Re: [PATCH 11/19] block: implement bio helper to add iter bvec pages to bio

[Jens Axboe <axboe@kernel.dk>]

On 2/20/19 3:58 PM, Ming Lei wrote:
> On Mon, Feb 11, 2019 at 12:00:41PM -0700, Jens Axboe wrote:
>> For an ITER_BVEC, we can just iterate the iov and add the pages
>> to the bio directly. This requires that the caller doesn't releases
>> the pages on IO completion, we add a BIO_NO_PAGE_REF flag for that.
>>
>> The current two callers of bio_iov_iter_get_pages() are updated to
>> check if they need to release pages on completion. This makes them
>> work with bvecs that contain kernel mapped pages already.
>>
>> Reviewed-by: Hannes Reinecke <hare@suse.com>
>> Reviewed-by: Christoph Hellwig <hch@lst.de>
>> Signed-off-by: Jens Axboe <axboe@kernel.dk>
>> ---
>>  block/bio.c               | 59 ++++++++++++++++++++++++++++++++-------
>>  fs/block_dev.c            |  5 ++--
>>  fs/iomap.c                |  5 ++--
>>  include/linux/blk_types.h |  1 +
>>  4 files changed, 56 insertions(+), 14 deletions(-)
>>
>> diff --git a/block/bio.c b/block/bio.c
>> index 4db1008309ed..330df572cfb8 100644
>> --- a/block/bio.c
>> +++ b/block/bio.c
>> @@ -828,6 +828,23 @@ int bio_add_page(struct bio *bio, struct page *page,
>>  }
>>  EXPORT_SYMBOL(bio_add_page);
>>  
>> +static int __bio_iov_bvec_add_pages(struct bio *bio, struct iov_iter *iter)
>> +{
>> +	const struct bio_vec *bv = iter->bvec;
>> +	unsigned int len;
>> +	size_t size;
>> +
>> +	len = min_t(size_t, bv->bv_len, iter->count);
>> +	size = bio_add_page(bio, bv->bv_page, len,
>> +				bv->bv_offset + iter->iov_offset);
> 
> iter->iov_offset needs to be subtracted from 'len', looks
> the following delta change[1] is required, otherwise memory corruption
> can be observed when running xfstests over loop/dio.

Thanks, I folded this in.

-- 
Jens Axboe