On Fri, Apr 18, 2025 at 04:52:46PM -0500, Eric Blake wrote: > This patch is purely mechanical, changing bool want_zero into an > unsigned int for bitwise-or of flags. As of this patch, all > implementations are unchanged (the old want_zero==true is now > mode==BDRV_WANT_PRECISE which is a superset of BDRV_WANT_ZERO); but > the callers in io.c that used to pass want_zero==false are now > prepared for future driver changes that can now distinguish bewteen > BDRV_WANT_ZERO vs. BDRV_WANT_ALLOCATED. The next patch will actually > change the file-posix driver along those lines, now that we have > more-specific hints. > > As for the background why this patch is useful: right now, the > file-posix driver recognizes that if allocation is being queried, the > entire image can be reported as allocated (there is no backing file to > refer to) - but this throws away information on whether the entire > image reads as zero (trivially true if lseek(SEEK_HOLE) at offset 0 > returns -ENXIO, a bit more complicated to prove if the raw file was > created with 'qemu-img create' since we intentionally allocate a small > chunk of all-zero data to help with alignment probing). Later patches > will add a generic algorithm for seeing if an entire file reads as > zeroes. > > Signed-off-by: Eric Blake <ebl...@redhat.com> > --- > > In response to Stefan's ask for what it would look like as a bitmask > of flags instead of an enum. Only the first two patches of the series > change. > > block/coroutines.h | 4 +-- > include/block/block-common.h | 11 +++++++ > include/block/block_int-common.h | 27 +++++++++-------- > include/block/block_int-io.h | 4 +-- > block/io.c | 51 ++++++++++++++++---------------- > block/blkdebug.c | 6 ++-- > block/copy-before-write.c | 4 +-- > block/file-posix.c | 4 +-- > block/gluster.c | 4 +-- > block/iscsi.c | 6 ++-- > block/nbd.c | 4 +-- > block/null.c | 6 ++-- > block/parallels.c | 6 ++-- > block/qcow.c | 2 +- > block/qcow2.c | 6 ++-- > block/qed.c | 6 ++-- > block/quorum.c | 4 +-- > block/raw-format.c | 4 +-- > block/rbd.c | 6 ++-- > block/snapshot-access.c | 4 +-- > block/vdi.c | 4 +-- > block/vmdk.c | 2 +- > block/vpc.c | 2 +- > block/vvfat.c | 6 ++-- > tests/unit/test-block-iothread.c | 2 +- > 25 files changed, 99 insertions(+), 86 deletions(-)
Reviewed-by: Stefan Hajnoczi <stefa...@redhat.com>
signature.asc
Description: PGP signature
