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init/do_mounts.c: add root=PARTLABEL=<name> support 

Support referencing the root partition label from GPT as argument
to the root= option on the kernel command line in analogy to
referencing the partition uuid as root=PARTUUID=<uuid>.

Specifying the partition label instead of the uuid is often much
easier, e.g. in embedded environments when there is an
A/B rootfs partition scheme for interruptible firmware updates
(i.e. rootfsA/ rootfsB).

The partition label can be queried with the blkid command.

Link: http://lkml.kernel.org/r/20180822060904.828E510665E@pc-niv.weinmann.com
Signed-off-by: Nikolaus Voss <nikolaus.voss@loewensteinmedical.de>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Dominik Brodowski <linux@dominikbrodowski.net>
Cc: Sasha Levin <Alexander.Levin@microsoft.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Nikolaus Voss 2018-10-30 15:05:57 -07:00 committed by Linus Torvalds
parent 22ebb72b32
commit f027c34d84
1 changed files with 31 additions and 0 deletions
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31
init/do_mounts.c
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@ -167,6 +167,24 @@ static dev_t devt_from_partuuid(const char *uuid_str)
}
return res;
}
/**
* match_dev_by_label - callback for finding a partition using its label
* @dev: device passed in by the caller
* @data: opaque pointer to the label to match
*
* Returns 1 if the device matches, and 0 otherwise.
*/
static int match_dev_by_label(struct device *dev, const void *data)
{
const char *label = data;
struct hd_struct *part = dev_to_part(dev);
if (part->info && !strcmp(label, part->info->volname))
return 1;
return 0;
}
#endif
/*
@ -190,6 +208,8 @@ static dev_t devt_from_partuuid(const char *uuid_str)
* a partition with a known unique id.
* 8) <major>:<minor> major and minor number of the device separated by
* a colon.
* 9) PARTLABEL=<name> with name being the GPT partition label.
* MSDOS partitions do not support labels!
*
* If name doesn't have fall into the categories above, we return (0,0).
* block_class is used to check if something is a disk name. If the disk
@ -211,6 +231,17 @@ dev_t name_to_dev_t(const char *name)
if (!res)
goto fail;
goto done;
} else if (strncmp(name, "PARTLABEL=", 10) == 0) {
struct device *dev;
dev = class_find_device(&block_class, NULL, name + 10,
&match_dev_by_label);
if (!dev)
goto fail;
res = dev->devt;
put_device(dev);
goto done;
}
#endif