On 7.11.18 г. 8:31 ч., Dave Chinner wrote:
> From: Dave Chinner <dchinner@xxxxxxxxxx>
>
> iomap_dio_rw() has all the infrastructure in place to support block
> size > page size filesystems because it is essentially just
> sub-block DIO. It needs help, however, with the sub-block zeroing
> code (needs multi-page IOs) page cache invalidation over the block
> being written.
>
> Signed-off-by: Dave Chinner <dchinner@xxxxxxxxxx>
> ---
> fs/iomap.c | 65 ++++++++++++++++++++++++++++++++++++++++--------------
> 1 file changed, 49 insertions(+), 16 deletions(-)
>
> diff --git a/fs/iomap.c b/fs/iomap.c
> index 16d16596b00f..8878b1f1f9c7 100644
> --- a/fs/iomap.c
> +++ b/fs/iomap.c
> @@ -1548,21 +1548,34 @@ static void iomap_dio_bio_end_io(struct bio *bio)
> }
> }
>
> +/*
> + * With zeroing for block size larger than page size, the zeroing length can
> + * span multiple pages.
> + */
> +#define howmany(x, y) (((x)+((y)-1))/(y))
nit: This could be replaced by DIV_ROUND_UP
> static blk_qc_t
> iomap_dio_zero(struct iomap_dio *dio, struct iomap *iomap, loff_t pos,
> unsigned len)
> {
> struct page *page = ZERO_PAGE(0);
> struct bio *bio;
> + int npages = howmany(len, PAGE_SIZE);
> +
> + WARN_ON_ONCE(npages > 16);
>
> - bio = bio_alloc(GFP_KERNEL, 1);
> + bio = bio_alloc(GFP_KERNEL, npages);
> bio_set_dev(bio, iomap->bdev);
> bio->bi_iter.bi_sector = iomap_sector(iomap, pos);
> bio->bi_private = dio;
> bio->bi_end_io = iomap_dio_bio_end_io;
>
> - get_page(page);
> - __bio_add_page(bio, page, len, 0);
> + while (npages-- > 0) {
> + unsigned plen = min_t(unsigned, PAGE_SIZE, len);
> + get_page(page);
> + __bio_add_page(bio, page, plen, 0);
> + len -= plen;
> + }
> + WARN_ON(len != 0);
> bio_set_op_attrs(bio, REQ_OP_WRITE, REQ_SYNC | REQ_IDLE);
>
> atomic_inc(&dio->ref);
> @@ -1752,6 +1765,38 @@ iomap_dio_actor(struct inode *inode, loff_t pos, loff_t length,
> }
> }
>
> +/*
> + * This is lifted almost straight from xfs_flush_unmap_range(). Need a generic
> + * version of the block size rounding for these purposes.
> + */
> +static int
> +iomap_flush_unmap_range(struct file *f, loff_t offset, loff_t len)
> +{
> + struct inode *inode = file_inode(f);
> + loff_t rounding, start, end;
> + int ret;
> +
> + rounding = max_t(loff_t, i_blocksize(inode), PAGE_SIZE);
> + start = round_down(offset, rounding);
> + end = round_up(offset + len, rounding) - 1;
> +
> + ret = filemap_write_and_wait_range(inode->i_mapping, start, end);
> + if (ret)
> + return ret;
> +
> + /*
> + * Try to invalidate cache pages for the range we're direct
> + * writing. If this invalidation fails, tough, the write will
> + * still work, but racing two incompatible write paths is a
> + * pretty crazy thing to do, so we don't support it 100%.
> + */
> + ret = invalidate_inode_pages2_range(inode->i_mapping,
> + start >> PAGE_SHIFT, end >> PAGE_SHIFT);
> + if (ret)
> + dio_warn_stale_pagecache(f);
> + return 0;
> +}
> +
> /*
> * iomap_dio_rw() always completes O_[D]SYNC writes regardless of whether the IO
> * is being issued as AIO or not. This allows us to optimise pure data writes
> @@ -1829,22 +1874,10 @@ iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
> flags |= IOMAP_NOWAIT;
> }
>
> - ret = filemap_write_and_wait_range(mapping, start, end);
> + ret = iomap_flush_unmap_range(iocb->ki_filp, start, end);
> if (ret)
> goto out_free_dio;
>
> - /*
> - * Try to invalidate cache pages for the range we're direct
> - * writing. If this invalidation fails, tough, the write will
> - * still work, but racing two incompatible write paths is a
> - * pretty crazy thing to do, so we don't support it 100%.
> - */
> - ret = invalidate_inode_pages2_range(mapping,
> - start >> PAGE_SHIFT, end >> PAGE_SHIFT);
> - if (ret)
> - dio_warn_stale_pagecache(iocb->ki_filp);
> - ret = 0;
> -
> if (iov_iter_rw(iter) == WRITE && !dio->wait_for_completion &&
> !inode->i_sb->s_dio_done_wq) {
> ret = sb_init_dio_done_wq(inode->i_sb);
>
