Hi, On Thu 11-10-12 10:46:29, Clement Gallin-Douathe wrote: > I am working on ARMv7 dual-core board with android (ICS + kernel 3.4.9). > I am randomly facing a kernel oops in fs/jbd2/journal.c: In the > function jbd2_journal_get_descriptor_buffer, memset is called > without checking bh->b_data which is NULL in my case. > > It seems to be a problem with the journal device block. > It seems that the current memory zone is high memory zone, so the > current buffer head referred to the used page is not correctly set > (b_data is NULL). > > I could not find why the buffer cache tries to allocate and use a > block in high memory zone. > Any ideas, or tips/tricks for debugging ? Well, the question is how a highmem page got to jbd2_journal_get_descriptor_buffer(). In fs/block_dev.c:bdget() we do mapping_set_gfp_mask(&inode->i_data, GFP_USER) where GFP_USER is (__GFP_WAIT | __GFP_IO | __GFP_FS | __GFP_HARDWALL). That means !__GFP_HIGH in particular. So does the device ext4 is mounted on play some tricks with mapping flags? If not, I'd instrument grow_dev_page() in fs/buffer.c to check whether the returned page is not highmem... If yes, look further into the allocator. If no, it could be a bug in page migration code from mm/migrate.c. Honza -- Jan Kara <jack@xxxxxxx> SUSE Labs, CR -- 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
