On Fri, Jun 23, 2017 at 03:34:39PM +0200, Andreas Gruenbacher wrote:
> Filesystems can use this for implementing lseek SEEK_HOLE / SEEK_DATA
> support via iomap.
>
> Signed-off-by: Andreas Gruenbacher <[email protected]>
> ---
> fs/iomap.c | 89
> +++++++++++++++++++++++++++++++++++++++++++++++++++
> include/linux/iomap.h | 3 ++
> 2 files changed, 92 insertions(+)
>
> diff --git a/fs/iomap.c b/fs/iomap.c
> index 4b10892..781f0a0 100644
> --- a/fs/iomap.c
> +++ b/fs/iomap.c
> @@ -584,6 +584,95 @@ int iomap_fiemap(struct inode *inode, struct
> fiemap_extent_info *fi,
> }
> EXPORT_SYMBOL_GPL(iomap_fiemap);
>
> +static loff_t
> +iomap_seek_hole_actor(struct inode *inode, loff_t offset, loff_t length,
> + void *data, struct iomap *iomap)
> +{
> + if (iomap->type == IOMAP_HOLE)
> + goto found;
> + length = iomap->offset + iomap->length - offset;
What is the problem with the passed in length value?
> + if (iomap->type != IOMAP_UNWRITTEN)
> + return length;
> + offset = page_cache_seek_hole_data(inode, offset, length, SEEK_HOLE);
> + if (offset < 0)
> + return length;
> +found:
> + *(loff_t *)data = offset;
> + return 0;
What about using a switch statement?
switch (iomap->type) {
case IOMAP_UNWRITTEN:
offset = page_cache_seek_hole_data(inode, offset, length,
SEEK_HOLE);
if (offset < 0)
return length;
/*FALLTHRU*/
case IOMAP_HOLE:
*(loff_t *)data = offset;
return 0;
default:
return length;
}
> +static loff_t
> +iomap_seek_data_actor(struct inode *inode, loff_t offset, loff_t length,
> + void *data, struct iomap *iomap)
> +{
> + if (iomap->type != IOMAP_HOLE && iomap->type != IOMAP_UNWRITTEN)
> + goto found;
> + length = iomap->offset + iomap->length - offset;
> + if (iomap->type != IOMAP_UNWRITTEN)
> + return length;
> + offset = page_cache_seek_hole_data(inode, offset, length, SEEK_DATA);
> + if (offset < 0)
> + return length;
> +found:
> + *(loff_t *)data = offset;
> + return 0;
> +loff_t
> +iomap_seek_hole_data(struct inode *inode, loff_t offset,
> + int whence, const struct iomap_ops *ops)
> +{
> + static loff_t (*actor)(struct inode *, loff_t, loff_t, void *,
> + struct iomap *);
I wonder (but I'm not sure) if it would be simpler and easier to
understand to just have to different functions for SEEK_HOLE
vs SEEK_DATA here.
