dma-debug: add dma_debug_resize_entries() to adjust the number of dma_debug_entries

We use a static value for the number of dma_debug_entries. It can be
overwritten by a kernel command line option.

Some IOMMUs (e.g. GART) can't set an appropriate value by a kernel
command line option because they can't know such value until they
finish initializing up their hardware.

This patch adds dma_debug_resize_entries() enables IOMMUs to adjust
the number of dma_debug_entries anytime.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Acked-by: Joerg Roedel <joerg.roedel@amd.com>
Cc: fujita.tomonori@lab.ntt.co.jp
Cc: akpm@linux-foundation.org
LKML-Reference: <20090415182234R.fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

2 files changed, 73 insertions, 6 deletions

diff --git a/include/linux/dma-debug.h b/include/linux/dma-debug.h
index 28d53cb7b5a2..171ad8aedc83 100644
--- a/include/linux/dma-debug.h
+++ b/include/linux/dma-debug.h
@@ -32,6 +32,8 @@ extern void dma_debug_add_bus(struct bus_type *bus);
 
 extern void dma_debug_init(u32 num_entries);
 
+extern int dma_debug_resize_entries(u32 num_entries);
+
 extern void debug_dma_map_page(struct device *dev, struct page *page,
                                size_t offset, size_t size,
                                int direction, dma_addr_t dma_addr,
@@ -91,6 +93,11 @@ static inline void dma_debug_init(u32 num_entries)
 {
 }
 
+static inline int dma_debug_resize_entries(u32 num_entries)
+{
+        return 0;
+}
+
 static inline void debug_dma_map_page(struct device *dev, struct page *page,
                                       size_t offset, size_t size,
                                       int direction, dma_addr_t dma_addr,
diff --git a/lib/dma-debug.c b/lib/dma-debug.c
index d3da7edc034f..5d61019330cd 100644
--- a/lib/dma-debug.c
+++ b/lib/dma-debug.c
@@ -85,6 +85,7 @@ static u32 show_num_errors = 1;
 
 static u32 num_free_entries;
 static u32 min_free_entries;
+static u32 nr_total_entries;
 
 /* number of preallocated entries requested by kernel cmdline */
 static u32 req_entries;
@@ -257,6 +258,21 @@ static void add_dma_entry(struct dma_debug_entry *entry)
         put_hash_bucket(bucket, &flags);
 }
 
+static struct dma_debug_entry *__dma_entry_alloc(void)
+{
+        struct dma_debug_entry *entry;
+
+        entry = list_entry(free_entries.next, struct dma_debug_entry, list);
+        list_del(&entry->list);
+        memset(entry, 0, sizeof(*entry));
+
+        num_free_entries -= 1;
+        if (num_free_entries < min_free_entries)
+                min_free_entries = num_free_entries;
+
+        return entry;
+}
+
 /* struct dma_entry allocator
  *
  * The next two functions implement the allocator for
@@ -276,9 +292,7 @@ static struct dma_debug_entry *dma_entry_alloc(void)
                 goto out;
         }
 
-        entry = list_entry(free_entries.next, struct dma_debug_entry, list);
-        list_del(&entry->list);
-        memset(entry, 0, sizeof(*entry));
+        entry = __dma_entry_alloc();
 
 #ifdef CONFIG_STACKTRACE
         entry->stacktrace.max_entries = DMA_DEBUG_STACKTRACE_ENTRIES;
@@ -286,9 +300,6 @@ static struct dma_debug_entry *dma_entry_alloc(void)
         entry->stacktrace.skip = 2;
         save_stack_trace(&entry->stacktrace);
 #endif
-        num_free_entries -= 1;
-        if (num_free_entries < min_free_entries)
-                min_free_entries = num_free_entries;
 
 out:
         spin_unlock_irqrestore(&free_entries_lock, flags);
@@ -310,6 +321,53 @@ static void dma_entry_free(struct dma_debug_entry *entry)
         spin_unlock_irqrestore(&free_entries_lock, flags);
 }
 
+int dma_debug_resize_entries(u32 num_entries)
+{
+        int i, delta, ret = 0;
+        unsigned long flags;
+        struct dma_debug_entry *entry;
+        LIST_HEAD(tmp);
+
+        spin_lock_irqsave(&free_entries_lock, flags);
+
+        if (nr_total_entries < num_entries) {
+                delta = num_entries - nr_total_entries;
+
+                spin_unlock_irqrestore(&free_entries_lock, flags);
+
+                for (i = 0; i < delta; i++) {
+                        entry = kzalloc(sizeof(*entry), GFP_KERNEL);
+                        if (!entry)
+                                break;
+
+                        list_add_tail(&entry->list, &tmp);
+                }
+
+                spin_lock_irqsave(&free_entries_lock, flags);
+
+                list_splice(&tmp, &free_entries);
+                nr_total_entries += i;
+                num_free_entries += i;
+        } else {
+                delta = nr_total_entries - num_entries;
+
+                for (i = 0; i < delta && !list_empty(&free_entries); i++) {
+                        entry = __dma_entry_alloc();
+                        kfree(entry);
+                }
+
+                nr_total_entries -= i;
+        }
+
+        if (nr_total_entries != num_entries)
+                ret = 1;
+
+        spin_unlock_irqrestore(&free_entries_lock, flags);
+
+        return ret;
+}
+EXPORT_SYMBOL(dma_debug_resize_entries);
+
 /*
  * DMA-API debugging init code
  *
@@ -490,6 +548,8 @@ void dma_debug_init(u32 num_entries)
                 return;
         }
 
+        nr_total_entries = num_free_entries;
+
         printk(KERN_INFO "DMA-API: debugging enabled by kernel config\n");
 }