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nbd: Use BDRV_REQ_FUA for better FUA where supported 

Rather than always flushing ourselves, let the block layer
forward the FUA on to the underlying device - where all
underlying layers also understand FUA, we are now more
efficient; and where any underlying layer doesn't understand
it, now the block layer takes care of the full flush fallback
on our behalf.

Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <1463006384-7734-2-git-send-email-eblake@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Eric Blake 2016-05-11 16:39:34 -06:00 committed by Paolo Bonzini
parent 37146e7eaf
commit a0c303693e
1 changed files with 6 additions and 10 deletions
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16
nbd/server.c
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@ -1038,6 +1038,7 @@ static void nbd_trip(void *opaque)
struct nbd_reply reply;
ssize_t ret;
uint32_t command;
int flags;
TRACE("Reading request.");
if (client->closing) {
@ -1114,23 +1115,18 @@ static void nbd_trip(void *opaque)
TRACE("Writing to device");
flags = 0;
if (request.type & NBD_CMD_FLAG_FUA) {
flags |= BDRV_REQ_FUA;
}
ret = blk_pwrite(exp->blk, request.from + exp->dev_offset,
req->data, request.len, 0);
req->data, request.len, flags);
if (ret < 0) {
LOG("writing to file failed");
reply.error = -ret;
goto error_reply;
}
if (request.type & NBD_CMD_FLAG_FUA) {
ret = blk_co_flush(exp->blk);
if (ret < 0) {
LOG("flush failed");
reply.error = -ret;
goto error_reply;
}
}
if (nbd_co_send_reply(req, &reply, 0) < 0) {
goto out;
}