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authorTejun Heo <tj@kernel.org>2008-08-25 19:47:25 +0900
committerJens Axboe <jens.axboe@oracle.com>2008-10-09 08:56:06 +0200
commit870d6656126add8e383645732b03df2b7ccd4f94 (patch)
tree9c33dd91350ea163b160d9f5cb40d913c5caf268
parentf615b48cc7df7cac3865ec76ac1a5bb04d3e07f4 (diff)
block: implement CONFIG_DEBUG_BLOCK_EXT_DEVT
Extended devt introduces non-contiguos device numbers. This patch implements a debug option which forces most devt allocations to be from the extended area and spreads them out. This is enabled by default if DEBUG_KERNEL is set and achieves... 1. Detects code paths in kernel or userland which expect predetermined consecutive device numbers. 2. When something goes wrong, avoid corruption as adding to the minor of earlier partition won't lead to the wrong but valid device. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
-rw-r--r--block/genhd.c38
-rw-r--r--drivers/ide/ide-disk.c6
-rw-r--r--drivers/scsi/sd.c6
-rw-r--r--lib/Kconfig.debug16
4 files changed, 63 insertions, 3 deletions
diff --git a/block/genhd.c b/block/genhd.c
index ee4b13520e5..67e5a59ced2 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -299,6 +299,38 @@ EXPORT_SYMBOL(unregister_blkdev);
static struct kobj_map *bdev_map;
/**
+ * blk_mangle_minor - scatter minor numbers apart
+ * @minor: minor number to mangle
+ *
+ * Scatter consecutively allocated @minor number apart if MANGLE_DEVT
+ * is enabled. Mangling twice gives the original value.
+ *
+ * RETURNS:
+ * Mangled value.
+ *
+ * CONTEXT:
+ * Don't care.
+ */
+static int blk_mangle_minor(int minor)
+{
+#ifdef CONFIG_DEBUG_BLOCK_EXT_DEVT
+ int i;
+
+ for (i = 0; i < MINORBITS / 2; i++) {
+ int low = minor & (1 << i);
+ int high = minor & (1 << (MINORBITS - 1 - i));
+ int distance = MINORBITS - 1 - 2 * i;
+
+ minor ^= low | high; /* clear both bits */
+ low <<= distance; /* swap the positions */
+ high >>= distance;
+ minor |= low | high; /* and set */
+ }
+#endif
+ return minor;
+}
+
+/**
* blk_alloc_devt - allocate a dev_t for a partition
* @part: partition to allocate dev_t for
* @gfp_mask: memory allocation flag
@@ -339,7 +371,7 @@ int blk_alloc_devt(struct hd_struct *part, dev_t *devt)
return -EBUSY;
}
- *devt = MKDEV(BLOCK_EXT_MAJOR, idx);
+ *devt = MKDEV(BLOCK_EXT_MAJOR, blk_mangle_minor(idx));
return 0;
}
@@ -361,7 +393,7 @@ void blk_free_devt(dev_t devt)
if (MAJOR(devt) == BLOCK_EXT_MAJOR) {
mutex_lock(&ext_devt_mutex);
- idr_remove(&ext_devt_idr, MINOR(devt));
+ idr_remove(&ext_devt_idr, blk_mangle_minor(MINOR(devt)));
mutex_unlock(&ext_devt_mutex);
}
}
@@ -473,7 +505,7 @@ struct gendisk *get_gendisk(dev_t devt, int *partno)
struct hd_struct *part;
mutex_lock(&ext_devt_mutex);
- part = idr_find(&ext_devt_idr, MINOR(devt));
+ part = idr_find(&ext_devt_idr, blk_mangle_minor(MINOR(devt)));
if (part && get_disk(part_to_disk(part))) {
*partno = part->partno;
disk = part_to_disk(part);
diff --git a/drivers/ide/ide-disk.c b/drivers/ide/ide-disk.c
index 7a88de9ada2..a072df5053a 100644
--- a/drivers/ide/ide-disk.c
+++ b/drivers/ide/ide-disk.c
@@ -42,7 +42,13 @@
#include <asm/div64.h>
#define IDE_DISK_PARTS (1 << PARTN_BITS)
+
+#if !defined(CONFIG_DEBUG_BLOCK_EXT_DEVT)
#define IDE_DISK_MINORS IDE_DISK_PARTS
+#else
+#define IDE_DISK_MINORS 1
+#endif
+
#define IDE_DISK_EXT_MINORS (IDE_DISK_PARTS - IDE_DISK_MINORS)
struct ide_disk_obj {
diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index d1bb0e1d2d2..280d231a86e 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -87,7 +87,13 @@ MODULE_ALIAS_SCSI_DEVICE(TYPE_MOD);
MODULE_ALIAS_SCSI_DEVICE(TYPE_RBC);
#define SD_PARTS 64
+
+#if !defined(CONFIG_DEBUG_BLOCK_EXT_DEVT)
#define SD_MINORS 16
+#else
+#define SD_MINORS 1
+#endif
+
#define SD_EXT_MINORS (SD_PARTS - SD_MINORS)
static int sd_revalidate_disk(struct gendisk *);
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 0b504814e37..5a536f703a8 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -624,6 +624,22 @@ config BACKTRACE_SELF_TEST
Say N if you are unsure.
+config DEBUG_BLOCK_EXT_DEVT
+ bool "Force extended block device numbers and spread them"
+ depends on DEBUG_KERNEL
+ depends on BLOCK
+ default y
+ help
+ Conventionally, block device numbers are allocated from
+ predetermined contiguous area. However, extended block area
+ may introduce non-contiguous block device numbers. This
+ option forces most block device numbers to be allocated from
+ the extended space and spreads them to discover kernel or
+ userland code paths which assume predetermined contiguous
+ device number allocation.
+
+ Say N if you are unsure.
+
config LKDTM
tristate "Linux Kernel Dump Test Tool Module"
depends on DEBUG_KERNEL