On 9/17/21 8:49 AM, Al Viro wrote: > On Fri, Sep 17, 2021 at 08:44:32AM -0600, Jens Axboe wrote: >> Hi Linus, >> >> This adds a helper to save/restore iov_iter state, and modifies io_uring >> to use it. After that is done, we can kill the iter->truncated addition >> that we added for this release. The io_uring change is being overly >> cautious with the save/restore/advance, but better safe than sorry and >> we can always improve that and reduce the overhead if it proves to be of >> concern. The only case to be worried about in this regard is huge IO, >> where iteration can take a while to iterate segments. >> >> I spent some time writing test cases, and expanded the coverage quite a >> bit from the last posting of this. liburing carries this regression test >> case now: >> >> https://git.kernel.dk/cgit/liburing/tree/test/file-verify.c >> >> which exercises all of this. It now also supports provided buffers, and >> explicitly tests for end-of-file/device truncation as well. >> >> On top of that, Pavel sanitized the IOPOLL retry path to follow the >> exact same pattern as normal IO. > > I can live with that; I do have problems with io-uring and its interactions > with iov_iter, but those are mostly independent from the stuff you are > doing here. I actually think we can end up cleaning up some of those bits post this, it'll definitely make it easier by having clean save/restore states. -- Jens Axboe
