On Fri, Jun 16, 2017 at 04:51:17PM +0200, Andreas Gruenbacher wrote:
> Filesystems can use this for implementing lseek SEEK_HOLE / SEEK_DATA
> support via iomap.
>
> The __iomap_seek_hole_data helper takes an additional size argument and
> doesn't reposition the file offset; this is for internal use for xfs
> quota files which don't maintain the inode size.
>
> Signed-off-by: Andreas Gruenbacher <agruenba@xxxxxxxxxx>
> ---
> fs/iomap.c | 81 +++++++++++++++++++++++++++++++++++++++++++++++++++
> include/linux/iomap.h | 6 ++++
> 2 files changed, 87 insertions(+)
>
> diff --git a/fs/iomap.c b/fs/iomap.c
> index 4b10892..cf01694 100644
> --- a/fs/iomap.c
> +++ b/fs/iomap.c
> @@ -584,6 +584,87 @@ 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)
Echoing Dave's comments further on (sorry, I tend to read the patchset but
reply in reverse order, distractions notwithstanding), for SEEK_{HOLE,DATA}
you'd want to test for type == IOMAP_HOLE || type == IOMAP_UNWRITTEN since
unwritten (i.e. fallocated) areas are treated as holes.
--D
> + return 0;
> + return iomap->offset + iomap->length - offset;
> +}
> +
> +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)
> + return 0;
> + return iomap->offset + iomap->length - offset;
> +}
> +
> +loff_t
> +__iomap_seek_hole_data(struct inode *inode, loff_t offset, loff_t size,
> + int whence, const struct iomap_ops *ops)
> +{
> + static loff_t (*actor)(struct inode *, loff_t, loff_t, void *,
> + struct iomap *);
> + loff_t len = size - offset;
> + loff_t ret;
> +
> + /* Nothing to be found beyond the end of the file. */
> + if (len <= 0)
> + return -ENXIO;
> +
> + switch(whence) {
> + case SEEK_HOLE:
> + actor = iomap_seek_hole_actor;
> + break;
> +
> + case SEEK_DATA:
> + actor = iomap_seek_data_actor;
> + break;
> + }
> +
> + while (len > 0) {
> + ret = iomap_apply(inode, offset, len, IOMAP_REPORT, ops,
> + NULL, actor);
> + if (ret <= 0) {
> + if (ret < 0)
> + return ret;
> + break;
> + }
> + offset += ret;
> + len -= ret;
> + }
> +
> + if (len <= 0) {
> + /* There is an implicit hole at the end of the file. */
> + if (whence != SEEK_HOLE)
> + offset = -ENXIO;
> +
> + /* The last segment can extend beyond the end of the file. */
> + if (offset > size)
> + offset = size;
> + }
> +
> + return offset;
> +}
> +EXPORT_SYMBOL_GPL(__iomap_seek_hole_data);
> +
> +loff_t
> +iomap_seek_hole_data(struct file *file, loff_t offset, int whence,
> + const struct iomap_ops *ops)
> +{
> + struct inode *inode = file->f_mapping->host;
> +
> + offset = __iomap_seek_hole_data(inode, offset, i_size_read(inode),
> + whence, ops);
> + if (offset <= 0)
> + return offset;
> + return vfs_setpos(file, offset, inode->i_sb->s_maxbytes);
> +}
> +EXPORT_SYMBOL_GPL(iomap_seek_hole_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 9d64933..49b6ec0 100644
> --- a/include/linux/iomap.h
> +++ b/include/linux/iomap.h
> @@ -85,6 +85,12 @@ 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);
>
> +struct file;
> +loff_t __iomap_seek_hole_data(struct inode *inode, loff_t pos, loff_t size,
> + int whence, const struct iomap_ops *ops);
> +loff_t iomap_seek_hole_data(struct file *file, loff_t pos,
> + int whence, const struct iomap_ops *ops);
> +
> /*
> * Flags for direct I/O ->end_io:
> */
> --
> 2.7.5
>
