Filesystems can use this for implementing lseek SEEK_HOLE / SEEK_DATA
support via iomap.
Signed-off-by: Andreas Gruenbacher <agruenba@xxxxxxxxxx>
---
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;
+ 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;
+}
+
+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;
+}
+
+/*
+ * Filesystem helper for lseek SEEK_HOLE / SEEK_DATA.
+ */
+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 *);
+ loff_t size = i_size_read(inode);
+ loff_t length;
+
+ /* Nothing to be found beyond the end of the file. */
+ if (offset >= size)
+ return -ENXIO;
+ length = size - offset;
+
+ switch(whence) {
+ case SEEK_HOLE:
+ actor = iomap_seek_hole_actor;
+ break;
+
+ case SEEK_DATA:
+ actor = iomap_seek_data_actor;
+ break;
+ }
+
+ while (length > 0) {
+ loff_t ret;
+
+ ret = iomap_apply(inode, offset, length, IOMAP_REPORT, ops,
+ &offset, actor);
+ if (ret <= 0) {
+ if (ret < 0)
+ return ret;
+ break;
+ }
+ offset += ret;
+ length -= ret;
+ }
+
+ if (length <= 0) {
+ /* There is an implicit hole at the end of the file. */
+ if (whence != SEEK_HOLE)
+ return -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);
+
/*
* 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 f753e78..ff89026 100644
--- a/include/linux/iomap.h
+++ b/include/linux/iomap.h
@@ -83,6 +83,9 @@ 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_data(struct inode *inode, loff_t offset,
+ int whence, const struct iomap_ops *ops);
+
/*
* Flags for direct I/O ->end_io:
--
2.7.5
--
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