On Wed, Sep 23 2009 at 8:07pm -0400, Mike Snitzer <snitzer@xxxxxxxxxx> wrote: > Mikulas, > > I can easily reproduce the BUG you reported (you were running on > sparc64) if I take the following patch out of the quilt series: > http://people.redhat.com/msnitzer/patches/snapshot-merge/kernel_unified/2.6.31/dm-exstore-persistent-allow-metadata-reread.patch > > I've made an adjusted quilt series available here: > http://people.redhat.com/msnitzer/patches/snapshot-merge/kernel_unified_no_reread/2.6.31/ > > I'll be working to sort this out but I wanted to give you a heads up > that I can now easily reproduce the BUG on x86. Don't even need to stop > the merge and restart; just a normal merge triggers the BUG after the > first extent of chunks is merged. Turns out the BUG doesn't occur immediately after processing the first extent of chunks (via merge_callback). It occurs IFF the chunks are _not_ processed in descending order, e.g.: ... start merge chunk=29939 linear_chunks=160 finish merge chunk=29939 finish merge chunk=29938 finish merge chunk=29937 finish merge chunk=29936 ... finish merge chunk=29784 finish merge chunk=29783 finish merge chunk=29782 finish merge chunk=29781 finish merge chunk=29780 start merge chunk=29736 linear_chunks=3 finish merge chunk=29736 finish merge chunk=29735 finish merge chunk=29734 start merge chunk=29779 linear_chunks=43 finish merge chunk=29779 ------------[ cut here ]------------ kernel BUG at drivers/md/dm-snap-persistent.c:456! ... So in the above you see chunks 29734-29736 gets interleaved between 29779 and 29780. This provided the hint I needed to fix the fact that when we moved dm-snapshot-dont-insert-before-existing-chunk.patch to the beginning of the series we neglected to adjust dm-snapshot-move-exception-code-to-new-file.patch accordingly. As a result dm-snapshot-move-exception-code-to-new-file.patch had reintroduced inserting the exceptions into the hash_table before other exceptions.. Mikulas/Jon, I'd really appreciate it if you could test the following updated quilt tree(s): http://people.redhat.com/msnitzer/patches/snapshot-merge/kernel_unified/2.6.31/ http://people.redhat.com/msnitzer/patches/snapshot-merge/kernel_unified_no_reread/2.6.31/ Mikulas, the 'kernel_unified_no_reread' quilt tree is slightly more minimalist (avoids adding re-read support to dm-snap-persistent.c) so it is worth a shot if 'kernel_unified' still fails for you. Both work for me on x86_64. But we may not be out of the woods on sparc64. Thanks, Mike -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
