block/mirror: limit qiov to IOV_MAX elements

[qemu.git] / page_cache.c

diff --git a/page_cache.c b/page_cache.c
index 809dadc7ebf4f6c65d925975569168d84c9a0cc4..cf8878d1d7393f4587342cffd16596b93ec1e0c2 100644 (file)
--- a/page_cache.c
+++ b/page_cache.c
@@ -21,7 +21,6 @@
 #include <sys/types.h>
 #include <stdbool.h>
 #include <glib.h>
-#include <strings.h>
 
 #include "qemu-common.h"
 #include "migration/page_cache.h"
@@ -34,6 +33,9 @@
     do { } while (0)
 #endif
 
+/* the page in cache will not be replaced in two cycles */
+#define CACHED_PAGE_LIFETIME 2
+
 typedef struct CacheItem CacheItem;
 
 struct CacheItem {
@@ -61,8 +63,12 @@ PageCache *cache_init(int64_t num_pages, unsigned int page_size)
         return NULL;
     }
 
-    cache = g_malloc(sizeof(*cache));
-
+    /* We prefer not to abort if there is no memory */
+    cache = g_try_malloc(sizeof(*cache));
+    if (!cache) {
+        DPRINTF("Failed to allocate cache\n");
+        return NULL;
+    }
     /* round down to the nearest power of 2 */
     if (!is_power_of_2(num_pages)) {
         num_pages = pow2floor(num_pages);
@@ -75,8 +81,14 @@ PageCache *cache_init(int64_t num_pages, unsigned int page_size)
 
     DPRINTF("Setting cache buckets to %" PRId64 "\n", cache->max_num_items);
 
-    cache->page_cache = g_malloc((cache->max_num_items) *
-                                 sizeof(*cache->page_cache));
+    /* We prefer not to abort if there is no memory */
+    cache->page_cache = g_try_malloc((cache->max_num_items) *
+                                     sizeof(*cache->page_cache));
+    if (!cache->page_cache) {
+        DPRINTF("Failed to allocate cache->page_cache\n");
+        g_free(cache);
+        return NULL;
+    }
 
     for (i = 0; i < cache->max_num_items; i++) {
         cache->page_cache[i].it_data = NULL;
@@ -100,6 +112,7 @@ void cache_fini(PageCache *cache)
 
     g_free(cache->page_cache);
     cache->page_cache = NULL;
+    g_free(cache);
 }
 
 static size_t cache_get_cache_pos(const PageCache *cache,
@@ -112,18 +125,6 @@ static size_t cache_get_cache_pos(const PageCache *cache,
     return pos;
 }
 
-bool cache_is_cached(const PageCache *cache, uint64_t addr)
-{
-    size_t pos;
-
-    g_assert(cache);
-    g_assert(cache->page_cache);
-
-    pos = cache_get_cache_pos(cache, addr);
-
-    return (cache->page_cache[pos].it_addr == addr);
-}
-
 static CacheItem *cache_get_by_addr(const PageCache *cache, uint64_t addr)
 {
     size_t pos;
@@ -141,27 +142,51 @@ uint8_t *get_cached_data(const PageCache *cache, uint64_t addr)
     return cache_get_by_addr(cache, addr)->it_data;
 }
 
-void cache_insert(PageCache *cache, uint64_t addr, uint8_t *pdata)
+bool cache_is_cached(const PageCache *cache, uint64_t addr,
+                     uint64_t current_age)
 {
+    CacheItem *it;
 
-    CacheItem *it = NULL;
+    it = cache_get_by_addr(cache, addr);
 
-    g_assert(cache);
-    g_assert(cache->page_cache);
+    if (it->it_addr == addr) {
+        /* update the it_age when the cache hit */
+        it->it_age = current_age;
+        return true;
+    }
+    return false;
+}
+
+int cache_insert(PageCache *cache, uint64_t addr, const uint8_t *pdata,
+                 uint64_t current_age)
+{
+
+    CacheItem *it;
 
     /* actual update of entry */
     it = cache_get_by_addr(cache, addr);
 
-    /* free old cached data if any */
-    g_free(it->it_data);
-
+    if (it->it_data && it->it_addr != addr &&
+        it->it_age + CACHED_PAGE_LIFETIME > current_age) {
+        /* the cache page is fresh, don't replace it */
+        return -1;
+    }
+    /* allocate page */
     if (!it->it_data) {
+        it->it_data = g_try_malloc(cache->page_size);
+        if (!it->it_data) {
+            DPRINTF("Error allocating page\n");
+            return -1;
+        }
         cache->num_items++;
     }
 
-    it->it_data = pdata;
-    it->it_age = ++cache->max_item_age;
+    memcpy(it->it_data, pdata, cache->page_size);
+
+    it->it_age = current_age;
     it->it_addr = addr;
+
+    return 0;
 }
 
 int64_t cache_resize(PageCache *cache, int64_t new_num_pages)