[PATCH] md: remove personality numbering from md

md supports multiple different RAID level, each being implemented by a
'personality' (which is often in a separate module).

These personalities have fairly artificial 'numbers'.  The numbers
are use to:
 1- provide an index into an array where the various personalities
    are recorded
 2- identify the module (via an alias) which implements are particular
    personality.

Neither of these uses really justify the existence of personality numbers.
The array can be replaced by a linked list which is searched (array lookup
only happens very rarely).  Module identification can be done using an alias
based on level rather than 'personality' number.

The current 'raid5' modules support two level (4 and 5) but only one
personality.  This slight awkwardness (which was handled in the mapping from
level to personality) can be better handled by allowing raid5 to register 2
personalities.

With this change in place, the core md module does not need to have an
exhaustive list of all possible personalities, so other personalities can be
added independently.

This patch also moves the check for chunksize being non-zero into the ->run
routines for the personalities that need it, rather than having it in core-md.
 This has a side effect of allowing 'faulty' and 'linear' not to have a
chunk-size set.

Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 29 insertions, 50 deletions

diff --git a/drivers/md/md.c b/drivers/md/md.c
index a6a066fc92e3..07f180f95b47 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -68,7 +68,7 @@
 static void autostart_arrays (int part);
 #endif
 
-static mdk_personality_t *pers[MAX_PERSONALITY];
+static LIST_HEAD(pers_list);
 static DEFINE_SPINLOCK(pers_lock);
 
 /*
@@ -303,6 +303,15 @@ static mdk_rdev_t * find_rdev(mddev_t * mddev, dev_t dev)
         return NULL;
 }
 
+static struct mdk_personality *find_pers(int level)
+{
+        struct mdk_personality *pers;
+        list_for_each_entry(pers, &pers_list, list)
+                if (pers->level == level)
+                        return pers;
+        return NULL;
+}
+
 static inline sector_t calc_dev_sboffset(struct block_device *bdev)
 {
         sector_t size = bdev->bd_inode->i_size >> BLOCK_SIZE_BITS;
@@ -1744,7 +1753,7 @@ static void analyze_sbs(mddev_t * mddev)
 static ssize_t
 level_show(mddev_t *mddev, char *page)
 {
-        mdk_personality_t *p = mddev->pers;
+        struct mdk_personality *p = mddev->pers;
         if (p == NULL && mddev->raid_disks == 0)
                 return 0;
         if (mddev->level >= 0)
@@ -1960,11 +1969,12 @@ static int start_dirty_degraded;
 
 static int do_md_run(mddev_t * mddev)
 {
-        int pnum, err;
+        int err;
         int chunk_size;
         struct list_head *tmp;
         mdk_rdev_t *rdev;
         struct gendisk *disk;
+        struct mdk_personality *pers;
         char b[BDEVNAME_SIZE];
 
         if (list_empty(&mddev->disks))
@@ -1981,20 +1991,8 @@ static int do_md_run(mddev_t * mddev)
                 analyze_sbs(mddev);
 
         chunk_size = mddev->chunk_size;
-        pnum = level_to_pers(mddev->level);
 
-        if ((pnum != MULTIPATH) && (pnum != RAID1)) {
-                if (!chunk_size) {
-                        /*
-                         * 'default chunksize' in the old md code used to
-                         * be PAGE_SIZE, baaad.
-                         * we abort here to be on the safe side. We don't
-                         * want to continue the bad practice.
-                         */
-                        printk(KERN_ERR 
-                                "no chunksize specified, see 'man raidtab'\n");
-                        return -EINVAL;
-                }
+        if (chunk_size) {
                 if (chunk_size > MAX_CHUNK_SIZE) {
                         printk(KERN_ERR "too big chunk_size: %d > %d\n",
                                 chunk_size, MAX_CHUNK_SIZE);
@@ -2030,10 +2028,7 @@ static int do_md_run(mddev_t * mddev)
         }
 
 #ifdef CONFIG_KMOD
-        if (!pers[pnum])
-        {
-                request_module("md-personality-%d", pnum);
-        }
+        request_module("md-level-%d", mddev->level);
 #endif
 
         /*
@@ -2055,14 +2050,14 @@ static int do_md_run(mddev_t * mddev)
                 return -ENOMEM;
 
         spin_lock(&pers_lock);
-        if (!pers[pnum] || !try_module_get(pers[pnum]->owner)) {
+        pers = find_pers(mddev->level);
+        if (!pers || !try_module_get(pers->owner)) {
                 spin_unlock(&pers_lock);
-                printk(KERN_WARNING "md: personality %d is not loaded!\n",
-                       pnum);
+                printk(KERN_WARNING "md: personality for level %d is not loaded!\n",
+                       mddev->level);
                 return -EINVAL;
         }
-
-        mddev->pers = pers[pnum];
+        mddev->pers = pers;
         spin_unlock(&pers_lock);
 
         mddev->recovery = 0;
@@ -3701,15 +3696,14 @@ static int md_seq_show(struct seq_file *seq, void *v)
         struct list_head *tmp2;
         mdk_rdev_t *rdev;
         struct mdstat_info *mi = seq->private;
-        int i;
         struct bitmap *bitmap;
 
         if (v == (void*)1) {
+                struct mdk_personality *pers;
                 seq_printf(seq, "Personalities : ");
                 spin_lock(&pers_lock);
-                for (i = 0; i < MAX_PERSONALITY; i++)
-                        if (pers[i])
-                                seq_printf(seq, "[%s] ", pers[i]->name);
+                list_for_each_entry(pers, &pers_list, list)
+                        seq_printf(seq, "[%s] ", pers->name);
 
                 spin_unlock(&pers_lock);
                 seq_printf(seq, "\n");
@@ -3870,35 +3864,20 @@ static struct file_operations md_seq_fops = {
         .poll           = mdstat_poll,
 };
 
-int register_md_personality(int pnum, mdk_personality_t *p)
+int register_md_personality(struct mdk_personality *p)
 {
-        if (pnum >= MAX_PERSONALITY) {
-                printk(KERN_ERR
-                       "md: tried to install personality %s as nr %d, but max is %lu\n",
-                       p->name, pnum, MAX_PERSONALITY-1);
-                return -EINVAL;
-        }
-
         spin_lock(&pers_lock);
-        if (pers[pnum]) {
-                spin_unlock(&pers_lock);
-                return -EBUSY;
-        }
-
-        pers[pnum] = p;
-        printk(KERN_INFO "md: %s personality registered as nr %d\n", p->name, pnum);
+        list_add_tail(&p->list, &pers_list);
+        printk(KERN_INFO "md: %s personality registered for level %d\n", p->name, p->level);
         spin_unlock(&pers_lock);
         return 0;
 }
 
-int unregister_md_personality(int pnum)
+int unregister_md_personality(struct mdk_personality *p)
 {
-        if (pnum >= MAX_PERSONALITY)
-                return -EINVAL;
-
-        printk(KERN_INFO "md: %s personality unregistered\n", pers[pnum]->name);
+        printk(KERN_INFO "md: %s personality unregistered\n", p->name);
         spin_lock(&pers_lock);
-        pers[pnum] = NULL;
+        list_del_init(&p->list);
         spin_unlock(&pers_lock);
         return 0;
 }