On Sat, Apr 20, 2019 at 6:55 AM Christoph Hellwig <[email protected]> wrote: > > While we generally allow scatterlists to have offsets larger than page > size for an entry, and other subsystems like the crypto code make use of > that, the block layer isn't quite ready for that. Flip the switch back > to avoid them for now, and revisit that decision early in a merge window > once the known offenders are fixed. > > Fixes: 8a96a0e40810 ("block: rewrite blk_bvec_map_sg to avoid a nth_page > call") > Reported-by: Guenter Roeck <[email protected]> > Signed-off-by: Christoph Hellwig <[email protected]> > --- > block/blk-merge.c | 14 +++++++++++++- > 1 file changed, 13 insertions(+), 1 deletion(-) > > diff --git a/block/blk-merge.c b/block/blk-merge.c > index 247b17f2a0f6..21e87a714a73 100644 > --- a/block/blk-merge.c > +++ b/block/blk-merge.c > @@ -474,9 +474,21 @@ static unsigned blk_bvec_map_sg(struct request_queue *q, > while (nbytes > 0) { > unsigned offset = bvec->bv_offset + total; > unsigned len = min(get_max_segment_size(q, offset), nbytes); > + struct page *page = bvec->bv_page; > + > + /* > + * Unfortunately a fair number of drivers barf on scatterlists > + * that have an offset larger than PAGE_SIZE, despite other > + * subsystems dealing with that invariant just fine. For now > + * stick to the legacy format where we never present those > from > + * the block layer, but the code below should be removed once > + * these offenders (mostly MMC/SD drivers) are fixed. > + */ > + page += (offset >> PAGE_SHIFT); > + offset &= ~PAGE_MASK; > > *sg = blk_next_sg(sg, sglist); > - sg_set_page(*sg, bvec->bv_page, len, offset); > + sg_set_page(*sg, page, len, offset);
Reviewed-by: Ming Lei <[email protected]> -- Ming Lei
