[PATCH 000 of 5] md: assorted bug fixes and minor features

[PATCH 000 of 5] md: assorted bug fixes and minor features

[NeilBrown]

Following are 5 patches for md suitable for 2.6.22.  None are needed for -stable.

Thanks
NeilBrown

 [PATCH 001 of 5] md: Move test for whether level supports bitmap to correct place.
 [PATCH 002 of 5] md: Stop using csum_partial for checksum calculation in md.
 [PATCH 003 of 5] md: Remove the slash from the name of a kmem_cache used by raid5.
 [PATCH 004 of 5] md: Allow reshape_position for md arrays to be set via sysfs.
 [PATCH 005 of 5] md: Improve partition detection in md array.

[PATCH 001 of 5] md: Move test for whether level supports bitmap to correct place.

[NeilBrown]

We need to check for internal-consistency of superblock in
load_super.  validate_super is for inter-device consistency.

With the test in the wrong place, a badly created array will confuse md
rather an produce sensible errors.

Signed-off-by: Neil Brown <neilb@suse.de>

### Diffstat output
 ./drivers/md/md.c |   42 ++++++++++++++++++++++++++----------------
 1 file changed, 26 insertions(+), 16 deletions(-)

diff .prev/drivers/md/md.c ./drivers/md/md.c
--- .prev/drivers/md/md.c	2007-05-07 14:33:31.000000000 +1000
+++ ./drivers/md/md.c	2007-05-07 14:33:31.000000000 +1000
@@ -695,6 +695,17 @@ static int super_90_load(mdk_rdev_t *rde
 	rdev->data_offset = 0;
 	rdev->sb_size = MD_SB_BYTES;
 
+	if (sb->state & (1<<MD_SB_BITMAP_PRESENT)) {
+		if (sb->level != 1 && sb->level != 4
+		    && sb->level != 5 && sb->level != 6
+		    && sb->level != 10) {
+			/* FIXME use a better test */
+			printk(KERN_WARNING
+			       "md: bitmaps not supported for this level.\n");
+			goto abort;
+		}
+	}
+
 	if (sb->level == LEVEL_MULTIPATH)
 		rdev->desc_nr = -1;
 	else
@@ -793,16 +804,8 @@ static int super_90_validate(mddev_t *md
 		mddev->max_disks = MD_SB_DISKS;
 
 		if (sb->state & (1<<MD_SB_BITMAP_PRESENT) &&
-		    mddev->bitmap_file == NULL) {
-			if (mddev->level != 1 && mddev->level != 4
-			    && mddev->level != 5 && mddev->level != 6
-			    && mddev->level != 10) {
-				/* FIXME use a better test */
-				printk(KERN_WARNING "md: bitmaps not supported for this level.\n");
-				return -EINVAL;
-			}
+		    mddev->bitmap_file == NULL)
 			mddev->bitmap_offset = mddev->default_bitmap_offset;
-		}
 
 	} else if (mddev->pers == NULL) {
 		/* Insist on good event counter while assembling */
@@ -1059,6 +1062,18 @@ static int super_1_load(mdk_rdev_t *rdev
 		       bdevname(rdev->bdev,b));
 		return -EINVAL;
 	}
+	if ((le32_to_cpu(sb->feature_map) & MD_FEATURE_BITMAP_OFFSET)) {
+		if (sb->level != cpu_to_le32(1) &&
+		    sb->level != cpu_to_le32(4) &&
+		    sb->level != cpu_to_le32(5) &&
+		    sb->level != cpu_to_le32(6) &&
+		    sb->level != cpu_to_le32(10)) {
+			printk(KERN_WARNING
+			       "md: bitmaps not supported for this level.\n");
+			return -EINVAL;
+		}
+	}
+
 	rdev->preferred_minor = 0xffff;
 	rdev->data_offset = le64_to_cpu(sb->data_offset);
 	atomic_set(&rdev->corrected_errors, le32_to_cpu(sb->cnt_corrected_read));
@@ -1142,14 +1157,9 @@ static int super_1_validate(mddev_t *mdd
 		mddev->max_disks =  (4096-256)/2;
 
