[PATCH] md: tidy up raid5/6 hash table code

- replace open-coded hash chain with hlist macros

- Fix hash-table size at one page - it is already quite generous, so there
  will never be a need to use multiple pages, so no need for __get_free_pages

No functional change.

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

3 files changed, 33 insertions, 57 deletions

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 9fc50487e2ed..6e4db95cebb1 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -35,12 +35,10 @@
 #define STRIPE_SHIFT            (PAGE_SHIFT - 9)
 #define STRIPE_SECTORS          (STRIPE_SIZE>>9)
 #define IO_THRESHOLD            1
-#define HASH_PAGES              1
-#define HASH_PAGES_ORDER        0
-#define NR_HASH                 (HASH_PAGES * PAGE_SIZE / sizeof(struct stripe_head *))
+#define NR_HASH                 (PAGE_SIZE / sizeof(struct hlist_head))
 #define HASH_MASK               (NR_HASH - 1)
 
-#define stripe_hash(conf, sect) ((conf)->stripe_hashtbl[((sect) >> STRIPE_SHIFT) & HASH_MASK])
+#define stripe_hash(conf, sect) (&((conf)->stripe_hashtbl[((sect) >> STRIPE_SHIFT) & HASH_MASK]))
 
 /* bio's attached to a stripe+device for I/O are linked together in bi_sector
  * order without overlap.  There may be several bio's per stripe+device, and
@@ -113,29 +111,21 @@ static void release_stripe(struct stripe_head *sh)
         spin_unlock_irqrestore(&conf->device_lock, flags);
 }
 
-static void remove_hash(struct stripe_head *sh)
+static inline void remove_hash(struct stripe_head *sh)
 {
         PRINTK("remove_hash(), stripe %llu\n", (unsigned long long)sh->sector);
 
-        if (sh->hash_pprev) {
-                if (sh->hash_next)
-                        sh->hash_next->hash_pprev = sh->hash_pprev;
-                *sh->hash_pprev = sh->hash_next;
-                sh->hash_pprev = NULL;
-        }
+        hlist_del_init(&sh->hash);
 }
 
-static __inline__ void insert_hash(raid5_conf_t *conf, struct stripe_head *sh)
+static inline void insert_hash(raid5_conf_t *conf, struct stripe_head *sh)
 {
-        struct stripe_head **shp = &stripe_hash(conf, sh->sector);
+        struct hlist_head *hp = stripe_hash(conf, sh->sector);
 
         PRINTK("insert_hash(), stripe %llu\n", (unsigned long long)sh->sector);
 
         CHECK_DEVLOCK();
-        if ((sh->hash_next = *shp) != NULL)
-                (*shp)->hash_pprev = &sh->hash_next;
-        *shp = sh;
-        sh->hash_pprev = shp;
+        hlist_add_head(&sh->hash, hp);
 }
 
 
@@ -228,10 +218,11 @@ static inline void init_stripe(struct stripe_head *sh, sector_t sector, int pd_i
 static struct stripe_head *__find_stripe(raid5_conf_t *conf, sector_t sector)
 {
         struct stripe_head *sh;
+        struct hlist_node *hn;
 
         CHECK_DEVLOCK();
         PRINTK("__find_stripe, sector %llu\n", (unsigned long long)sector);
-        for (sh = stripe_hash(conf, sector); sh; sh = sh->hash_next)
+        hlist_for_each_entry(sh, hn, stripe_hash(conf, sector), hash)
                 if (sh->sector == sector)
                         return sh;
         PRINTK("__stripe %llu not in cache\n", (unsigned long long)sector);
@@ -1835,9 +1826,8 @@ static int run(mddev_t *mddev)
 
         conf->mddev = mddev;
 
-        if ((conf->stripe_hashtbl = (struct stripe_head **) __get_free_pages(GFP_ATOMIC, HASH_PAGES_ORDER)) == NULL)
+        if ((conf->stripe_hashtbl = kzalloc(PAGE_SIZE, GFP_KERNEL)) == NULL)
                 goto abort;
-        memset(conf->stripe_hashtbl, 0, HASH_PAGES * PAGE_SIZE);
 
