Control: fixed -1 1:2.10.0-1 05.12.2019 18:35, Michael Tokarev wrote:
Control: fixed -1 1:3.1+dfsg-8+deb10u3
Actually this is fixed by this commit: commit c61e684e44272f2acb2bef34cf2aa234582a73a9 Author: Eric Blake <ebl...@redhat.com> Date: Thu May 4 21:15:00 2017 -0500 block: Exploit BDRV_BLOCK_EOF for larger zero blocks When we have a BDS with unallocated clusters, but asking the status of its underlying bs->file or backing layer encounters an end-of-file condition, we know that the rest of the unallocated area will read as zeroes. However, pre-patch, this required two separate calls to bdrv_get_block_status(), as the first call stops at the point where the underlying file ends. Thanks to BDRV_BLOCK_EOF, we can now widen the results of the primary status if the secondary status already includes BDRV_BLOCK_ZERO. In turn, this fixes a TODO mentioned in iotest 154, where we can now see that all sectors in a partial cluster at the end of a file read as zero when coupling the shorter backing file's status along with our knowledge that the remaining sectors came from an unallocated cluster. Also, note that the loop in bdrv_co_get_block_status_above() had an inefficent exit: in cases where the active layer sets BDRV_BLOCK_ZERO but does NOT set BDRV_BLOCK_ALLOCATED (namely, where we know we read zeroes merely because our unallocated clusters lie beyond the backing file's shorter length), we still ended up probing the backing layer even though we already had a good answer. Which went into qemu 2.10. However, backporting it to 2.8 requires a bit more of background, i/o subsystem has been modified significantly between 2.8 and 2.10. Thanks, /mjt