Add queue resizing support

Just get rid of the preallocated command map, use the slab cache
to get/free commands instead.

Original patch from FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>,
changed by me to not use a mempool.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

1 files changed, 32 insertions, 64 deletions

diff --git a/block/bsg.c b/block/bsg.c
index 9d77a0c72457..c56618ae54c3 100644
--- a/block/bsg.c
+++ b/block/bsg.c
@@ -33,8 +33,6 @@
 
 static char bsg_version[] = "block layer sg (bsg) 0.4";
 
-struct bsg_command;
-
 struct bsg_device {
         struct gendisk *disk;
         request_queue_t *queue;
@@ -46,8 +44,6 @@ struct bsg_device {
         int minor;
         int queued_cmds;
         int done_cmds;
-        unsigned long *cmd_bitmap;
-        struct bsg_command *cmd_map;
         wait_queue_head_t wq_done;
         wait_queue_head_t wq_free;
         char name[BDEVNAME_SIZE];
@@ -60,14 +56,7 @@ enum {
         BSG_F_WRITE_PERM        = 2,
 };
 
-/*
- * command allocation bitmap defines
- */
-#define BSG_CMDS_PAGE_ORDER     (1)
-#define BSG_CMDS_PER_LONG       (sizeof(unsigned long) * 8)
-#define BSG_CMDS_MASK           (BSG_CMDS_PER_LONG - 1)
-#define BSG_CMDS_BYTES          (PAGE_SIZE * (1 << BSG_CMDS_PAGE_ORDER))
-#define BSG_CMDS                (BSG_CMDS_BYTES / sizeof(struct bsg_command))
+#define BSG_DEFAULT_CMDS        64
 
 #undef BSG_DEBUG
 
@@ -94,6 +83,8 @@ static struct hlist_head bsg_device_list[BSG_LIST_SIZE];
 static struct class *bsg_class;
 static LIST_HEAD(bsg_class_list);
 
+static struct kmem_cache *bsg_cmd_cachep;
+
 /*
  * our internal command type
  */
@@ -111,14 +102,12 @@ struct bsg_command {
 static void bsg_free_command(struct bsg_command *bc)
 {
         struct bsg_device *bd = bc->bd;
-        unsigned long bitnr = bc - bd->cmd_map;
         unsigned long flags;
 
-        dprintk("%s: command bit offset %lu\n", bd->name, bitnr);
+        kmem_cache_free(bsg_cmd_cachep, bc);
 
         spin_lock_irqsave(&bd->lock, flags);
         bd->queued_cmds--;
-        __clear_bit(bitnr, bd->cmd_bitmap);
         spin_unlock_irqrestore(&bd->lock, flags);
 
         wake_up(&bd->wq_free);
@@ -127,32 +116,29 @@ static void bsg_free_command(struct bsg_command *bc)
 static struct bsg_command *__bsg_alloc_command(struct bsg_device *bd)
 {
         struct bsg_command *bc = NULL;
-        unsigned long *map;
-        int free_nr;
 
         spin_lock_irq(&bd->lock);
 
         if (bd->queued_cmds >= bd->max_queue)
                 goto out;
 
-        for (free_nr = 0, map = bd->cmd_bitmap; *map == ~0UL; map++)
-                free_nr += BSG_CMDS_PER_LONG;
-
-        BUG_ON(*map == ~0UL);
-
         bd->queued_cmds++;
-        free_nr += ffz(*map);
-        __set_bit(free_nr, bd->cmd_bitmap);
         spin_unlock_irq(&bd->lock);
 
-        bc = bd->cmd_map + free_nr;
+        bc = kmem_cache_alloc(bsg_cmd_cachep, GFP_USER);
+        if (unlikely(!bc)) {
+                spin_lock_irq(&bd->lock);
+                goto alloc_fail;
+        }
+
         memset(bc, 0, sizeof(*bc));
         bc->bd = bd;
         INIT_LIST_HEAD(&bc->list);
-        dprintk("%s: returning free cmd %p (bit %d)\n", bd->name, bc, free_nr);
+        dprintk("%s: returning free cmd %p\n", bd->name, bc);
         return bc;
+alloc_fail:
+        bd->queued_cmds--;
 out:
-        dprintk("%s: failed (depth %d)\n", bd->name, bd->queued_cmds);
         spin_unlock_irq(&bd->lock);
         return bc;
 }
@@ -356,8 +342,8 @@ static void bsg_rq_end_io(struct request *rq, int uptodate)
         struct bsg_device *bd = bc->bd;
         unsigned long flags;
 
