Changeset 377cce8 in mainline

Timestamp:

2010-07-25T21:08:47Z (14 years ago)

Author:

Jakub Jermar <jakub@…>

Branches:

lfn, master, serial, ticket/834-toolchain-update, topic/msim-upgrade, topic/simplify-dev-export

Children:

746f623

Parents:

c621f4aa

Message:

Start to cache the FAT node's last cluster in fat_node_t and change
fat_append/chop_clusters() to make use of the cached value.

Location:

uspace/srv/fs/fat

Files:

• fat.h (modified) (1 diff)
• fat_fat.c (modified) (6 diffs)
• fat_fat.h (modified) (1 diff)
• fat_ops.c (modified) (3 diffs)

uspace/srv/fs/fat/fat.h

@@ -198 +198 @@
         unsigned                refcnt;
         bool                    dirty;
+
+        /*
+         * Cache of the node's last cluster to avoid some unnecessary FAT walks.
+         */
+        bool                    lastc_cached_valid;
+        fat_cluster_t           lastc_cached_value;
 } fat_node_t;
 

uspace/srv/fs/fat/fat_fat.c

@@ -511 +511 @@
  * @param nodep         Node representing the file.
  * @param mcl           First cluster of the cluster chain to append.
+ * @param lcl           Last cluster of the cluster chain to append.
  *
  * @return              EOK on success or a negative error code.
  */
-int fat_append_clusters(fat_bs_t *bs, fat_node_t *nodep, fat_cluster_t mcl)
+int
+fat_append_clusters(fat_bs_t *bs, fat_node_t *nodep, fat_cluster_t mcl,
+    fat_cluster_t lcl)
 {
         dev_handle_t dev_handle = nodep->idx->dev_handle;
-        fat_cluster_t lcl;
+        fat_cluster_t lastc;
         uint16_t numc;
         uint8_t fatno;
         int rc;
 
-        rc = fat_cluster_walk(bs, dev_handle, nodep->firstc, &lcl, &numc,
-            (uint16_t) -1);
-        if (rc != EOK)
-                return rc;
-
-        if (numc == 0) {
-                /* No clusters allocated to the node yet. */
-                nodep->firstc = mcl;
-                nodep->dirty = true;            /* need to sync node */
-                return EOK;
+        if (nodep->lastc_cached_valid) {
+                lastc = nodep->lastc_cached_value;
+                nodep->lastc_cached_valid = false;
+        } else {
+                rc = fat_cluster_walk(bs, dev_handle, nodep->firstc, &lastc,
+                    &numc, (uint16_t) -1);
+                if (rc != EOK)
+                        return rc;
+
+                if (numc == 0) {
+                        /* No clusters allocated to the node yet. */
+                        nodep->firstc = mcl;
+                        nodep->dirty = true;    /* need to sync node */
+                        return EOK;
+                }
         }
 
         for (fatno = FAT1; fatno < bs->fatcnt; fatno++) {
-                rc = fat_set_cluster(bs, nodep->idx->dev_handle, fatno, lcl,
+                rc = fat_set_cluster(bs, nodep->idx->dev_handle, fatno, lastc,
                     mcl);
                 if (rc != EOK)
                         return rc;
         }
+
+        nodep->lastc_cached_valid = true;
+        nodep->lastc_cached_value = lcl;
 
         return EOK;
@@ -548 +559 @@
  * @param bs            Buffer holding the boot sector of the file system.
  * @param nodep         FAT node where the chopping will take place.
- * @param lastc         Last cluster which will remain in the node. If this
+ * @param lcl           Last cluster which will remain in the node. If this
  *                      argument is FAT_CLST_RES0, then all clusters will
  *                      be chopped off.
@@ -554 +565 @@
  * @return              EOK on success or a negative return code.
  */
-int fat_chop_clusters(fat_bs_t *bs, fat_node_t *nodep, fat_cluster_t lastc)
-{
-        int rc;
-
+int fat_chop_clusters(fat_bs_t *bs, fat_node_t *nodep, fat_cluster_t lcl)
+{
+        int rc;
         dev_handle_t dev_handle = nodep->idx->dev_handle;
-        if (lastc == FAT_CLST_RES0) {
+
+        nodep->lastc_cached_valid = false;
+        if (lcl == FAT_CLST_RES0) {
                 /* The node will have zero size and no clusters allocated. */
                 rc = fat_free_clusters(bs, dev_handle, nodep->firstc);
@@ -570 +582 @@
                 unsigned fatno;
 
-                rc = fat_get_cluster(bs, dev_handle, FAT1, lastc, &nextc);
+                rc = fat_get_cluster(bs, dev_handle, FAT1, lcl, &nextc);
                 if (rc != EOK)
                         return rc;
@@ -576 +588 @@
                 /* Terminate the cluster chain in all copies of FAT. */
                 for (fatno = FAT1; fatno < bs->fatcnt; fatno++) {
-                        rc = fat_set_cluster(bs, dev_handle, fatno, lastc,
+                        rc = fat_set_cluster(bs, dev_handle, fatno, lcl,
                             FAT_CLST_LAST1);
                         if (rc != EOK)
@@ -587 +599 @@
                         return rc;
         }
+
+        nodep->lastc_cached_valid = true;
+        nodep->lastc_cached_value = lcl;
 
         return EOK;

uspace/srv/fs/fat/fat_fat.h

@@ -72 +72 @@
 
 extern int fat_append_clusters(struct fat_bs *, struct fat_node *,
-    fat_cluster_t);
+    fat_cluster_t, fat_cluster_t);
 extern int fat_chop_clusters(struct fat_bs *, struct fat_node *,
     fat_cluster_t);

uspace/srv/fs/fat/fat_ops.c

@@ -101 +101 @@
         node->refcnt = 0;
         node->dirty = false;
+        node->lastc_cached_valid = false;
+        node->lastc_cached_value = FAT_CLST_LAST1;
 }
 
@@ -691 +693 @@
                 return rc;
         }
-        rc = fat_append_clusters(bs, parentp, mcl);
+        rc = fat_append_clusters(bs, parentp, mcl, lcl);
         if (rc != EOK) {
                 (void) fat_free_clusters(bs, parentp->idx->dev_handle, mcl);
@@ -1438 +1440 @@
                  * node's cluster chain.
                  */
-                rc = fat_append_clusters(bs, nodep, mcl);
+                rc = fat_append_clusters(bs, nodep, mcl, lcl);
                 if (rc != EOK) {
                         (void) fat_free_clusters(bs, dev_handle, mcl);