 		if ((le32_to_cpu(sb->feature_map) & MD_FEATURE_BITMAP_OFFSET) &&
-		    mddev->bitmap_file == NULL ) {
-			if (mddev->level != 1 && mddev->level != 5 && mddev->level != 6
-			    && mddev->level != 10) {
-				printk(KERN_WARNING "md: bitmaps not supported for this level.\n");
-				return -EINVAL;
-			}
+		    mddev->bitmap_file == NULL )
 			mddev->bitmap_offset = (__s32)le32_to_cpu(sb->bitmap_offset);
-		}
+
 		if ((le32_to_cpu(sb->feature_map) & MD_FEATURE_RESHAPE_ACTIVE)) {
 			mddev->reshape_position = le64_to_cpu(sb->reshape_position);
 			mddev->delta_disks = le32_to_cpu(sb->delta_disks);

[PATCH 002 of 5] md: Stop using csum_partial for checksum calculation in md.

[NeilBrown]

If CONFIG_NET is not selected, csum_partial is not exported, so
md.ko cannot use it.
We shouldn't really be using csum_partial anyway as it is an
internal-to-networking interface.

So replace it with C code to do the same thing.  Speed is not
crucial here, so something simple and correct is best.

Signed-off-by: Neil Brown <neilb@suse.de>

### Diffstat output
 ./drivers/md/md.c |   31 +++++++++++++++++++++++++++++--
 1 file changed, 29 insertions(+), 2 deletions(-)

diff .prev/drivers/md/md.c ./drivers/md/md.c
--- .prev/drivers/md/md.c	2007-05-07 14:33:31.000000000 +1000
+++ ./drivers/md/md.c	2007-05-07 14:57:41.000000000 +1000
@@ -590,14 +590,41 @@ abort:
 	return ret;
 }
 
+
+static u32 md_csum_fold(u32 csum)
+{
+	csum = (csum & 0xffff) + (csum >> 16);
+	return (csum & 0xffff) + (csum >> 16);
+}
+
 static unsigned int calc_sb_csum(mdp_super_t * sb)
 {
+	u64 newcsum = 0;
+	u32 *sb32 = (u32*)sb;
+	int i;
 	unsigned int disk_csum, csum;
 
 	disk_csum = sb->sb_csum;
 	sb->sb_csum = 0;
-	csum = csum_partial((void *)sb, MD_SB_BYTES, 0);
+
+	for (i = 0; i < MD_SB_BYTES/4 ; i++)
+		newcsum += sb32[i];
+	csum = (newcsum & 0xffffffff) + (newcsum>>32);
+
+
+#ifdef CONFIG_ALPHA
+	/* This used to use csum_partial, which was wrong for several
+	 * reasons including that different results are returned on
+	 * different architectures.  It isn't critical that we get exactly
+	 * the same return value as before (we always csum_fold before
+	 * testing, and that removes any differences).  However as we
+	 * know that csum_partial always returned a 16bit value on
+	 * alphas, do a fold to maximise conformity to previous behaviour.
+	 */
+	sb->sb_csum = md_csum_fold(disk_csum);
+#else
 	sb->sb_csum = disk_csum;
+#endif
 	return csum;
 }
 
@@ -685,7 +712,7 @@ static int super_90_load(mdk_rdev_t *rde
 	if (sb->raid_disks <= 0)
 		goto abort;
 
-	if (csum_fold(calc_sb_csum(sb)) != csum_fold(sb->sb_csum)) {
+	if (md_csum_fold(calc_sb_csum(sb)) != md_csum_fold(sb->sb_csum)) {
 		printk(KERN_WARNING "md: invalid superblock checksum on %s\n",
 			b);
 		goto abort;

[PATCH 003 of 5] md: Remove the slash from the name of a kmem_cache used by raid5.

[NeilBrown]

SLUB doesn't like slashes as it wants to use the cache name
as the name of a directory (or symlink) in sysfs.

