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[Qemu-devel] [PATCH 2/6] qcow2: simplify qcow2_cache_put() and qcow2_cac


From: Alberto Garcia
Subject: [Qemu-devel] [PATCH 2/6] qcow2: simplify qcow2_cache_put() and qcow2_cache_entry_mark_dirty()
Date: Thu, 30 Apr 2015 13:11:41 +0300

Since all tables are now stored together, it is possible to obtain
the position of a particular table directly from its address, so the
operation becomes O(1).

Signed-off-by: Alberto Garcia <address@hidden>
---
 block/qcow2-cache.c | 22 +++++-----------------
 1 file changed, 5 insertions(+), 17 deletions(-)

diff --git a/block/qcow2-cache.c b/block/qcow2-cache.c
index 586880b..d3274f4 100644
--- a/block/qcow2-cache.c
+++ b/block/qcow2-cache.c
@@ -335,16 +335,12 @@ int qcow2_cache_get_empty(BlockDriverState *bs, 
Qcow2Cache *c, uint64_t offset,
 
 int qcow2_cache_put(BlockDriverState *bs, Qcow2Cache *c, void **table)
 {
-    int i;
+    int i = (*table - c->table_array) / c->table_size;
 
-    for (i = 0; i < c->size; i++) {
-        if (table_addr(c, i) == *table) {
-            goto found;
-        }
+    if (c->entries[i].offset == 0) {
+        return -ENOENT;
     }
-    return -ENOENT;
 
-found:
     c->entries[i].ref--;
     *table = NULL;
 
@@ -354,15 +350,7 @@ found:
 
 void qcow2_cache_entry_mark_dirty(Qcow2Cache *c, void *table)
 {
-    int i;
-
-    for (i = 0; i < c->size; i++) {
-        if (table_addr(c, i) == table) {
-            goto found;
-        }
-    }
-    abort();
-
-found:
+    int i = (table - c->table_array) / c->table_size;
+    assert(c->entries[i].offset != 0);
     c->entries[i].dirty = true;
 }
-- 
2.1.4




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