Re: [PATCH] introduce XLogLockBlockRangeForCleanup()

I think we should say this though

LockBufHdr(buf);

valid = ((buf->flags & BM_VALID) != 0);

if (valid)
    PinBuffer_Locked(buf);
else
    UnlockBufHdr(buf);

since otherwise we would access the buffer flags without the spinlock
and we would leak a pin if the buffer was not valid