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Revision 97a2ae34

ID97a2ae34537882df34810d538ab1f51085499d2c

Added by Paolo Bonzini over 10 years ago

raw-posix: add support for write_zeroes on XFS and block devices

The code is similar to the implementation of discard and write_zeroes
with UNMAP. However, failure must be propagated up to block.c.

The stale page cache problem can be reproduced as follows:

  1. modprobe scsi-debug lbpws=1 lbprz=1
  2. ./qemu-io /dev/sdXX
    qemu-io> write -P 0xcc 0 2M
    qemu-io> write -z 0 1M
    qemu-io> read -P 0x00 0 512
    Pattern verification failed at offset 0, 512 bytes
    qemu-io> read -v 0 512
    00000000: cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc ................
    ...
  1. ./qemu-io --cache=none /dev/sdXX
    qemu-io> write -P 0xcc 0 2M
    qemu-io> write -z 0 1M
    qemu-io> read -P 0x00 0 512
    qemu-io> read -v 0 512
    00000000: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
    ...

And similarly with discard instead of "write -z".

Signed-off-by: Paolo Bonzini <>
Signed-off-by: Stefan Hajnoczi <>

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