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Subject[patch 01/50] block: do_mounts - accept root=<non-existant partition>
-stable review patch.  If anyone has any objections, please let us know.
---------------------

From: Kay Sievers <kay.sievers@vrfy.org>

commit 30f2f0eb4bd2c43d10a8b0d872c6e5ad8f31c9a0 upstream

Some devices, like md, may create partitions only at first access,
so allow root= to be set to a valid non-existant partition of an
existing disk. This applies only to non-initramfs root mounting.

This fixes a regression from 2.6.24 which did allow this to happen and
broke some users machines :(

Acked-by: Neil Brown <neilb@suse.de>
Tested-by: Joao Luis Meloni Assirati <assirati@nonada.if.usp.br>
Signed-off-by: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Chris Wright <chrisw@sous-sol.org>

---
block/genhd.c | 9 ++++++---
include/linux/genhd.h | 4 ++--
init/do_mounts.c | 27 ++++++++++++++++++++++++++-
3 files changed, 34 insertions(+), 6 deletions(-)

--- a/block/genhd.c
+++ b/block/genhd.c
@@ -645,7 +645,7 @@ void genhd_media_change_notify(struct ge
EXPORT_SYMBOL_GPL(genhd_media_change_notify);
#endif /* 0 */

-dev_t blk_lookup_devt(const char *name)
+dev_t blk_lookup_devt(const char *name, int part)
{
struct device *dev;
dev_t devt = MKDEV(0, 0);
@@ -653,7 +653,11 @@ dev_t blk_lookup_devt(const char *name)
mutex_lock(&block_class_lock);
list_for_each_entry(dev, &block_class.devices, node) {
if (strcmp(dev->bus_id, name) == 0) {
- devt = dev->devt;
+ struct gendisk *disk = dev_to_disk(dev);
+
+ if (part < disk->minors)
+ devt = MKDEV(MAJOR(dev->devt),
+ MINOR(dev->devt) + part);
break;
}
}
@@ -661,7 +665,6 @@ dev_t blk_lookup_devt(const char *name)

return devt;
}
-
EXPORT_SYMBOL(blk_lookup_devt);

struct gendisk *alloc_disk(int minors)
--- a/include/linux/genhd.h
+++ b/include/linux/genhd.h
@@ -524,7 +524,7 @@ struct unixware_disklabel {
#define ADDPART_FLAG_RAID 1
#define ADDPART_FLAG_WHOLEDISK 2

-extern dev_t blk_lookup_devt(const char *name);
+extern dev_t blk_lookup_devt(const char *name, int part);
extern char *disk_name (struct gendisk *hd, int part, char *buf);

extern int rescan_partitions(struct gendisk *disk, struct block_device *bdev);
@@ -552,7 +552,7 @@ static inline struct block_device *bdget

static inline void printk_all_partitions(void) { }

-static inline dev_t blk_lookup_devt(const char *name)
+static inline dev_t blk_lookup_devt(const char *name, int part)
{
dev_t devt = MKDEV(0, 0);
return devt;
--- a/init/do_mounts.c
+++ b/init/do_mounts.c
@@ -76,6 +76,7 @@ dev_t name_to_dev_t(char *name)
char s[32];
char *p;
dev_t res = 0;
+ int part;

if (strncmp(name, "/dev/", 5) != 0) {
unsigned maj, min;
@@ -106,7 +107,31 @@ dev_t name_to_dev_t(char *name)
for (p = s; *p; p++)
if (*p == '/')
*p = '!';
- res = blk_lookup_devt(s);
+ res = blk_lookup_devt(s, 0);
+ if (res)
+ goto done;
+
+ /*
+ * try non-existant, but valid partition, which may only exist
+ * after revalidating the disk, like partitioned md devices
+ */
+ while (p > s && isdigit(p[-1]))
+ p--;
+ if (p == s || !*p || *p == '0')
+ goto fail;
+
+ /* try disk name without <part number> */
+ part = simple_strtoul(p, NULL, 10);
+ *p = '\0';
+ res = blk_lookup_devt(s, part);
+ if (res)
+ goto done;
+
+ /* try disk name without p<part number> */
+ if (p < s + 2 || !isdigit(p[-2]) || p[-1] != 'p')
+ goto fail;
+ p[-1] = '\0';
+ res = blk_lookup_devt(s, part);
if (res)
goto done;

--


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