On Tue, Jul 26, 2016 at 11:51:25AM +0200, Stefan Bader wrote: > On 21.07.2016 10:58, Stefan Bader wrote: > > I was pointed at the thread which seems to address the same after > > I wrote most of below text. Did not want to re-write this so please > > bear with the odd layout. > > > > https://www.redhat.com/archives/dm-devel/2016-June/msg00015.html > > > > Zhengyuan tries to fix the problem by relocating the superblock on > > disk. But I am not sure whether there is really any guarantee about > > how __bread fills data into the buffer_head. What if there is the next > > odd arch with 128K pages? > > > > So below is an attempt to be more generic. Still I don't feel completely > > happy with the way that a page moves (or is shared) between buffer_head > > and biovec. What I tried to outline below is to let the register functions > > allocate bio+biovec memory and use the in-memory sb_cache data to initialize > > the biovec buffer. > > Any opinions here? Also adding LKML as I don't seem to get through moderation on > dm-devel. The correct solution is to rip out the __bread() and just read the superblock by issuing a bio, the same way all the other IO in bcache is done. This is the way it's done in the bcache-dev branch - unfortunately, the patch that does that in bcache-dev is big and invasive and probably not worth the hassle to backport: https://evilpiepirate.org/git/linux-bcache.git/commit/?h=bcache-dev&id=303eb67bffad57b4d9e71523e7df04bf258e66d1 Probably best to just do something small and localized. -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
