qemu: improve efficiency of dd during snapshots
qemu: improve efficiency of dd during snapshots

POSIX states about dd:

If the bs=expr operand is specified and no conversions other than
sync, noerror, or notrunc are requested, the data returned from each
input block shall be written as a separate output block; if the read
returns less than a full block and the sync conversion is not
specified, the resulting output block shall be the same size as the
input block. If the bs=expr operand is not specified, or a conversion
other than sync, noerror, or notrunc is requested, the input shall be
processed and collected into full-sized output blocks until the end of
the input is reached.

Since we aren't using conv=sync, there is no zero-padding, but our
use of bs= means that a short read results in a short write.  If
instead we use ibs= and obs=, then short reads are collected and dd
only has to do a single write, which can make dd more efficient.

* src/qemu/qemu_monitor.c (qemuMonitorMigrateToFile):
Avoid 'dd bs=', since it can cause short writes.

warewolf/libvirt,andreabolognani/libvirt,andreabolognani/libvirt,datto/libvirt,siboulet/libvirt-openvz,shugaoye/libvirt,zhlcindy/libvirt-1.1.4-maintain,wiedi/libvirt,dumbbell/libvirt,wiedi/libvirt,jeckersb/libvirt,fabianfreyer/libvirt,rlaager/libvirt,siboulet/libvirt-openvz,VenkatDatta/libvirt,danwent/libvirt-ovs,eskultety/libvirt,crobinso/libvirt,novel/fbsd-libvirt,kantai/libvirt-vfork,fabianfreyer/libvirt,soulxu/libvirt-xuhj,fabianfreyer/libvirt,leilihh/libvirt,nertpinx/libvirt,rmarwaha/libvirt1,jardasgit/libvirt,dumbbell/libvirt,rlaager/libvirt,andreabolognani/libvirt,trainstack/libvirt,rlaager/libvirt,emaste/libvirt,novel/fbsd-libvirt,rmarwaha/libvirt1,cbosdo/libvirt,warewolf/libvirt,shugaoye/libvirt,jeckersb/libvirt,olafhering/libvirt,rmarwaha/libvirt,emaste/libvirt,eskultety/libvirt,zippy2/libvirt,trainstack/libvirt,leilihh/libvirt,rmarwaha/libvirt,novel/fbsd-libvirt,iam-TJ/libvirt,soulxu/libvirt-xuhj,rbu/libvirt,soulxu/libvirt-xuhj,wiedi/libvirt,wiedi/libvirt,datto/libvirt,emaste/libvirt,trainstack/libvirt,wiedi/libvirt,danwent/libvirt-ovs,novel/fbsd-libvirt,eskultety/libvirt,nertpinx/libvirt,dumbbell/libvirt,jeckersb/libvirt,emaste/libvirt,cbosdo/libvirt,iam-TJ/libvirt,trainstack/libvirt,bjzhang/libvirt,zippy2/libvirt,zippy2/libvirt,usc-isi/libvirt,libvirt/libvirt,leilihh/libvirt,iam-TJ/libvirt,usc-isi/libvirt,VenkatDatta/libvirt,rmarwaha/libvirt,dumbbell/libvirt,emaste/libvirt,foomango/libvirt,kantai/libvirt-vfork,iam-TJ/libvirt,rbu/libvirt,wiedi/libvirt,andreabolognani/libvirt,shugaoye/libvirt,bjzhang/libvirt,foomango/libvirt,soulxu/libvirt-xuhj,jardasgit/libvirt,usc-isi/libvirt,danwent/libvirt-ovs,zippy2/libvirt,foomango/libvirt,taget/libvirt,nertpinx/libvirt,taget/libvirt,andreabolognani/libvirt,rmarwaha/libvirt1,danwent/libvirt-ovs,usc-isi/libvirt,jfehlig/libvirt,jardasgit/libvirt,novel/fbsd-libvirt,crobinso/libvirt,olafhering/libvirt,cbosdo/libvirt,agx/libvirt,bjzhang/libvirt,rbu/libvirt,eskultety/libvirt,agx/libvirt,zhlcindy/libvirt-1.1.4-maintain,VenkatDatta/libvirt,nertpinx/libvirt,jeckersb/libvirt,zhlcindy/libvirt-1.1.4-maintain,eskultety/libvirt,soulxu/libvirt-xuhj,warewolf/libvirt,elmarco/libvirt,novel/fbsd-libvirt,trainstack/libvirt,iam-TJ/libvirt,agx/libvirt,emaste/libvirt,rbu/libvirt,olafhering/libvirt,VenkatDatta/libvirt,libvirt/libvirt,fabianfreyer/libvirt,leilihh/libvirt,jardasgit/libvirt,siboulet/libvirt-openvz,rmarwaha/libvirt1,novel/fbsd-libvirt,rlaager/libvirt,siboulet/libvirt-openvz,taget/libvirt,warewolf/libvirt,jeckersb/libvirt,rmarwaha/libvirt,kantai/libvirt-vfork,leilihh/libvirt,dumbbell/libvirt,elmarco/libvirt,shugaoye/libvirt,crobinso/libvirt,jeckersb/libvirt,elmarco/libvirt,zhlcindy/libvirt-1.1.4-maintain,agx/libvirt,rlaager/libvirt,agx/libvirt,wiedi/libvirt,jfehlig/libvirt,iam-TJ/libvirt,libvirt/libvirt,fabianfreyer/libvirt,rmarwaha/libvirt1,emaste/libvirt,crobinso/libvirt,datto/libvirt,leilihh/libvirt,siboulet/libvirt-openvz,zhlcindy/libvirt-1.1.4-maintain,bjzhang/libvirt,taget/libvirt,datto/libvirt,cbosdo/libvirt,novel/fbsd-libvirt,jardasgit/libvirt,elmarco/libvirt,elmarco/libvirt,cbosdo/libvirt,libvirt/libvirt,kantai/libvirt-vfork,iam-TJ/libvirt,shugaoye/libvirt,rmarwaha/libvirt1,foomango/libvirt,datto/libvirt,warewolf/libvirt,jeckersb/libvirt,taget/libvirt,kantai/libvirt-vfork,rmarwaha/libvirt,jfehlig/libvirt,danwent/libvirt-ovs,usc-isi/libvirt,jfehlig/libvirt,nertpinx/libvirt,warewolf/libvirt,novel/fbsd-libvirt,trainstack/libvirt,bjzhang/libvirt,dumbbell/libvirt,foomango/libvirt,rmarwaha/libvirt,VenkatDatta/libvirt,olafhering/libvirt,rbu/libvirt,warewolf/libvirt,trainstack/libvirt