From 87aa4832f7f3587a65ee92ffa24f528652684c1b Mon Sep 17 00:00:00 2001 From: Philipp Zabel Date: Thu, 1 Feb 2018 11:37:17 +0100 Subject: fs: add support loop mount offset When loop mounting, allow to specify an offset into the file, similarly to the losetup offset option. Multiplicative suffixes are supported. Signed-off-by: Philipp Zabel Signed-off-by: Sascha Hauer --- fs/devfs-core.c | 8 ++++---- fs/fs.c | 12 +++++++++--- include/driver.h | 2 +- 3 files changed, 14 insertions(+), 8 deletions(-) diff --git a/fs/devfs-core.c b/fs/devfs-core.c index be56edd18d..ea5887c720 100644 --- a/fs/devfs-core.c +++ b/fs/devfs-core.c @@ -464,7 +464,7 @@ static const struct file_operations loop_ops = { .lseek = dev_lseek_default, }; -struct cdev *cdev_create_loop(const char *path, ulong flags) +struct cdev *cdev_create_loop(const char *path, ulong flags, loff_t offset) { struct cdev *new; struct loop_priv *priv; @@ -486,15 +486,15 @@ struct cdev *cdev_create_loop(const char *path, ulong flags) new->priv = priv; ofs = lseek(priv->fd, 0, SEEK_END); - if (ofs < 0) { + if (ofs < 0 || ofs <= offset) { free(new); free(priv); return NULL; } - lseek(priv->fd, 0, SEEK_SET); + lseek(priv->fd, offset, SEEK_SET); new->size = ofs; - new->offset = 0; + new->offset = offset; new->dev = NULL; new->flags = 0; diff --git a/fs/fs.c b/fs/fs.c index 7d0d97906d..d188fa995f 100644 --- a/fs/fs.c +++ b/fs/fs.c @@ -1279,11 +1279,13 @@ 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; + bool loop = false; + unsigned long long offset = 0; parseopt_b(fsoptions, "loop", &loop); + parseopt_llu_suffix(fsoptions, "offset", &offset); if (loop) - type = file_name_detect_type(filename); + type = file_name_detect_type_offset(filename, offset); else type = cdev_detect_type(filename); @@ -1302,9 +1304,13 @@ static const char *detect_fs(const char *filename, const char *fsoptions) int fsdev_open_cdev(struct fs_device_d *fsdev) { + unsigned long long offset = 0; + parseopt_b(fsdev->options, "loop", &fsdev->loop); + parseopt_llu_suffix(fsdev->options, "offset", &offset); if (fsdev->loop) - fsdev->cdev = cdev_create_loop(fsdev->backingstore, O_RDWR); + fsdev->cdev = cdev_create_loop(fsdev->backingstore, O_RDWR, + offset); else fsdev->cdev = cdev_open(fsdev->backingstore, O_RDWR); if (!fsdev->cdev) diff --git a/include/driver.h b/include/driver.h index e571fbbec5..f37805db17 100644 --- a/include/driver.h +++ b/include/driver.h @@ -475,7 +475,7 @@ struct cdev *cdev_readlink(struct cdev *cdev); struct cdev *cdev_by_device_node(struct device_node *node); struct cdev *cdev_by_partuuid(const char *partuuid); struct cdev *cdev_open(const char *name, unsigned long flags); -struct cdev *cdev_create_loop(const char *path, ulong flags); +struct cdev *cdev_create_loop(const char *path, ulong flags, loff_t offset); void cdev_remove_loop(struct cdev *cdev); int cdev_do_open(struct cdev *, unsigned long flags); void cdev_close(struct cdev *cdev); -- cgit v1.2.3