[4/6] vfs: Add iomap_seek_hole and iomap_seek_data helpers

Message ID 20170627214828.1029-5-hch@lst.de
State Superseded
Headers show

Commit Message

Christoph Hellwig June 27, 2017, 9:48 p.m.
From: Andreas Gruenbacher <agruenba@redhat.com>

Filesystems can use this for implementing lseek SEEK_HOLE / SEEK_DATA
support via iomap.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
[hch: split functions, coding style cleanups]
Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 fs/iomap.c            | 98 +++++++++++++++++++++++++++++++++++++++++++++++++++
 include/linux/iomap.h |  4 +++
 2 files changed, 102 insertions(+)

Comments

Andreas Gr├╝nbacher June 27, 2017, 10:14 p.m. | #1
2017-06-27 23:48 GMT+02:00 Christoph Hellwig <hch@lst.de>:
> From: Andreas Gruenbacher <agruenba@redhat.com>
>
> Filesystems can use this for implementing lseek SEEK_HOLE / SEEK_DATA
> support via iomap.
>
> Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
> [hch: split functions, coding style cleanups]
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
>  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

Patch

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);
+	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. */
+	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: