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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: 8a96a0e408 ("block: rewrite blk_bvec_map_sg to avoid a nth_page call")
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Reported-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Christoph Hellwig 2019-04-19 08:56:24 +02:00 committed by Jens Axboe
parent f6b50160a0
commit f9f76879bc
1 changed files with 13 additions and 1 deletions
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14
block/blk-merge.c
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@ -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;