On 4/13/2015 5:21 PM, Akinobu Mita wrote:
When CONFIG_DEBUG_SG=y and DIF protection support enabled, kernel BUG()s are triggered due to the following two issues: 1) prot_sg is not initialized by sg_init_table(). When CONFIG_DEBUG_SG=y, scatterlist helpers check sg entry has a correct magic value. 2) vmalloc'ed buffer is passed to sg_set_buf(). sg_set_buf() uses virt_to_page() to convert virtual address to struct page, but it doesn't work with vmalloc address. vmalloc_to_page() should be used instead. As prot_buf isn't usually too large, so fix it by allocating prot_buf by kmalloc instead of vmalloc.
Hi Akinobu, This obviously fixes a bug, but I'm afraid that for certain workloads (large IO size) this would trigger higher order allocations. how about removing the prot_buf altogether? The only reason why this bounce is used is to allow code sharing with rd_mcp DIF mode calling sbc_verify_[write|read]. But I'd say it doesn't make sense anymore given these fixes. IMO, the t_prot_sg can be used just like t_data_sg. In the read case, we just read the data into t_prot_sg using bvec_iter (better to reuse fd_do_rw code) and just call __sbc_dif_verify_read (that would not copy sg's). In the write case, we call sbc_dif_verify_write() with NULL to avoid the copy and then just write it to the file (reusing fd_do_rw code). Thoughts? Sagi. -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
