: Implement NBD_CMD_WRITE_ZEROES on server), Dave Chinner, 2016/07/21
- Re: [Qemu-devel] semantics of FIEMAP without FIEMAP_FLAG_SYNC (was Re: [PATCH v5 13/14] nbd: Implement NBD_CMD_WRITE_ZEROES on server), Paolo Bonzini, 2016/07/20
- Re: [Qemu-devel] semantics of FIEMAP without FIEMAP_FLAG_SYNC (was Re: [PATCH v5 13/14] nbd: Implement NBD_CMD_WRITE_ZEROES on server), Dave Chinner, 2016/07/21
- Re: [Qemu-devel] semantics of FIEMAP without FIEMAP_FLAG_SYNC (was Re: [PATCH v5 13/14] nbd: Implement NBD_CMD_WRITE_ZEROES on server), Pádraig Brady, 2016/07/21