Signed-off-by: Neil Brown <neilb@suse.de>

### Diffstat output
 ./drivers/md/raid5.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff .prev/drivers/md/raid5.c ./drivers/md/raid5.c
--- .prev/drivers/md/raid5.c	2007-05-07 14:36:01.000000000 +1000
+++ ./drivers/md/raid5.c	2007-05-07 15:08:45.000000000 +1000
@@ -931,8 +931,8 @@ static int grow_stripes(raid5_conf_t *co
 	struct kmem_cache *sc;
 	int devs = conf->raid_disks;
 
-	sprintf(conf->cache_name[0], "raid5/%s", mdname(conf->mddev));
-	sprintf(conf->cache_name[1], "raid5/%s-alt", mdname(conf->mddev));
+	sprintf(conf->cache_name[0], "raid5-%s", mdname(conf->mddev));
+	sprintf(conf->cache_name[1], "raid5-%s-alt", mdname(conf->mddev));
 	conf->active_name = 0;
 	sc = kmem_cache_create(conf->cache_name[conf->active_name],
 			       sizeof(struct stripe_head)+(devs-1)*sizeof(struct r5dev),

[PATCH 004 of 5] md: Allow reshape_position for md arrays to be set via sysfs.

[NeilBrown]

"reshape_position" records how much progress has been made on a
"reshape" (adding drives, changing layout or chunksize).

When it is set, the number of drives, layout and chunksize can have
two possible values, an old an a new.

So allow these different values to be visible, and allow both old and
new to be set:  Set the old ones first, then the reshape_position,
then the new values.


Signed-off-by: Neil Brown <neilb@suse.de>

### Diffstat output
 ./Documentation/md.txt |   72 +++++++++++++++++++++++++++++--------------------
 ./drivers/md/md.c      |   70 ++++++++++++++++++++++++++++++++++++++++++-----
 2 files changed, 107 insertions(+), 35 deletions(-)

diff .prev/Documentation/md.txt ./Documentation/md.txt
--- .prev/Documentation/md.txt	2007-05-07 15:38:13.000000000 +1000
+++ ./Documentation/md.txt	2007-05-07 15:49:01.000000000 +1000
@@ -178,6 +178,21 @@ All md devices contain:
      The size should be at least PAGE_SIZE (4k) and should be a power
      of 2.  This can only be set while assembling an array
 
+  layout
+     The "layout" for the array for the particular level.  This is
+     simply a number that is interpretted differently by different
+     levels.  It can be written while assembling an array.
+
+  reshape_position
+     This is either "none" or a sector number within the devices of
+     the array where "reshape" is up to.  If this is set, the three
+     attributes mentioned above (raid_disks, chunk_size, layout) can
+     potentially have 2 values, an old and a new value.  If these
+     values differ, reading the attribute returns
+        new (old)
+     and writing will effect the 'new' value, leaving the 'old'
+     unchanged.
+
   component_size
      For arrays with data redundancy (i.e. not raid0, linear, faulty,
      multipath), all components must be the same size - or at least
@@ -193,11 +208,6 @@ All md devices contain:
      1.2 (newer format in varying locations) or "none" indicating that
      the kernel isn't managing metadata at all.
 
-  layout
-     The "layout" for the array for the particular level.  This is
-     simply a number that is interpretted differently by different
-     levels.  It can be written while assembling an array.
-
   resync_start
      The point at which resync should start.  If no resync is needed,
      this will be a very large number.  At array creation it will
@@ -259,29 +269,6 @@ All md devices contain:
          like active, but no writes have been seen for a while (safe_mode_delay).
 
 
-   sync_speed_min
-   sync_speed_max
-     This are similar to /proc/sys/dev/raid/speed_limit_{min,max}
-     however they only apply to the particular array.
-     If no value has been written to these, of if the word 'system'
-     is written, then the system-wide value is used.  If a value,
-     in kibibytes-per-second is written, then it is used.
-     When the files are read, they show the currently active value
-     followed by "(local)" or "(system)" depending on whether it is
-     a locally set or system-wide value.
-
-   sync_completed
-     This shows the number of sectors that have been completed of
-     whatever the current sync_action is, followed by the number of
-     sectors in total that could need to be processed.  The two
-     numbers are separated by a '/'  thus effectively showing one
-     value, a fraction of the process that is complete.
-
-   sync_speed
-     This shows the current actual speed, in K/sec, of the current
-     sync_action.  It is averaged over the last 30 seconds.
-
-
 As component devices are added to an md array, they appear in the 'md'
 directory as new directories named
       dev-XXX
@@ -412,6 +399,35 @@ also have
       Note that the numbers are 'bit' numbers, not 'block' numbers.
       They should be scaled by the bitmap_chunksize.
 
