Changeset 81a7858 in mainline for uspace/lib/ext4/libext4_extent.c

Timestamp:

2012-05-10T08:47:06Z (13 years ago)

Author:

Frantisek Princ <frantisek.princ@…>

Branches:

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

Children:

f2eece1

Parents:

bed78cb

Message:

more comments, now missing very small number of comments

File:

• uspace/lib/ext4/libext4_extent.c (modified) (10 diffs)

uspace/lib/ext4/libext4_extent.c

@@ -933 +933 @@
 }
 
-/** TODO comment
- *
+/** Append data block to the i-node.
+ *
+ * This function allocates data block, tries to append it
+ * to some existing extent or creates new extents.
+ * It includes possible extent tree modifications (splitting).
+ *
+ * @param inode_ref                     i-node to append block to
+ * @param iblock                        output logical number of newly allocated block
+ * @param fblock                        output physical block address of newly allocated block
+ * @return                                      error code
  */
 int ext4_extent_append_block(ext4_inode_ref_t *inode_ref,
@@ -968 +976 @@
         }
 
-        // Add new extent to the node
+        // Add new extent to the node if not present
         if (path_ptr->extent == NULL) {
                 goto append_extent;
@@ -979 +987 @@
         if (block_count < block_limit) {
 
+                // There is space for new block in the extent
+
                 if (block_count == 0) {
+
+                        // Existing extent is empty
 
                         rc = ext4_balloc_alloc_block(inode_ref, &phys_block);
@@ -986 +998 @@
                         }
 
+                        // Initialize extent
                         ext4_extent_set_first_block(path_ptr->extent, new_block_idx);
                         ext4_extent_set_start(path_ptr->extent, phys_block);
                         ext4_extent_set_block_count(path_ptr->extent, 1);
 
+                        // Update i-node
                         ext4_inode_set_size(inode_ref->inode, inode_size + block_size);
                         inode_ref->dirty = true;
@@ -998 +1012 @@
                 } else {
 
+                        // Existing extent contains some blocks
+
                         phys_block = ext4_extent_get_start(path_ptr->extent);
                         phys_block += ext4_extent_get_block_count(path_ptr->extent);
 
+                        // Check if the following block is free for allocation
                         bool free;
                         rc = ext4_balloc_try_alloc_block(inode_ref, phys_block, &free);
@@ -1008 +1025 @@
 
                         if (! free) {
-                                // target is not free
+                                // target is not free, new block must be appended to new extent
                                 goto append_extent;
                         }
 
 
+                        // Update extent
                         ext4_extent_set_block_count(path_ptr->extent, block_count + 1);
 
+                        // Update i-node
                         ext4_inode_set_size(inode_ref->inode, inode_size + block_size);
                         inode_ref->dirty = true;
@@ -1024 +1043 @@
         }
 
+// Append new extent to the tree
 append_extent:
 
         phys_block = 0;
-        // Allocate and insert insert new block
+
+        // Allocate new data block
         rc = ext4_balloc_alloc_block(inode_ref, &phys_block);
         if (rc != EOK) {
@@ -1034 +1055 @@
         }
 
+        // Append extent for new block (includes tree splitting if needed)
         rc = ext4_extent_append_extent(inode_ref, path, &path_ptr, new_block_idx);
         if (rc != EOK) {
@@ -1040 +1062 @@
         }
 
+        // Initialize newly created extent
         ext4_extent_set_block_count(path_ptr->extent, 1);
         ext4_extent_set_first_block(path_ptr->extent, new_block_idx);
         ext4_extent_set_start(path_ptr->extent, phys_block);
 
+        // Update i-node
         ext4_inode_set_size(inode_ref->inode, inode_size + block_size);
         inode_ref->dirty = true;
@@ -1049 +1073 @@
         path_ptr->block->dirty = true;
 
+
 finish:
-
+        // Set return values
         *iblock = new_block_idx;
         *fblock = phys_block;