> On Feb 20, 2019, at 6:44 AM, Matthew Wilcox <willy@xxxxxxxxxxxxx> wrote: > > That interface would need to have some hint from the VFS as to what > range of file offsets it's looking for, and which page is the critical > one. Maybe that's as simple as passing in pgoff and order, where pgoff is > not necessarily aligned to 1<<order. Or maybe we want to explicitly > pass in start, end, critical. The order is especially important, as I think it's vital that the FS can tell the difference between a caller wanting 2M in PAGESIZE pages (something that could be satisfied by taking multiple trips through the existing readahead) or needing to transfer ALL the content for a 2M page as the fault can't be satisfied until the operation is complete. It also won't be long before reading 1G at a time to map PUD-sized pages becomes more important, plus the need to support various sizes in-between for architectures like ARM that support them (see the non-standard size THP discussion for more on that.) I'm also hoping the conference would have enough "mixer" time that MM folks can have a nice discussion with the FS folks to get their input - or at the very least these mail threads will get that ball rolling.
