On Nov 02, 2007 08:31 -0800, Badari Pulavarty wrote: > On Fri, 2007-11-02 at 13:20 +0800, Andreas Dilger wrote: > > On Nov 01, 2007 17:40 -0700, Mingming Cao wrote: > > > Current journal checksumming patch failed fsstress test on NUMA. The > > > bh->b_data passed to the crc32_be () function could be NULL pointer, > > > which caused kernel oops immediately when running fsstress with -o > > > journal_checksum. It is because the page is part of highmem on NUMA box. > > > We need to kmap the page before access the bh->b_data to calculate > > > the checksums. > > > > I have no objection to the patch, per-se, but I'm surprised that there > > would ever be a buffer head pointing at a page in high memory? That > > seems contrary to what I would expect... > > I was surprised to see that too while helping Mingming/Avantika track > this issue. I was under impression that we are checksumming only > metadata and it should be lowmem. But only "buffer_head"s are in lowmem. > Pages that point to can be in Highmem. But... this implies that every user of bh->b_data needs to kmap, and I don't see that in the code anywhere else. That makes me think something else is going wrong here. Cheers, Andreas -- Andreas Dilger Sr. Software Engineer, Lustre Group Sun Microsystems of Canada, Inc. - To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
