Allow to create a loopback cdev from a file.
Signed-off-by: Philipp Zabel <p.za...@pengutronix.de>
---
fs/devfs-core.c | 81 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
fs/fs.c | 21 ++++++++++++---
include/driver.h | 1 +
3 files changed, 99 insertions(+), 4 deletions(-)
diff --git a/fs/devfs-core.c b/fs/devfs-core.c
index 382606f1cf..7ffa1e4327 100644
--- a/fs/devfs-core.c
+++ b/fs/devfs-core.c
@@ -20,11 +20,14 @@
#include <complete.h>
#include <driver.h>
#include <errno.h>
+#include <fcntl.h>
#include <malloc.h>
#include <ioctl.h>
#include <nand.h>
#include <linux/err.h>
+#include <linux/fs.h>
#include <linux/mtd/mtd.h>
+#include <unistd.h>
LIST_HEAD(cdev_list);
@@ -407,3 +410,81 @@ int devfs_create_partitions(const char *devname,
return 0;
}
+
+struct loop_priv {
+ int fd;
+};
+
+static ssize_t loop_read(struct cdev *cdev, void *buf, size_t count,
+ loff_t offset, ulong flags)
+{
+ struct loop_priv *priv = cdev->priv;
+ loff_t ofs;
+
+ ofs = lseek(priv->fd, offset, SEEK_SET);
+ if (ofs < 0)
+ return ofs;
+
+ return read(priv->fd, buf, count);
+}
+
+static ssize_t loop_write(struct cdev *cdev, const void *buf, size_t count,
+ loff_t offset, ulong flags)
+{
+ struct loop_priv *priv = cdev->priv;
+ loff_t ofs;
+
+ ofs = lseek(priv->fd, offset, SEEK_SET);
+ if (ofs < 0)
+ return ofs;
+
+ return write(priv->fd, buf, count);
+}
+
+static const struct file_operations loop_ops = {
+ .read = loop_read,
+ .write = loop_write,
+ .memmap = generic_memmap_rw,
+ .lseek = dev_lseek_default,
+};
+
+struct cdev *cdev_create_from_file(const char *path, ulong flags)
+{
+ struct cdev *new;
+ struct loop_priv *priv;
+ static int loopno;
+ loff_t ofs;
+
+ priv = xzalloc(sizeof(*priv));
+
+ priv->fd = open(path, flags);
+ if (priv->fd < 0) {
+ free(priv);
+ return NULL;
+ }
+
+ new = xzalloc(sizeof(*new));
+
+ new->name = strdup(path);
+
+ new->ops = &loop_ops;
+ new->name = basprintf("loop%u", loopno);
+ new->priv = priv;
+
+ ofs = lseek(priv->fd, 0, SEEK_END);
+ if (ofs < 0) {
+ free(new);
+ free(priv);
+ return NULL;
+ }
+ lseek(priv->fd, 0, SEEK_SET);
+
+ new->size = ofs;
+ new->offset = 0;
+ new->dev = NULL;
+ new->flags = 0;
+
+ devfs_create(new);
+
+ return new;
+}
diff --git a/fs/fs.c b/fs/fs.c
index 1901c94ad1..621ea19749 100644
--- a/fs/fs.c
+++ b/fs/fs.c
@@ -36,6 +36,8 @@
#include <block.h>
#include <libfile.h>
+#include "parseopt.h"
+
char *mkmodestr(unsigned long mode, char *str)
{
static const char *l = "xwr";
@@ -1222,13 +1224,18 @@ int register_fs_driver(struct fs_driver_d *fsdrv)
}
EXPORT_SYMBOL(register_fs_driver);
-static const char *detect_fs(const char *filename)
+static const char *detect_fs(const char *filename, const char *fsoptions)
{
enum filetype type;
struct driver_d *drv;
struct fs_driver_d *fdrv;
+ bool loop;
- type = cdev_detect_type(filename);
+ parseopt_b(fsoptions, "loop", &loop);
+ if (loop)
+ type = file_name_detect_type(filename);
+ else
+ type = cdev_detect_type(filename);
if (type == filetype_unknown)
return NULL;
@@ -1245,7 +1252,13 @@ static const char *detect_fs(const char *filename)
int fsdev_open_cdev(struct fs_device_d *fsdev)
{
- fsdev->cdev = cdev_open(fsdev->backingstore, O_RDWR);
+ bool loop;
+
+ parseopt_b(fsdev->options, "loop", &loop);
+ if (loop)
+ fsdev->cdev = cdev_create_from_file(fsdev->backingstore,
O_RDWR);
+ else
+ fsdev->cdev = cdev_open(fsdev->backingstore, O_RDWR);
if (!fsdev->cdev)
return -EINVAL;
@@ -1292,7 +1305,7 @@ int mount(const char *device, const char *fsname, const
char *_path,
}
if (!fsname)
- fsname = detect_fs(device);
+ fsname = detect_fs(device, fsoptions);
if (!fsname)
return -ENOENT;
diff --git a/include/driver.h b/include/driver.h
index 086e44636b..daa9453a3b 100644
--- a/include/driver.h
+++ b/include/driver.h
@@ -473,6 +473,7 @@ struct cdev *lcdev_by_name(const char *filename);
struct cdev *cdev_readlink(struct cdev *cdev);
struct cdev *cdev_by_device_node(struct device_node *node);
struct cdev *cdev_open(const char *name, unsigned long flags);
+struct cdev *cdev_create_from_file(const char *path, ulong flags);
int cdev_do_open(struct cdev *, unsigned long flags);
void cdev_close(struct cdev *cdev);
int cdev_flush(struct cdev *cdev);
--
2.11.0
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