On Mon 08-10-18 20:58:23, Ernesto A. Fernández wrote:
> On a DIO_SKIP_HOLES filesystem, the ->get_block() method is currently
> not allowed to create blocks for an empty inode. This confusion comes
> from trying to bit shift a negative number, so check the size of the
> inode first.
>
> The problem is most visible for hfsplus, because the fallback to
> buffered I/O doesn't happen and the write fails with EIO. This is in
> part the fault of the module, because it gives a wrong return value on
> ->get_block(); that will be fixed in a separate patch.
>
> Signed-off-by: Ernesto A. Fernández <ernesto.mnd.fernandez@xxxxxxxxx>
Good catch. The patch looks good. You can add:
Reviewed-by: Jan Kara <jack@xxxxxxx>
Also Jens often picks up patches for direct IO code so added him to CC.
Jens?
Honza
> ---
> fs/direct-io.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/fs/direct-io.c b/fs/direct-io.c
> index 093fb54cd316..9a7b91a3b7a7 100644
> --- a/fs/direct-io.c
> +++ b/fs/direct-io.c
> @@ -679,6 +679,7 @@ static int get_more_blocks(struct dio *dio, struct dio_submit *sdio,
> unsigned long fs_count; /* Number of filesystem-sized blocks */
> int create;
> unsigned int i_blkbits = sdio->blkbits + sdio->blkfactor;
> + loff_t i_size;
>
> /*
> * If there was a memory error and we've overwritten all the
> @@ -708,8 +709,8 @@ static int get_more_blocks(struct dio *dio, struct dio_submit *sdio,
> */
> create = dio->op == REQ_OP_WRITE;
> if (dio->flags & DIO_SKIP_HOLES) {
> - if (fs_startblk <= ((i_size_read(dio->inode) - 1) >>
> - i_blkbits))
> + i_size = i_size_read(dio->inode);
> + if (i_size && fs_startblk <= (i_size - 1) >> i_blkbits)
> create = 0;
> }
>
> --
> 2.11.0
>
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR
