Re: [patch] call truncate_inode_pages in the DIO fallback to buffered I/O path

[Zach Brown <zach.brown@oracle.com>]

> We have lots of nice new tools in-kernel which permit applications to
> manipulate and to invalidate pagecache.  Please, start using them rather
> than pushing bits of oracle into the core vfs ;)

And apps that were written before they were available? :)  We're OK with
their behaviour changing under newer kernels because they now have a
previous source of memory pressure that they didn't have before?

It seems a bit much to suggest that retaining the previous behaviour of
avoiding memory pressure by using the O_DIRECT API is somehow "pushing
bits of oracle into the core vfs" :).

Maybe that aspect of the API was unintentional, though.  That would be a
shame.  I suspect Oracle isn't alone in relying on it.

> Please, no truncate_inode_pages.  For this application, the far-safer
> invalidate_inode_pages() would suffice.

So now apps always have to pay the cost of looking up pages to
invalidate on the off chance that they wrote to a sparse region, based
on the current implementation detail that sparse regions fall back to
buffered?

- z