+   sync_speed_min
+   sync_speed_max
+     This are similar to /proc/sys/dev/raid/speed_limit_{min,max}
+     however they only apply to the particular array.
+     If no value has been written to these, of if the word 'system'
+     is written, then the system-wide value is used.  If a value,
+     in kibibytes-per-second is written, then it is used.
+     When the files are read, they show the currently active value
+     followed by "(local)" or "(system)" depending on whether it is
+     a locally set or system-wide value.
+
+   sync_completed
+     This shows the number of sectors that have been completed of
+     whatever the current sync_action is, followed by the number of
+     sectors in total that could need to be processed.  The two
+     numbers are separated by a '/'  thus effectively showing one
+     value, a fraction of the process that is complete.
+
+   sync_speed
+     This shows the current actual speed, in K/sec, of the current
+     sync_action.  It is averaged over the last 30 seconds.
+
+   suspend_lo
+   suspend_hi
+     The two values, given as numbers of sectors, indicate a range
+     within the array where IO will be blocked.  This is currently
+     only supported for raid4/5/6.
+
+
 Each active md device may also have attributes specific to the
 personality module that manages it.
 These are specific to the implementation of the module and could

diff .prev/drivers/md/md.c ./drivers/md/md.c
--- .prev/drivers/md/md.c	2007-05-07 14:57:41.000000000 +1000
+++ ./drivers/md/md.c	2007-05-07 15:18:16.000000000 +1000
@@ -274,6 +274,7 @@ static mddev_t * mddev_find(dev_t unit)
 	atomic_set(&new->active, 1);
 	spin_lock_init(&new->write_lock);
 	init_waitqueue_head(&new->sb_wait);
+	new->reshape_position = MaxSector;
 
 	new->queue = blk_alloc_queue(GFP_KERNEL);
 	if (!new->queue) {
@@ -2242,6 +2243,10 @@ static ssize_t
 layout_show(mddev_t *mddev, char *page)
 {
 	/* just a number, not meaningful for all levels */
+	if (mddev->reshape_position != MaxSector &&
+	    mddev->layout != mddev->new_layout)
+		return sprintf(page, "%d (%d)\n",
+			       mddev->new_layout, mddev->layout);
 	return sprintf(page, "%d\n", mddev->layout);
 }
 
@@ -2250,13 +2255,16 @@ layout_store(mddev_t *mddev, const char 
 {
 	char *e;
 	unsigned long n = simple_strtoul(buf, &e, 10);
-	if (mddev->pers)
-		return -EBUSY;
 
 	if (!*buf || (*e && *e != '\n'))
 		return -EINVAL;
 
-	mddev->layout = n;
+	if (mddev->pers)
+		return -EBUSY;
+	if (mddev->reshape_position != MaxSector)
+		mddev->new_layout = n;
+	else
+		mddev->layout = n;
 	return len;
 }
 static struct md_sysfs_entry md_layout =
@@ -2268,6 +2276,10 @@ raid_disks_show(mddev_t *mddev, char *pa
 {
 	if (mddev->raid_disks == 0)
 		return 0;
+	if (mddev->reshape_position != MaxSector &&
+	    mddev->delta_disks != 0)
+		return sprintf(page, "%d (%d)\n", mddev->raid_disks,
+			       mddev->raid_disks - mddev->delta_disks);
 	return sprintf(page, "%d\n", mddev->raid_disks);
 }
 
@@ -2285,7 +2297,11 @@ raid_disks_store(mddev_t *mddev, const c
 
 	if (mddev->pers)
 		rv = update_raid_disks(mddev, n);
-	else
+	else if (mddev->reshape_position != MaxSector) {
+		int olddisks = mddev->raid_disks - mddev->delta_disks;
+		mddev->delta_disks = n - olddisks;
+		mddev->raid_disks = n;
+	} else
 		mddev->raid_disks = n;
 	return rv ? rv : len;
 }
@@ -2295,6 +2311,10 @@ __ATTR(raid_disks, S_IRUGO|S_IWUSR, raid
 static ssize_t
 chunk_size_show(mddev_t *mddev, char *page)
 {
+	if (mddev->reshape_position != MaxSector &&
+	    mddev->chunk_size != mddev->new_chunk)
+		return sprintf(page, "%d (%d)\n", mddev->new_chunk,
+			       mddev->chunk_size);
 	return sprintf(page, "%d\n", mddev->chunk_size);
 }
 
