Hello, I just had a look at the code checking delayed allocated buffers in ext4_ext_fiemap_cb(). I believe the checks there could use some elimiation of common patterns but that's just a minor thing. The main problem is that the code can easily crash the kernel when it races with page reclaim. You just cannot access most of the page contents (and for buffers it is especially true) without locking the page. Getting a reference via find_get_pages_tag() guarantees you the structure cannot go away but mm is still free to detach the page from the mapping at any moment. So you must always lock a page and check that it still belongs to the desired mapping before you check 'page_has_buffers()'. 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
