David Dillow <dillowda@xxxxxxxx> writes:
> When using devices that support max_segments > BIO_MAX_PAGES (256),
> direct IO tries to allocate a bio with more pages than allowed, which
> leads to an oops in dio_bio_alloc(). Clamp the request to the supported
> maximum, and change dio_bio_alloc() to reflect that bio_alloc() will
> always return a bio when called with __GFP_WAIT and a valid number of
> vectors.
I like this version better than the first, just clean up the comment to
conform to CodingStyle and you can add my
Reviewed-by: Jeff Moyer <jmoyer@xxxxxxxxxx>
Be sure to CC akpm on the next posting, as DIO changes usually go in
through his tree.
Cheers,
Jeff
> Signed-off-by: David Dillow <dillowda@xxxxxxxx>
> --
> Second alternate, my preferred that reflects that bio_alloc() cannot
> fail when properly called. I can take or leave the comment.
>
>
> diff --git a/fs/direct-io.c b/fs/direct-io.c
> index 85882f6..96a01d8 100644
> --- a/fs/direct-io.c
> +++ b/fs/direct-io.c
> @@ -325,13 +325,17 @@ void dio_end_io(struct bio *bio, int error)
> }
> EXPORT_SYMBOL_GPL(dio_end_io);
>
> -static int
> +static void
> dio_bio_alloc(struct dio *dio, struct block_device *bdev,
> sector_t first_sector, int nr_vecs)
> {
> struct bio *bio;
>
> + /* bio_alloc() is guaranteed to return a bio when called with
> + * __GFP_WAIT and we request a valid number of vectors.
> + */
> bio = bio_alloc(GFP_KERNEL, nr_vecs);
> + BUG_ON(!bio);
>
> bio->bi_bdev = bdev;
> bio->bi_sector = first_sector;
> @@ -342,7 +346,6 @@ dio_bio_alloc(struct dio *dio, struct block_device *bdev,
>
> dio->bio = bio;
> dio->logical_offset_in_bio = dio->cur_page_fs_offset;
> - return 0;
> }
>
> /*
> @@ -583,8 +586,9 @@ static int dio_new_bio(struct dio *dio, sector_t start_sector)
> goto out;
> sector = start_sector << (dio->blkbits - 9);
> nr_pages = min(dio->pages_in_io, bio_get_nr_vecs(dio->map_bh.b_bdev));
> + nr_pages = min(nr_pages, BIO_MAX_PAGES);
> BUG_ON(nr_pages <= 0);
> - ret = dio_bio_alloc(dio, dio->map_bh.b_bdev, sector, nr_pages);
> + dio_bio_alloc(dio, dio->map_bh.b_bdev, sector, nr_pages);
> dio->boundary = 0;
> out:
> return ret;
--
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