@@ -2305,12 +2325,15 @@ chunk_size_store(mddev_t *mddev, const c
 	char *e;
 	unsigned long n = simple_strtoul(buf, &e, 10);
 
-	if (mddev->pers)
-		return -EBUSY;
 	if (!*buf || (*e && *e != '\n'))
 		return -EINVAL;
 
-	mddev->chunk_size = n;
+	if (mddev->pers)
+		return -EBUSY;
+	else if (mddev->reshape_position != MaxSector)
+		mddev->new_chunk = n;
+	else
+		mddev->chunk_size = n;
 	return len;
 }
 static struct md_sysfs_entry md_chunk_size =
@@ -2896,6 +2919,37 @@ suspend_hi_store(mddev_t *mddev, const c
 static struct md_sysfs_entry md_suspend_hi =
 __ATTR(suspend_hi, S_IRUGO|S_IWUSR, suspend_hi_show, suspend_hi_store);
 
+static ssize_t
+reshape_position_show(mddev_t *mddev, char *page)
+{
+	if (mddev->reshape_position != MaxSector)
+		return sprintf(page, "%llu\n",
+			       (unsigned long long)mddev->reshape_position);
+	strcpy(page, "none\n");
+	return 5;
+}
+
+static ssize_t
+reshape_position_store(mddev_t *mddev, const char *buf, size_t len)
+{
+	char *e;
+	unsigned long long new = simple_strtoull(buf, &e, 10);
+	if (mddev->pers)
+		return -EBUSY;
+	if (buf == e || (*e && *e != '\n'))
+		return -EINVAL;
+	mddev->reshape_position = new;
+	mddev->delta_disks = 0;
+	mddev->new_level = mddev->level;
+	mddev->new_layout = mddev->layout;
+	mddev->new_chunk = mddev->chunk_size;
+	return len;
+}
+
+static struct md_sysfs_entry md_reshape_position =
+__ATTR(reshape_position, S_IRUGO|S_IWUSR, reshape_position_show,
+       reshape_position_store);
+
 
 static struct attribute *md_default_attrs[] = {
 	&md_level.attr,
@@ -2908,6 +2962,7 @@ static struct attribute *md_default_attr
 	&md_new_device.attr,
 	&md_safe_delay.attr,
 	&md_array_state.attr,
+	&md_reshape_position.attr,
 	NULL,
 };
 
@@ -3446,6 +3501,7 @@ static int do_md_stop(mddev_t * mddev, i
 		mddev->size = 0;
 		mddev->raid_disks = 0;
 		mddev->recovery_cp = 0;
+		mddev->reshape_position = MaxSector;
 
 	} else if (mddev->pers)
 		printk(KERN_INFO "md: %s switched to read-only mode.\n",

[PATCH 005 of 5] md: Improve partition detection in md array.

[NeilBrown]

md currently uses ->media_changed to make sure rescan_partitions
is call on md array after they are assembled.

However that doesn't happen until the array is opened, which is later
than some people would like.

So use blkdev_ioctl to do the rescan immediately that the
array has been assembled.

This means we can remove all the ->change infrastructure as it was only used
to trigger a partition rescan.

Signed-off-by: Neil Brown <neilb@suse.de>

### Diffstat output
 ./drivers/md/md.c           |   26 ++++++++------------------
 ./drivers/md/raid1.c        |    1 -
 ./drivers/md/raid5.c        |    2 --
 ./include/linux/raid/md_k.h |    1 -
 4 files changed, 8 insertions(+), 22 deletions(-)

diff .prev/drivers/md/md.c ./drivers/md/md.c
--- .prev/drivers/md/md.c	2007-05-08 14:24:00.000000000 +1000
+++ ./drivers/md/md.c	2007-05-07 17:47:15.000000000 +1000
@@ -3104,6 +3104,7 @@ static int do_md_run(mddev_t * mddev)
 	struct gendisk *disk;
 	struct mdk_personality *pers;
 	char b[BDEVNAME_SIZE];
+	struct block_device *bdev;
 
 	if (list_empty(&mddev->disks))
 		/* cannot run an array with no devices.. */
@@ -3331,7 +3332,13 @@ static int do_md_run(mddev_t * mddev)
 	md_wakeup_thread(mddev->thread);
 	md_wakeup_thread(mddev->sync_thread); /* possibly kick off a reshape */
 
