From: Keith Busch <[email protected]> This addresses the misaligned direct-io problem behind various threads:
https://lore.kernel.org/linux-xfs/[email protected]/ https://lore.kernel.org/all/CAC_j7i1R7oy+nRhxEjCTba=dugn02w9x+p94dcu0ahv5+5t...@mail.gmail.com/ https://lore.kernel.org/linux-block/ai7rnH20IYeSmY8s@gallifrey/ https://lore.kernel.org/linux-block/[email protected]/ The previously tested fixes are correct as far as they go, but they treat the symptom: they only matter because an invalid bio reaches those drivers in the first place. The reason it reaches them is an assumption I made when I removed direct-io alignment checks in 5ff3f74e145a ("block: simplify direct io validity check") and 7eac331869575 ("iomap: simplify direct io validity check"): every bio is eventually split to the device limits, and the upper layers cope with resulting errors once the bio has formed. Both were optimistic assumptions. Drivers with their own ->submit_bio may never pass through blk_mq_submit_bio()'s split, so the check never runs for them, and as numerous threads showed, the consumers don't uniformly handle this condition. This series stops the invalid bio at the source instead. It validates the buffer's alignment against the alignment limits when the bio is built from the iov_iter. The check is folded into the bvec extraction that already walks the vectors, so it adds only a comparison on a path that is pinning direct-io pages anyway. Misalignment is now uniformly rejected with EINVAL before submission for every direct-io path. v2->v3: - Dropped the bio_endio_errno helper and open-coded its two users. - Documented the ITER_BVEC alignment expectation in uio.h and reworded the bvec check comment; the exhaustive per-segment validation stays behind CONFIG_DEBUG_KERNEL as a contract assertion. - Reworked zloop_get_block_size() to mirror loop's structure. - loop/zloop only ever tighten dma_alignment beyond the default. I think these could use more relaxed alignments, but I'm just being extra conservative against introducing new changes here. Previous version: https://lore.kernel.org/linux-block/[email protected]/ Keith Busch (5): block: use blkdev_iov_iter_get_pages status for errors block: fix dio leak on metadata mapping error loop: set dma_alignment from the backing file for direct I/O zloop: set dma_alignment from the backing files for direct I/O block: validate user space vectors during extraction block/bio.c | 56 ++++++++++++++++++++++++++++++++++++++++--- block/blk-map.c | 2 +- block/fops.c | 10 ++++---- drivers/block/loop.c | 46 ++++++++++++++++++++++++++++------- drivers/block/zloop.c | 35 +++++++++++++++++++-------- fs/iomap/direct-io.c | 1 + include/linux/bio.h | 2 +- include/linux/uio.h | 10 +++++++- lib/iov_iter.c | 9 ++++++- 9 files changed, 142 insertions(+), 29 deletions(-) base-commit: 5c7804e3279c9bdc36e5eac743b4000633b25f65 -- 2.53.0-Meta
