On Mon, Jul 02, 2018 at 02:50:36PM +0200, Christoph Hellwig wrote:
> The problem is that we need to split extents at the eof block
> so that the existing zeroing actually takes effect. The patch below
> fixes the test case for me:
>
Looks sane at a glance. I'll take a closer look at v7 and run some more
testing..
Brian
> diff --git a/fs/iomap.c b/fs/iomap.c
> index e8f1bcdc95cf..9c88b8736de0 100644
> --- a/fs/iomap.c
> +++ b/fs/iomap.c
> @@ -143,13 +143,20 @@ static void
> iomap_adjust_read_range(struct inode *inode, struct iomap_page *iop,
> loff_t *pos, loff_t length, unsigned *offp, unsigned *lenp)
> {
> + unsigned block_bits = inode->i_blkbits;
> + unsigned block_size = (1 << block_bits);
> unsigned poff = *pos & (PAGE_SIZE - 1);
> unsigned plen = min_t(loff_t, PAGE_SIZE - poff, length);
> + unsigned first = poff >> block_bits;
> + unsigned last = (poff + plen - 1) >> block_bits;
> + unsigned end = (i_size_read(inode) & (PAGE_SIZE - 1)) >> block_bits;
>
> + /*
> + * If the block size is smaller than the page size we need to check the
> + * per-block uptodate status and adjust the offset and length if needed
> + * to avoid reading in already uptodate ranges.
> + */
> if (iop) {
> - unsigned block_size = i_blocksize(inode);
> - unsigned first = poff >> inode->i_blkbits;
> - unsigned last = (poff + plen - 1) >> inode->i_blkbits;
> unsigned int i;
>
> /* move forward for each leading block marked uptodate */
> @@ -159,17 +166,27 @@ iomap_adjust_read_range(struct inode *inode, struct iomap_page *iop,
> *pos += block_size;
> poff += block_size;
> plen -= block_size;
> + first++;
> }
>
> /* truncate len if we find any trailing uptodate block(s) */
> for ( ; i <= last; i++) {
> if (test_bit(i, iop->uptodate)) {
> plen -= (last - i + 1) * block_size;
> + last = i - 1;
> break;
> }
> }
> }
>
> + /*
> + * If the extent spans the block that contains the i_size we need to
> + * handle both halves separately so that we properly zero data in the
> + * page cache for blocks that are entirely outside of i_size.
> + */
> + if (first <= end && last > end)
> + plen -= (last - end) * block_size;
> +
> *offp = poff;
> *lenp = plen;
> }
> --
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