Re: [Libguestfs] [libnbd PATCH] api: Speed up nbd_pread_structured when reading holes

On Fri, May 27, 2022 at 05:25:43PM -0500, Eric Blake wrote: > Commit c7fbc71d missed an optimization: when we guarantee that a pread > buffer is pre-zeroed, we don't need to waste time memset()ing it when > the server sends a hole. But the next commit e0953cb7 lets the user > skip pre-zeroing, at which point the memset is required to avoid data > corruption. Thankfully, we are not leaking bogus bytes when a server > sends a hole, but we CAN speed up the case where we have pre-zeroed > the buffer to avoid a second memset(). Because the user can change > the state of pread_initialize on the fly (including while a pread is > still in flight), we must track the state per-command as it was before > we send the request to the server. > ---

Reviewed-by: Richard W.M. Jones <rjones(a)redhat.com&gt;