-        dprintk("%s: finished rq %p bc %p, bio %p offset %Zd stat %d\n",
-                bd->name, rq, bc, bc->bio, bc - bd->cmd_map, uptodate);
+        dprintk("%s: finished rq %p bc %p, bio %p stat %d\n",
+                bd->name, rq, bc, bc->bio, uptodate);
 
         bc->hdr.duration = jiffies_to_msecs(jiffies - bc->hdr.duration);
 
@@ -703,21 +689,9 @@ bsg_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
         return bytes_read;
 }
 
-static void bsg_free_device(struct bsg_device *bd)
-{
-        if (bd->cmd_map)
-                free_pages((unsigned long) bd->cmd_map, BSG_CMDS_PAGE_ORDER);
-
-        kfree(bd->cmd_bitmap);
-        kfree(bd);
-}
-
 static struct bsg_device *bsg_alloc_device(void)
 {
-        struct bsg_command *cmd_map;
-        unsigned long *cmd_bitmap;
         struct bsg_device *bd;
-        int bits;
 
         bd = kzalloc(sizeof(struct bsg_device), GFP_KERNEL);
         if (unlikely(!bd))
@@ -725,19 +699,7 @@ static struct bsg_device *bsg_alloc_device(void)
 
         spin_lock_init(&bd->lock);
 
-        bd->max_queue = BSG_CMDS;
-
-        bits = (BSG_CMDS / BSG_CMDS_PER_LONG) + 1;
-        cmd_bitmap = kzalloc(bits * sizeof(unsigned long), GFP_KERNEL);
-        if (!cmd_bitmap)
-                goto out_free_bd;
-        bd->cmd_bitmap = cmd_bitmap;
-
-        cmd_map = (void *) __get_free_pages(GFP_KERNEL | __GFP_ZERO,
-                                                BSG_CMDS_PAGE_ORDER);
-        if (!cmd_map)
-                goto out_free_bitmap;
-        bd->cmd_map = cmd_map;
+        bd->max_queue = BSG_DEFAULT_CMDS;
 
         INIT_LIST_HEAD(&bd->busy_list);
         INIT_LIST_HEAD(&bd->done_list);
@@ -746,12 +708,6 @@ static struct bsg_device *bsg_alloc_device(void)
         init_waitqueue_head(&bd->wq_free);
         init_waitqueue_head(&bd->wq_done);
         return bd;
-
-out_free_bitmap:
-        kfree(cmd_bitmap);
-out_free_bd:
-        kfree(bd);
-        return NULL;
 }
 
 static int bsg_put_device(struct bsg_device *bd)
@@ -779,7 +735,7 @@ static int bsg_put_device(struct bsg_device *bd)
 
         blk_put_queue(bd->queue);
         hlist_del(&bd->dev_list);
-        bsg_free_device(bd);
+        kfree(bd);
 out:
         mutex_unlock(&bsg_mutex);
         return ret;
@@ -918,15 +874,17 @@ bsg_ioctl(struct inode *inode, struct file *file, unsigned int cmd,
                  */
         case SG_GET_COMMAND_Q:
                 return put_user(bd->max_queue, uarg);
-                case SG_SET_COMMAND_Q: {
+        case SG_SET_COMMAND_Q: {
                 int queue;
 
                 if (get_user(queue, uarg))
                         return -EFAULT;
-                if (queue > BSG_CMDS || queue < 1)
+                if (queue < 1)
                         return -EINVAL;
 
+                spin_lock_irq(&bd->lock);
                 bd->max_queue = queue;
+                spin_unlock_irq(&bd->lock);
                 return 0;
         }
 
@@ -1035,15 +993,25 @@ static int __init bsg_init(void)
 {
         int ret, i;
 
+        bsg_cmd_cachep = kmem_cache_create("bsg_cmd",
+                                sizeof(struct bsg_command), 0, 0, NULL, NULL);
+        if (!bsg_cmd_cachep) {
+                printk(KERN_ERR "bsg: failed creating slab cache\n");
+                return -ENOMEM;
+        }
+
         for (i = 0; i < BSG_LIST_SIZE; i++)
                 INIT_HLIST_HEAD(&bsg_device_list[i]);
 
         bsg_class = class_create(THIS_MODULE, "bsg");
-        if (IS_ERR(bsg_class))
+        if (IS_ERR(bsg_class)) {
+                kmem_cache_destroy(bsg_cmd_cachep);
                 return PTR_ERR(bsg_class);
+        }
 
         ret = register_chrdev(BSG_MAJOR, "bsg", &bsg_fops);
         if (ret) {
+                kmem_cache_destroy(bsg_cmd_cachep);
                 class_destroy(bsg_class);
                 return ret;
         }