block: do_mounts - accept root=<non-existant partition>

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>
Cc: stable <stable@kernel.org>
Signed-off-by: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/block/genhd.c b/block/genhd.c
index fda9c7a..129ad93 100644 (file)
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -653,7 +653,7 @@ void genhd_media_change_notify(struct gendisk *disk)
 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);
@@ -661,7 +661,11 @@ 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;
                }
        }
@@ -669,7 +673,6 @@ dev_t blk_lookup_devt(const char *name)
 
        return devt;
 }
-
 EXPORT_SYMBOL(blk_lookup_devt);
 
 struct gendisk *alloc_disk(int minors)

diff --git a/include/linux/genhd.h b/include/linux/genhd.h
index e9874e7..ae7aec3 100644 (file)
--- a/include/linux/genhd.h
+++ b/include/linux/genhd.h
@@ -525,7 +525,7 @@ 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);
@@ -553,7 +553,7 @@ static inline struct block_device *bdget_disk(struct gendisk *disk, int index)
 
 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;

diff --git a/init/do_mounts.c b/init/do_mounts.c
index 3885e70..660c1e5 100644 (file)
--- 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;