On Mon 15-08-16 13:09:12, Ross Zwisler wrote:
> When DAX calls ext2_get_block() and the file offset points to a hole we
> currently don't set bh_result->b_size. When we re-enable PMD faults DAX
> will need bh_result->b_size to tell it the size of the hole so it can
> decide whether to fault in a 4 KiB zero page or a 2 MiB zero page.
>
> For ext2 we always want DAX to use 4 KiB zero pages, so we just tell DAX
> that all holes are 4 KiB in size.
>
> Signed-off-by: Ross Zwisler <ross.zwisler@xxxxxxxxxxxxxxx>
> ---
> fs/ext2/inode.c | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> diff --git a/fs/ext2/inode.c b/fs/ext2/inode.c
> index d5c7d09..c6d9763 100644
> --- a/fs/ext2/inode.c
> +++ b/fs/ext2/inode.c
> @@ -773,6 +773,12 @@ int ext2_get_block(struct inode *inode, sector_t iblock, struct buffer_head *bh_
> if (ret > 0) {
> bh_result->b_size = (ret << inode->i_blkbits);
> ret = 0;
> + } else if (ret == 0 && IS_DAX(inode)) {
I'd just drop the IS_DAX() check and set
bh_result->b_size = 1 << inode->i_blkbits;
IMO it's better to have things consistent between DAX & !DAX whenever
possible.
Honza
> + /*
> + * We have hit a hole. Tell DAX it is 4k in size so that it
> + * uses PTE faults.
> + */
> + bh_result->b_size = PAGE_SIZE;
> }
> return ret;
>
> --
> 2.9.0
>
>
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR
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