[PATCH] discover: Handle BTRFS root subvolumes
Cyril Bur
cyril.bur at au1.ibm.com
Fri Jan 8 10:39:06 AEDT 2016
On Tue, 5 Jan 2016 16:47:01 +1100
Sam Mendoza-Jonas <sam at mendozajonas.com> wrote:
> During install some distributions[0] will create subvolumes when formatting
> the root filesystem with BTRFS. In particular this can mean that
> bootloader config files will appear (in the case of GRUB) under
> /var/petitboot/mnt/dev/$device/@/boot/grub/
> rather than the expected
> /var/petitboot/mnt/dev/$device/boot/grub/
>
> If this is the case, perform all file operations from the parser
> relative to this subvolume rather than the mount point. At the moment
> this only supports the trivial case where the subvolume name for root is
> blank (ie. '@').
>
I'm going to gloss over the total awkwardness of the whole process and $reasons
and such and say that since petitboot will struggle with newer ubuntu then...
on balance this kinda has to go in...
> [0] In particular, Ubuntu from at least 14.04
>
> Signed-off-by: Sam Mendoza-Jonas <sam at mendozajonas.com>
Reviewed-by: Cyril Bur <cyrilbur at gmail.com>
> ---
> discover/device-handler.c | 25 +++++++++++++++++++++++++
> discover/device-handler.h | 1 +
> discover/parser.c | 2 +-
> 3 files changed, 27 insertions(+), 1 deletion(-)
>
> diff --git a/discover/device-handler.c b/discover/device-handler.c
> index 5df0700..77f9e3c 100644
> --- a/discover/device-handler.c
> +++ b/discover/device-handler.c
> @@ -1285,6 +1285,28 @@ static inline const char *get_device_path(struct discover_device *dev)
> return dev->ramdisk ? dev->ramdisk->snapshot : dev->device_path;
> }
>
> +static char *check_subvols(struct discover_device *dev)
> +{
> + const char *fstype = discover_device_get_param(dev, "ID_FS_TYPE");
> + struct stat sb;
> + char *path;
> + int rc;
> +
> + if (strncmp(fstype, "btrfs", strlen("btrfs")))
> + return dev->mount_path;
> +
> + /* On btrfs a device's root may be under a subvolume path */
> + path = join_paths(dev, dev->mount_path, "@");
> + rc = stat(path, &sb);
> + if (!rc && S_ISDIR(sb.st_mode)) {
> + pb_debug("Using '%s' for btrfs root path\n", path);
> + return path;
> + }
> +
> + talloc_free(path);
> + return dev->mount_path;
> +}
> +
> static bool check_existing_mount(struct discover_device *dev)
> {
> struct stat devstat, mntstat;
> @@ -1326,6 +1348,7 @@ static bool check_existing_mount(struct discover_device *dev)
>
> if (mntstat.st_rdev == devstat.st_rdev) {
> dev->mount_path = talloc_strdup(dev, mnt->mnt_dir);
> + dev->root_path = check_subvols(dev);
> dev->mounted_rw = !!hasmntopt(mnt, "rw");
> dev->mounted = true;
> dev->unmount = false;
> @@ -1388,6 +1411,7 @@ static int mount_device(struct discover_device *dev)
> dev->mounted = true;
> dev->mounted_rw = false;
> dev->unmount = true;
> + dev->root_path = check_subvols(dev);
> return 0;
> }
>
> @@ -1426,6 +1450,7 @@ static int umount_device(struct discover_device *dev)
>
> talloc_free(dev->mount_path);
> dev->mount_path = NULL;
> + dev->root_path = NULL;
>
> return 0;
> }
> diff --git a/discover/device-handler.h b/discover/device-handler.h
> index e5501ec..12f5ce0 100644
> --- a/discover/device-handler.h
> +++ b/discover/device-handler.h
> @@ -25,6 +25,7 @@ struct discover_device {
> const char *label;
>
> char *mount_path;
> + char *root_path;
> const char *device_path;
> struct ramdisk_device *ramdisk;
> bool mounted;
> diff --git a/discover/parser.c b/discover/parser.c
> index 8e767c6..fbf31b2 100644
> --- a/discover/parser.c
> +++ b/discover/parser.c
> @@ -25,7 +25,7 @@ static char *local_path(struct discover_context *ctx,
> struct discover_device *dev,
> const char *filename)
> {
> - return join_paths(ctx, dev->mount_path, filename);
> + return join_paths(ctx, dev->root_path, filename);
> }
>
> int parser_request_file(struct discover_context *ctx,
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