block: use pwrite_zeroes_alignment when writing first sector

Since commit 5634622bcb ("file-posix: allow BLKZEROOUT with -t
writeback"), qemu-img create errors out on a Linux loop block device
with a 4 KB sector size:

  # dd if=/dev/zero of=blockfile bs=1M count=1024
  # losetup --sector-size 4096 /dev/loop0 blockfile
  # qemu-img create -f raw /dev/loop0 1G
  Formatting '/dev/loop0', fmt=raw size=1073741824
  qemu-img: /dev/loop0: Failed to clear the new image's first sector: Invalid argument

Use the pwrite_zeroes_alignment block limit to avoid misaligned
fallocate(2) or ioctl(BLKZEROOUT) in the block/file-posix.c block
driver.

Cc: qemu-stable@nongnu.org
Fixes: 5634622bcb ("file-posix: allow BLKZEROOUT with -t writeback")
Reported-by: Jean-Louis Dupond <jean-louis@dupond.be>
Buglink: https://gitlab.com/qemu-project/qemu/-/issues/3127
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-ID: <20251007141700.71891-3-stefanha@redhat.com>
Tested-by: Fiona Ebner <f.ebner@proxmox.com>
Reviewed-by: Fiona Ebner <f.ebner@proxmox.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Stefan Hajnoczi
2025-10-07 10:16:59 -04:00
committed by Kevin Wolf
parent 98e788b91a
commit d704a13d2c
3 changed files with 14 additions and 1 deletions
+1
View File
@@ -116,6 +116,7 @@ BlockAIOCB *blk_abort_aio_request(BlockBackend *blk,
void *opaque, int ret);
uint32_t blk_get_request_alignment(BlockBackend *blk);
uint32_t blk_get_pwrite_zeroes_alignment(BlockBackend *blk);
uint32_t blk_get_max_transfer(BlockBackend *blk);
uint64_t blk_get_max_hw_transfer(BlockBackend *blk);