2017-06-27 23:48 GMT+02:00 Christoph Hellwig <hch@xxxxxx>:
> From: Andreas Gruenbacher <agruenba@xxxxxxxxxx>
>
> Filesystems can use this for implementing lseek SEEK_HOLE / SEEK_DATA
> support via iomap.
>
> Signed-off-by: Andreas Gruenbacher <agruenba@xxxxxxxxxx>
> [hch: split functions, coding style cleanups]
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>
> ---
> fs/iomap.c | 98 +++++++++++++++++++++++++++++++++++++++++++++++++++
> include/linux/iomap.h | 4 +++
> 2 files changed, 102 insertions(+)
>
> diff --git a/fs/iomap.c b/fs/iomap.c
> index 4b10892967a5..c90cda33994b 100644
> --- a/fs/iomap.c
> +++ b/fs/iomap.c
> @@ -584,6 +584,104 @@ 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)
> +{
> + switch (iomap->type) {
> + case IOMAP_UNWRITTEN:
> + offset = page_cache_seek_hole_data(inode, offset, length,
> + SEEK_HOLE);
> + if (offset < 0)
> + return length;
> + /* fall through */
> + case IOMAP_HOLE:
> + *(loff_t *)data = offset;
> + return 0;
> + default:
> + return length;
> + }
> +}
> +
> +loff_t
> +iomap_seek_hole(struct inode *inode, loff_t offset, const struct iomap_ops *ops)
> +{
> + loff_t size = i_size_read(inode);
> + loff_t length = size - offset;
> + loff_t ret;
> +
> + /* Nothing to be found beyond the end of the file. */
> + if (offset >= size)
> + return -ENXIO;
> +
> + while (length > 0) {
> + ret = iomap_apply(inode, offset, length, IOMAP_REPORT, ops,
> + &offset, iomap_seek_hole_actor);
> + if (ret < 0)
> + return ret;
> + if (ret == 0)
> + break;
> +
> + offset += ret;
> + length -= ret;
> + }
> +
> + /* The last segment can extend beyond the end of the file. */
> + if (length <= 0)
> + return min(offset, size);
This shouldn't be true anymore now that the actors don't recompute the
length; the above three lines should be obsolete.
> + return offset;
> +}
> +EXPORT_SYMBOL_GPL(iomap_seek_hole);
> +
> +static loff_t
> +iomap_seek_data_actor(struct inode *inode, loff_t offset, loff_t length,
> + void *data, struct iomap *iomap)
> +{
> + switch (iomap->type) {
> + case IOMAP_HOLE:
> + return length;
> + case IOMAP_UNWRITTEN:
> + offset = page_cache_seek_hole_data(inode, offset, length,
> + SEEK_DATA);
> + if (offset < 0)
> + return length;
> + /*FALLTHRU*/
> + default:
> + *(loff_t *)data = offset;
> + return 0;
> + }
> +}
> +
> +loff_t
> +iomap_seek_data(struct inode *inode, loff_t offset, const struct iomap_ops *ops)
> +{
> + loff_t size = i_size_read(inode);
> + loff_t length = size - offset;
> + loff_t ret;
> +
> + /* Nothing to be found beyond the end of the file. */
> + if (offset >= size)
> + return -ENXIO;
> +
> + while (length > 0) {
> + ret = iomap_apply(inode, offset, length, IOMAP_REPORT, ops,
> + &offset, iomap_seek_data_actor);
> + if (ret < 0)
> + return ret;
> + if (ret == 0)
> + break;
> +
> + offset += ret;
> + length -= ret;
> + }
> +
> + /* There is an implicit hole at the end of the file. */
This comment makes more sense in iomap_seek_hole now.
> + if (length <= 0)
> + return -ENXIO;
> + return offset;
> +}
> +EXPORT_SYMBOL_GPL(iomap_seek_data);
> +
> /*
> * Private flags for iomap_dio, must not overlap with the public ones in
> * iomap.h:
> diff --git a/include/linux/iomap.h b/include/linux/iomap.h
> index f753e788da31..8a03f5dcd89b 100644
> --- a/include/linux/iomap.h
> +++ b/include/linux/iomap.h
> @@ -83,6 +83,10 @@ int iomap_truncate_page(struct inode *inode, loff_t pos, bool *did_zero,
> int iomap_page_mkwrite(struct vm_fault *vmf, const struct iomap_ops *ops);
> int iomap_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
> loff_t start, loff_t len, const struct iomap_ops *ops);
> +loff_t iomap_seek_hole(struct inode *inode, loff_t offset,
> + const struct iomap_ops *ops);
> +loff_t iomap_seek_data(struct inode *inode, loff_t offset,
> + const struct iomap_ops *ops);
>
> /*
> * Flags for direct I/O ->end_io:
> --
> 2.11.0
Thanks,
Andreas
