From f9f76879bc4521019697970bad3bc1dd0bec211f Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Fri, 19 Apr 2019 08:56:24 +0200 Subject: block: avoid scatterlist offsets > PAGE_SIZE 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") Reviewed-by: Ming Lei Tested-by: Guenter Roeck Reported-by: Guenter Roeck Signed-off-by: Christoph Hellwig Signed-off-by: Jens Axboe --- block/blk-merge.c | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-) (limited to 'block/blk-merge.c') 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); total += len; nbytes -= len; -- cgit v1.2.3-70-g09d2