| Message ID | 1460717488-19796-1-git-send-email-ming.lei@canonical.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
-------- Forwarded Message -------- Subject: Re: [PATCH] block: loop: fix filesystem corruption in case of aio/dio Date: Fri, 15 Apr 2016 21:16:42 +0800 From: Ming Lei <ming.lei@canonical.com> To: Holger Hoffstätte <holger.hoffstaette@googlemail.com> On Fri, Apr 15, 2016 at 8:51 PM, Holger Hoffstätte <holger.hoffstaette@googlemail.com> wrote: > (off-list since I'm likely missing something..) > > Hello Ming Lei, > > quick question - > > On 04/15/16 12:51, Ming Lei wrote: >> Starting from commit e36f620428(block: split bios to max possible length), >> block core starts to split bio in the middle of bvec. >> >> Unfortunately loop dio/aio doesn't consider this situation, and >> always treat 'iter.iov_offset' as zero. Then filesystem corruption >> is observed. >> >> This patch figures out the offset of the base bvevc via >> 'bio->bi_iter.bi_bvec_done' and fixes the issue by passing the offset >> to iov iterator. >> >> Fixes: e36f6204288088f (block: split bios to max possible length) >> Cc: Keith Busch <keith.busch@intel.com> >> Cc: Al Viro <viro@zeniv.linux.org.uk> >> Cc: stable@vger.kernel.org (4.5) > ^^^^^ > > The previous patch went into 4.4.x-stable, so should this one not go > into 4.4.x as well? It applies cleanly and does not seem to hurt. > Apologies in advance if this is a bad idea. :) You are absolutely right, this patch should have been marked as stable 4.4+, thanks for point it out! Jens, please let me know if you need me to resend the patch for fixing the stable tag. Thanks, Ming -- To unsubscribe from this list: send the line "unsubscribe linux-block" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 04/15/2016 04:51 AM, Ming Lei wrote: > Starting from commit e36f620428(block: split bios to max possible length), > block core starts to split bio in the middle of bvec. > > Unfortunately loop dio/aio doesn't consider this situation, and > always treat 'iter.iov_offset' as zero. Then filesystem corruption > is observed. > > This patch figures out the offset of the base bvevc via > 'bio->bi_iter.bi_bvec_done' and fixes the issue by passing the offset > to iov iterator. > > Fixes: e36f6204288088f (block: split bios to max possible length) > Cc: Keith Busch <keith.busch@intel.com> > Cc: Al Viro <viro@zeniv.linux.org.uk> > Cc: stable@vger.kernel.org (4.5) > Signed-off-by: Ming Lei <ming.lei@canonical.com> Thanks Ming, queued up.
diff --git a/drivers/block/loop.c b/drivers/block/loop.c index 7e5e27a..1fa8cc2 100644 --- a/drivers/block/loop.c +++ b/drivers/block/loop.c @@ -488,6 +488,12 @@ static int lo_rw_aio(struct loop_device *lo, struct loop_cmd *cmd, bvec = __bvec_iter_bvec(bio->bi_io_vec, bio->bi_iter); iov_iter_bvec(&iter, ITER_BVEC | rw, bvec, bio_segments(bio), blk_rq_bytes(cmd->rq)); + /* + * This bio may be started from the middle of the 'bvec' + * because of bio splitting, so offset from the bvec must + * be passed to iov iterator + */ + iter.iov_offset = bio->bi_iter.bi_bvec_done; cmd->iocb.ki_pos = pos; cmd->iocb.ki_filp = file;
Starting from commit e36f620428(block: split bios to max possible length), block core starts to split bio in the middle of bvec. Unfortunately loop dio/aio doesn't consider this situation, and always treat 'iter.iov_offset' as zero. Then filesystem corruption is observed. This patch figures out the offset of the base bvevc via 'bio->bi_iter.bi_bvec_done' and fixes the issue by passing the offset to iov iterator. Fixes: e36f6204288088f (block: split bios to max possible length) Cc: Keith Busch <keith.busch@intel.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: stable@vger.kernel.org (4.5) Signed-off-by: Ming Lei <ming.lei@canonical.com> --- drivers/block/loop.c | 6 ++++++ 1 file changed, 6 insertions(+)