On Fri, Feb 10, 2023 at 03:06:26PM +1100, Dave Chinner wrote: > So while I was pondering the complexity of this and watching a great > big shiny rocket create lots of heat, light and noise, it occurred That was kind of fun > to me that we already have a mechanism for preventing page cache > data from being changed while the folios are under IO: > SB_I_STABLE_WRITES and folio_wait_stable(). I thought about bringing that up, but it's not quite right. That works great for writeback, but it only works for writeback. We'd need to track another per-folio counter ... it'd be like the page pinning kerfuffle, only worse. And for such a rare thing it seems like a poor use of 32 bits of per-page state. Not to mention that you can effectively block all writes to a file for an indefinite time by splicing pages to a pipe that you then never read from.