         spin_lock_init(&conf->device_lock);
         init_waitqueue_head(&conf->wait_for_stripe);
@@ -1972,9 +1962,7 @@ static int run(mddev_t *mddev)
 abort:
         if (conf) {
                 print_raid5_conf(conf);
-                if (conf->stripe_hashtbl)
-                        free_pages((unsigned long) conf->stripe_hashtbl,
-                                                        HASH_PAGES_ORDER);
+                kfree(conf->stripe_hashtbl);
                 kfree(conf);
         }
         mddev->private = NULL;
@@ -1991,7 +1979,7 @@ static int stop(mddev_t *mddev)
         md_unregister_thread(mddev->thread);
         mddev->thread = NULL;
         shrink_stripes(conf);
-        free_pages((unsigned long) conf->stripe_hashtbl, HASH_PAGES_ORDER);
+        kfree(conf->stripe_hashtbl);
         blk_sync_queue(mddev->queue); /* the unplug fn references 'conf'*/
         sysfs_remove_group(&mddev->kobj, &raid5_attrs_group);
         kfree(conf);
@@ -2019,12 +2007,12 @@ static void print_sh (struct stripe_head *sh)
 static void printall (raid5_conf_t *conf)
 {
         struct stripe_head *sh;
+        struct hlist_node *hn;
         int i;
 
         spin_lock_irq(&conf->device_lock);
         for (i = 0; i < NR_HASH; i++) {
-                sh = conf->stripe_hashtbl[i];
-                for (; sh; sh = sh->hash_next) {
+                hlist_for_each_entry(sh, hn, &conf->stripe_hashtbl[i], hash) {
                         if (sh->raid_conf != conf)
                                 continue;
                         print_sh(sh);
diff --git a/drivers/md/raid6main.c b/drivers/md/raid6main.c
index 4062fc16ac2b..79b5244f44f4 100644
--- a/drivers/md/raid6main.c
+++ b/drivers/md/raid6main.c
@@ -40,12 +40,10 @@
 #define STRIPE_SHIFT            (PAGE_SHIFT - 9)
 #define STRIPE_SECTORS          (STRIPE_SIZE>>9)
 #define IO_THRESHOLD            1
-#define HASH_PAGES              1
-#define HASH_PAGES_ORDER        0
-#define NR_HASH                 (HASH_PAGES * PAGE_SIZE / sizeof(struct stripe_head *))
+#define NR_HASH                 (PAGE_SIZE / sizeof(struct hlist_head))
 #define HASH_MASK               (NR_HASH - 1)
 
-#define stripe_hash(conf, sect) ((conf)->stripe_hashtbl[((sect) >> STRIPE_SHIFT) & HASH_MASK])
+#define stripe_hash(conf, sect) (&((conf)->stripe_hashtbl[((sect) >> STRIPE_SHIFT) & HASH_MASK]))
 
 /* bio's attached to a stripe+device for I/O are linked together in bi_sector
  * order without overlap.  There may be several bio's per stripe+device, and
@@ -132,29 +130,21 @@ static void release_stripe(struct stripe_head *sh)
         spin_unlock_irqrestore(&conf->device_lock, flags);
 }
 
-static void remove_hash(struct stripe_head *sh)
+static inline void remove_hash(struct stripe_head *sh)
 {
         PRINTK("remove_hash(), stripe %llu\n", (unsigned long long)sh->sector);
 
-        if (sh->hash_pprev) {
-                if (sh->hash_next)
-                        sh->hash_next->hash_pprev = sh->hash_pprev;
-                *sh->hash_pprev = sh->hash_next;
-                sh->hash_pprev = NULL;
-        }
+        hlist_del_init(&sh->hash);
 }
 
-static __inline__ void insert_hash(raid6_conf_t *conf, struct stripe_head *sh)
+static inline void insert_hash(raid6_conf_t *conf, struct stripe_head *sh)
 {
-        struct stripe_head **shp = &stripe_hash(conf, sh->sector);
+        struct hlist_head *hp = stripe_hash(conf, sh->sector);
 
         PRINTK("insert_hash(), stripe %llu\n", (unsigned long long)sh->sector);
 
         CHECK_DEVLOCK();
-        if ((sh->hash_next = *shp) != NULL)
-                (*shp)->hash_pprev = &sh->hash_next;
-        *shp = sh;
-        sh->hash_pprev = shp;
+        hlist_add_head(&sh->hash, hp);
 }
 
 
@@ -247,10 +237,11 @@ static inline void init_stripe(struct stripe_head *sh, sector_t sector, int pd_i
 static struct stripe_head *__find_stripe(raid6_conf_t *conf, sector_t sector)
 {
         struct stripe_head *sh;
+        struct hlist_node *hn;
 
