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nbd: Allow unmap and fua during write zeroes

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Commit fa778fff wired up support to send the NBD_CMD_WRITE_ZEROES,
but forgot to inform the block layer that FUA unmapping of zeroes is
supported.  Without BDRV_REQ_MAY_UNMAP listed as a supported flag,
the block layer will always insist on the NBD layer passing
NBD_CMD_FLAG_NO_HOLE, resulting in the server always allocating
things even when it was desired to let the server punch holes.
Similarly, failing to set BDRV_REQ_FUA means that the client may
send unnecessary NBD_CMD_FLUSH when it could have instead used the
NBD_CMD_FLAG_FUA bit.

CC: qemu-stable@nongnu.org
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <1479413642-22463-2-git-send-email-eblake@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Eric Blake 2016-11-17 14:13:54 -06:00 committed by Paolo Bonzini
parent c2a8531690
commit 169407e1f7
1 changed files with 4 additions and 0 deletions
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4
block/nbd-client.c
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@ -415,6 +415,10 @@ int nbd_client_init(BlockDriverState *bs,
}
if (client->nbdflags & NBD_FLAG_SEND_FUA) {
bs->supported_write_flags = BDRV_REQ_FUA;
bs->supported_zero_flags |= BDRV_REQ_FUA;
}
if (client->nbdflags & NBD_FLAG_SEND_WRITE_ZEROES) {
bs->supported_zero_flags |= BDRV_REQ_MAY_UNMAP;
}
qemu_co_mutex_init(&client->send_mutex);