If you could list the mistakes, the author could try making corrections and improve the text.
As regard O_DIRECT vs DMA, not sure what exactly you're saying. Understanding Linux Kernel book, for example, is using them quite interchangeably as well (4th edition, 2.6 kernel). Block devices are handled through interrupts and DMA, and these are lower-level means for doing IO. Scylla devs are using it quite interchangeably as well: https://github.com/scylladb/seastar/blob/master/core/reactor...
Wording might have been not optimal, but author never implied that O_DIRECT is DMA.
As regard O_DIRECT vs DMA, not sure what exactly you're saying. Understanding Linux Kernel book, for example, is using them quite interchangeably as well (4th edition, 2.6 kernel). Block devices are handled through interrupts and DMA, and these are lower-level means for doing IO. Scylla devs are using it quite interchangeably as well: https://github.com/scylladb/seastar/blob/master/core/reactor...
Wording might have been not optimal, but author never implied that O_DIRECT is DMA.
disclaimer: I'm the author.