Changeset ee3b6150 in mainline for uspace/lib/ext4/libext4_ialloc.c

Timestamp:

2012-04-23T16:01:14Z (13 years ago)

Author:

Frantisek Princ <frantisek.princ@…>

Branches:

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

Children:

bc03679

Parents:

6773ff3

Message:

I-node allocator comments, hash comments, part of the extent comments

File:

• uspace/lib/ext4/libext4_ialloc.c (modified) (21 diffs)

uspace/lib/ext4/libext4_ialloc.c

@@ -40 +40 @@
 #include "libext4.h"
 
+
+/** Convert i-node number to relative index in block group.
+ *
+ * @param sb    superblock
+ * @param inode i-node number to be converted
+ * @return              index of the i-node in the block group
+ */
 static uint32_t ext4_ialloc_inode2index_in_group(ext4_superblock_t *sb,
                 uint32_t inode)
@@ -47 +54 @@
 }
 
+/** Convert relative index of i-node to absolute i-node number.
+ *
+ * @param sb    superblock
+ * @param inode index to be converted
+ * @return              absolute number of the i-node
+ */
 static uint32_t ext4_ialloc_index_in_group2inode(ext4_superblock_t *sb,
                 uint32_t index, uint32_t bgid)
@@ -54 +67 @@
 }
 
+/** Compute block group number from the i-node number.
+ *
+ * @param sb            superblock
+ * @param inode         i-node number to be found the block group for
+ * @return                      block group number computed from i-node number
+ */
 static uint32_t ext4_ialloc_get_bgid_of_inode(ext4_superblock_t *sb,
                 uint32_t inode)
@@ -63 +82 @@
 
 
+/** Free i-node number and modify filesystem data structers.
+ *
+ * @param fs            filesystem, where the i-node is located
+ * @param index         index of i-node to be release
+ * @param is_dir        flag us for information whether i-node is directory or not
+ */
 int ext4_ialloc_free_inode(ext4_filesystem_t *fs, uint32_t index, bool is_dir)
 {
@@ -69 +94 @@
         ext4_superblock_t *sb = fs->superblock;
 
+        // Compute index of block group and load it
         uint32_t block_group = ext4_ialloc_get_bgid_of_inode(sb, index);
 
@@ -77 +103 @@
         }
 
+        // Load i-node bitmap
         uint32_t bitmap_block_addr = ext4_block_group_get_inode_bitmap(
                         bg_ref->block_group, sb);
@@ -85 +112 @@
         }
 
+        // Free i-node in the bitmap
         uint32_t index_in_group = ext4_ialloc_inode2index_in_group(sb, index);
         ext4_bitmap_free_bit(bitmap_block->data, index_in_group);
         bitmap_block->dirty = true;
 
+        // Put back the block with bitmap
         rc = block_put(bitmap_block);
         if (rc != EOK) {
@@ -96 +125 @@
         }
 
-        // if inode is directory, decrement used directories count
+        // If released i-node is a directory, decrement used directories count
         if (is_dir) {
                 uint32_t bg_used_dirs = ext4_block_group_get_used_dirs_count(
@@ -112 +141 @@
                         sb, free_inodes);
 
+        // Set unused i-nodes count if supported
         if (ext4_block_group_has_flag(bg_ref->block_group, EXT4_BLOCK_GROUP_INODE_UNINIT)) {
                 uint32_t unused_inodes = ext4_block_group_get_itable_unused(
@@ -121 +151 @@
         bg_ref->dirty = true;
 
+        // Put back the modified block group
         rc = ext4_filesystem_put_block_group_ref(bg_ref);
         if (rc != EOK) {
@@ -134 +165 @@
 }
 
+/** I-node allocation algorithm.
+ *
+ * This is more simple algorithm, than Orlov allocator used in the Linux kernel
+ *
+ * @param fs            filesystem to allocate i-node on
+ * @param index         output value - allocated i-node number
+ * @param is_dir        flag if allocated i-node will be file or directory
+ * @return                      error code
+ */
 int ext4_ialloc_alloc_inode(ext4_filesystem_t *fs, uint32_t *index, bool is_dir)
 {
@@ -145 +185 @@
         uint32_t avg_free_inodes = sb_free_inodes / bg_count;
 
+        // Try to find free i-node in all block groups
         while (bgid < bg_count) {
 
+                // Load block group to check
                 ext4_block_group_ref_t *bg_ref;
                 rc = ext4_filesystem_get_block_group_ref(fs, bgid, &bg_ref);
@@ -152 +194 @@
                         return rc;
                 }
+
                 ext4_block_group_t *bg = bg_ref->block_group;
 
+                // Read necessary values for algorithm
                 uint32_t free_blocks = ext4_block_group_get_free_blocks_count(bg, sb);
                 uint32_t free_inodes = ext4_block_group_get_free_inodes_count(bg, sb);
                 uint32_t used_dirs = ext4_block_group_get_used_dirs_count(bg, sb);
 
+                // Check if this block group is good candidate for allocation
                 if ((free_inodes >= avg_free_inodes) && (free_blocks > 0)) {
 
+                        // Load block with bitmap
                         uint32_t bitmap_block_addr =  ext4_block_group_get_inode_bitmap(
                                         bg_ref->block_group, sb);
@@ -170 +216 @@
                         }
 
-                        // Alloc bit
+                        // Try to allocate i-node in the bitmap
                         uint32_t inodes_in_group = ext4_superblock_get_inodes_in_group(sb, bgid);
                         uint32_t index_in_group;
@@ -176 +222 @@
                                         bitmap_block->data, 0, &index_in_group, inodes_in_group);
 
-                        // Block group is full (inodes)
+                        // Block group has not any free i-node
                         if (rc == ENOSPC) {
                                 block_put(bitmap_block);
@@ -183 +229 @@
                         }
 
+                        // Free i-node found, save the bitmap
                         bitmap_block->dirty = true;
 
@@ -194 +241 @@
                         ext4_block_group_set_free_inodes_count(bg, sb, free_inodes);
 
+                        // Decrement unused i-nodes counter if supported
                         if (ext4_block_group_has_flag(bg, EXT4_BLOCK_GROUP_INODE_UNINIT)) {
                                 uint16_t unused_inodes = ext4_block_group_get_itable_unused(bg, sb);
@@ -200 +248 @@
                         }
 
+                        // Increment used directories counter
                         if (is_dir) {
                                 used_dirs++;
@@ -205 +254 @@
                         }
 
+                        // Save modified block group
                         bg_ref->dirty = true;
 
@@ -213 +263 @@
                         }
 
+                        // Update superblock
                         sb_free_inodes--;
                         ext4_superblock_set_free_inodes_count(sb, sb_free_inodes);
 
+                        // Compute the absolute i-nodex number
                         *index = ext4_ialloc_index_in_group2inode(sb, index_in_group, bgid);
 
@@ -222 +274 @@
                 }
 
-                // Not modified
+                // Block group not modified, put it and jump to the next block group
                 ext4_filesystem_put_block_group_ref(bg_ref);
                 ++bgid;