Hi Al, >>>> it seems that efivarfs only supports readv(), but when it comes to >>>> writev(), I am getting an error. Is there any reason to not support >>>> vectored write on this filesystem? Especially with the uint32 header >>>> for each file, I think it would make perfect sense to support it. >>> >>> What error are you seeing? I thought that the vfs fell back to a looped >>> write if the file system doesn't support .write_iter()? >> >> that seems to work for readv(), but not for writev(). >> >>> But yes, we definitely should support writev(). >> >> I just get an EIO error and have not traced this down any further. > > What arguments are you feeding to it? Note that the thing is sensitive to > range boundaries; it's not as if series of write() to it would be equivalent > to single write() from concatenation. And writev() is equivalent to > series of write(). I did something really simple and from my point obvious. I took the uint32 header that every file needs and put that in iov[0] pointer and then the rest in iov[1] pointer. The reason was that I didn't want to copy the actual file content around to just add a uint32 header in front of it. > If you want behaviour a-la UDP sockets (syscall boundaries matter, > boundaries between vector elements do not), we can certainly do that, > but this is different from the current semantics. AFAICS, said > semantics makes little sense, but it's a user-visible change... I do not know about the specific semantics of efivarfs and frankly I have not tried every single combination. However it sounds to me that currently it requires that the whole file content is provided with a single write(). I have no idea if this is true or not. I do not know enough about the internals here. Maybe efivarfs just needs to implemented .write_iter properly to actually support writev() and can not rely on a fallback of multiple write() calls. Regards Marcel -- To unsubscribe from this list: send the line "unsubscribe linux-efi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