-	mddev->changed = 1;
+	bdev = bdget_disk(mddev->gendisk, 0);
+	if (bdev) {
+		bd_set_size(bdev, mddev->array_size << 1);
+		blkdev_ioctl(bdev->bd_inode, NULL, BLKRRPART, 0);
+		bdput(bdev);
+	}
+
 	md_new_event(mddev);
 	kobject_uevent(&mddev->gendisk->kobj, KOBJ_CHANGE);
 	return 0;
@@ -3453,7 +3460,6 @@ static int do_md_stop(mddev_t * mddev, i
 			mddev->pers = NULL;
 
 			set_capacity(disk, 0);
-			mddev->changed = 1;
 
 			if (mddev->ro)
 				mddev->ro = 0;
@@ -4593,20 +4599,6 @@ static int md_release(struct inode *inod
 	return 0;
 }
 
-static int md_media_changed(struct gendisk *disk)
-{
-	mddev_t *mddev = disk->private_data;
-
-	return mddev->changed;
-}
-
-static int md_revalidate(struct gendisk *disk)
-{
-	mddev_t *mddev = disk->private_data;
-
-	mddev->changed = 0;
-	return 0;
-}
 static struct block_device_operations md_fops =
 {
 	.owner		= THIS_MODULE,
@@ -4614,8 +4606,6 @@ static struct block_device_operations md
 	.release	= md_release,
 	.ioctl		= md_ioctl,
 	.getgeo		= md_getgeo,
-	.media_changed	= md_media_changed,
-	.revalidate_disk= md_revalidate,
 };
 
 static int md_thread(void * arg)

diff .prev/drivers/md/raid1.c ./drivers/md/raid1.c
--- .prev/drivers/md/raid1.c	2007-05-08 14:24:00.000000000 +1000
+++ ./drivers/md/raid1.c	2007-05-07 17:02:27.000000000 +1000
@@ -2063,7 +2063,6 @@ static int raid1_resize(mddev_t *mddev, 
 	 */
 	mddev->array_size = sectors>>1;
 	set_capacity(mddev->gendisk, mddev->array_size << 1);
-	mddev->changed = 1;
 	if (mddev->array_size > mddev->size && mddev->recovery_cp == MaxSector) {
 		mddev->recovery_cp = mddev->size << 1;
 		set_bit(MD_RECOVERY_NEEDED, &mddev->recovery);

diff .prev/drivers/md/raid5.c ./drivers/md/raid5.c
--- .prev/drivers/md/raid5.c	2007-05-08 14:24:00.000000000 +1000
+++ ./drivers/md/raid5.c	2007-05-07 17:03:05.000000000 +1000
@@ -4514,7 +4514,6 @@ static int raid5_resize(mddev_t *mddev, 
 	sectors &= ~((sector_t)mddev->chunk_size/512 - 1);
 	mddev->array_size = (sectors * (mddev->raid_disks-conf->max_degraded))>>1;
 	set_capacity(mddev->gendisk, mddev->array_size << 1);
-	mddev->changed = 1;
 	if (sectors/2  > mddev->size && mddev->recovery_cp == MaxSector) {
 		mddev->recovery_cp = mddev->size << 1;
 		set_bit(MD_RECOVERY_NEEDED, &mddev->recovery);
@@ -4649,7 +4648,6 @@ static void end_reshape(raid5_conf_t *co
 		conf->mddev->array_size = conf->mddev->size *
 			(conf->raid_disks - conf->max_degraded);
 		set_capacity(conf->mddev->gendisk, conf->mddev->array_size << 1);
-		conf->mddev->changed = 1;
 
 		bdev = bdget_disk(conf->mddev->gendisk, 0);
 		if (bdev) {

diff .prev/include/linux/raid/md_k.h ./include/linux/raid/md_k.h
--- .prev/include/linux/raid/md_k.h	2007-05-08 14:24:00.000000000 +1000
+++ ./include/linux/raid/md_k.h	2007-05-08 14:24:36.000000000 +1000
@@ -201,7 +201,6 @@ struct mddev_s
 	struct mutex			reconfig_mutex;
 	atomic_t			active;
 
-	int				changed;	/* true if we might need to reread partition info */
 	int				degraded;	/* whether md should consider
 							 * adding a spare
 							 */