         CHECK_DEVLOCK();
         PRINTK("__find_stripe, sector %llu\n", (unsigned long long)sector);
-        for (sh = stripe_hash(conf, sector); sh; sh = sh->hash_next)
+        hlist_for_each_entry (sh, hn,  stripe_hash(conf, sector), hash)
                 if (sh->sector == sector)
                         return sh;
         PRINTK("__stripe %llu not in cache\n", (unsigned long long)sector);
@@ -1931,17 +1922,15 @@ static int run(mddev_t *mddev)
                 return -EIO;
         }
 
-        mddev->private = kmalloc (sizeof (raid6_conf_t)
-                                  + mddev->raid_disks * sizeof(struct disk_info),
-                                  GFP_KERNEL);
+        mddev->private = kzalloc(sizeof (raid6_conf_t)
+                                 + mddev->raid_disks * sizeof(struct disk_info),
+                                 GFP_KERNEL);
         if ((conf = mddev->private) == NULL)
                 goto abort;
-        memset (conf, 0, sizeof (*conf) + mddev->raid_disks * sizeof(struct disk_info) );
         conf->mddev = mddev;
 
-        if ((conf->stripe_hashtbl = (struct stripe_head **) __get_free_pages(GFP_ATOMIC, HASH_PAGES_ORDER)) == NULL)
+        if ((conf->stripe_hashtbl = kzalloc(PAGE_SIZE, GFP_KERNEL)) == NULL)
                 goto abort;
-        memset(conf->stripe_hashtbl, 0, HASH_PAGES * PAGE_SIZE);
 
         conf->spare_page = alloc_page(GFP_KERNEL);
         if (!conf->spare_page)
@@ -2085,9 +2074,7 @@ abort:
                 print_raid6_conf(conf);
                 if (conf->spare_page)
                         put_page(conf->spare_page);
-                if (conf->stripe_hashtbl)
-                        free_pages((unsigned long) conf->stripe_hashtbl,
-                                                        HASH_PAGES_ORDER);
+                kfree(conf->stripe_hashtbl);
                 kfree(conf);
         }
         mddev->private = NULL;
@@ -2104,7 +2091,7 @@ static int stop (mddev_t *mddev)
         md_unregister_thread(mddev->thread);
         mddev->thread = NULL;
         shrink_stripes(conf);
-        free_pages((unsigned long) conf->stripe_hashtbl, HASH_PAGES_ORDER);
+        kfree(conf->stripe_hashtbl);
         blk_sync_queue(mddev->queue); /* the unplug fn references 'conf'*/
         kfree(conf);
         mddev->private = NULL;
@@ -2131,12 +2118,13 @@ static void print_sh (struct seq_file *seq, struct stripe_head *sh)
 static void printall (struct seq_file *seq, raid6_conf_t *conf)
 {
         struct stripe_head *sh;
+        struct hlist_node *hn;
         int i;
 
         spin_lock_irq(&conf->device_lock);
         for (i = 0; i < NR_HASH; i++) {
                 sh = conf->stripe_hashtbl[i];
-                for (; sh; sh = sh->hash_next) {
+                hlist_for_each_entry(sh, hn, &conf->stripe_hashtbl[i], hash) {
                         if (sh->raid_conf != conf)
                                 continue;
                         print_sh(seq, sh);
diff --git a/include/linux/raid/raid5.h b/include/linux/raid/raid5.h
index 28fcd7533ac4..394da8207b34 100644
--- a/include/linux/raid/raid5.h
+++ b/include/linux/raid/raid5.h
@@ -126,7 +126,7 @@
  */
 
 struct stripe_head {
-        struct stripe_head      *hash_next, **hash_pprev; /* hash pointers */
+        struct hlist_node       hash;
         struct list_head        lru;                    /* inactive_list or handle_list */
         struct raid5_private_data       *raid_conf;
         sector_t                sector;                 /* sector of this row */
@@ -204,7 +204,7 @@ struct disk_info {
 };
 
 struct raid5_private_data {
-        struct stripe_head      **stripe_hashtbl;
+        struct hlist_head       *stripe_hashtbl;
         mddev_t                 *mddev;
         struct disk_info        *spare;
         int                     chunk_size, level, algorithm;