On 10/30/2017 09:01 AM, Nikolay Borisov wrote: > > > On 30.10.2017 15:55, David Sterba wrote: >> On Mon, Oct 30, 2017 at 03:21:51PM +0200, Nikolay Borisov wrote: >>> >>> >>> On 27.10.2017 07:17, Liu Bo wrote: >>>> On Tue, Oct 24, 2017 at 05:47:11AM -0500, Goldwyn Rodrigues wrote: >>>>> >>>>> EXTENT_PAGE_MAPPED gets set in set_page_extent_mapped(), but I don't see >>>>> it being cross checked anytime. What is the purpose of setting it? >>>> >>>> Please check commit d1310b2e0cd98eb1348553e69b73827b436dca7b, it was >>>> used to differentiate page for metadata and for data, but I think >>>> currently it's just a piece of legacy code. >>> >>> Be that as it may - is there any reason why we are keeping this and can >>> it be killed off? >> >> Are we're talking about EXTENT_PAGE_PRIVATE? There's no >> EXTENT_PAGE_MAPPED. There's some control dependency on the page private >> bit and the value, so we should be careful and replace the function with >> an assert (or a BUG_ON if it's a must-not-happen state). The page->private >> points to an extent buffer, and if it's always an eb, then the >> EXTENT_PAGE_PRIVATE is unused. > > I guess I meant do we actually need: set_page_extent_mapped and all the > jazz happening in it or is it a leftover (which I believe it is) ? >
We definitely need set_page_extent_mapped() to set the page private for the lowers layers to handle I/O, primarily writebacks. However, we may not need EXTENT_PAGE_PRIVATE (yes, I got it wrong the first time). I am still reading on this though. -- Goldwyn -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
