Messages in this thread | | | Date | Fri, 2 Aug 2013 19:40:15 +0400 | From | Maxim Patlasov <> | Subject | Re: [PATCH 10/16] fuse: Implement writepages callback |
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07/19/2013 08:50 PM, Miklos Szeredi пишет: > On Sat, Jun 29, 2013 at 09:45:29PM +0400, Maxim Patlasov wrote: >> From: Pavel Emelyanov <xemul@openvz.org> >> >> The .writepages one is required to make each writeback request carry more than >> one page on it. The patch enables optimized behaviour unconditionally, >> i.e. mmap-ed writes will benefit from the patch even if fc->writeback_cache=0. > I rewrote this a bit, so we won't have to do the thing in two passes, which > makes it simpler and more robust. Waiting for page writeback here is wrong > anyway, see comment above fuse_page_mkwrite(). BTW we had a race there because > fuse_page_mkwrite() didn't take the page lock. I've also fixed that up and > pushed a series containing these patches up to implementing ->writepages() to > > git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse.git writepages > > Passed some trivial testing but more is needed.
Thanks a lot for efforts. The approach you implemented looks promising, but it introduces the following assumption: a page cannot become dirty before we have a chance to wait on fuse writeback holding the page locked. This is already true for mmap-ed writes (due to your fixes) and it seems doable for cached writes as well (like we do in fuse_perform_write). But the assumption seems to be broken in case of direct read from local fs (e.g. ext4) to a memory region mmap-ed to a file on fuse fs. See how dio_bio_submit() marks pages dirty by bio_set_pages_dirty(). I can't see any solution for this use-case. Do you?
Thanks, Maxim
> > I'll get to the rest of the patches next week. > > Thanks, > Miklos > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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