Changeset 447201e in mainline

Timestamp:

2015-04-16T19:34:06Z (9 years ago)

Author:

Maurizio Lombardi <m.lombardi85@…>

Branches:

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

Children:

7f29575

Parents:

6dd7f65

Message:

libext4: adds a function that, given a block group ref, calculates the number of blocks reserved to GDT+superblock backups.

Location:

uspace/lib/ext4

Files:

• libext4_filesystem.c (modified) (2 diffs)
• libext4_filesystem.h (modified) (1 diff)

uspace/lib/ext4/libext4_filesystem.c

@@ -40 +40 @@
 #include <malloc.h>
 #include <ipc/vfs.h>
+#include <align.h>
 #include "libext4.h"
 
@@ -521 +522 @@
         
         return crc;
+}
+
+/* Check if n is a power of p */
+static bool is_power_of(uint32_t n, unsigned p)
+{
+        if (p == 1 && n != p)
+                return false;
+
+        while (n != p) {
+                if (n < p)
+                        return false;
+                else if ((n % p) != 0)
+                        return false;
+
+                n /= p;
+        }
+
+        return true;
+}
+
+/** Get the number of blocks used by superblock + gdt + reserved gdt backups
+ *
+ * @param bg    Pointer to block group
+ *
+ * @return      Number of blocks
+ */
+uint32_t ext4_block_group_get_backup_blocks(ext4_block_group_ref_t *bg)
+{
+        uint32_t const idx = bg->index;
+        uint32_t r = 0;
+        bool has_backups = false;
+        ext4_superblock_t *sb = bg->fs->superblock;
+
+        /* First step: determine if the block group contains the backups */
+
+        if (idx <= 1)
+                has_backups = true;
+        else {
+                if (ext4_superblock_has_feature_compatible(sb,
+                    EXT4_FEATURE_COMPAT_SPARSE_SUPER2)) {
+                        uint32_t g1, g2;
+
+                        ext4_superblock_get_backup_groups_sparse2(sb,
+                            &g1, &g2);
+
+                        if (idx == g1 || idx == g2)
+                                has_backups = true;
+                } else if (!ext4_superblock_has_feature_read_only(sb,
+                    EXT4_FEATURE_RO_COMPAT_SPARSE_SUPER)) {
+                        /* Very old fs were all block groups have
+                         * superblock and block descriptors backups.
+                         */
+                        has_backups = true;
+                } else {
+                        if ((idx & 1) && (is_power_of(idx, 3) ||
+                            is_power_of(idx, 5) || is_power_of(idx, 7)))
+                                has_backups = true;
+                }
+        }
+
+        if (has_backups) {
+                uint32_t bg_count;
+                uint32_t bg_desc_sz;
+                uint32_t gdt_table; /* Size of the GDT in blocks */
+                uint32_t block_size = ext4_superblock_get_block_size(sb);
+
+                /* Now we know that this block group has backups,
+                 * we have to compute how many blocks are reserved
+                 * for them
+                 */
+
+                if (idx == 0 && block_size == 1024) {
+                        /* Special case for first group were the boot block
+                         * resides
+                         */
+                        r++;
+                }
+
+                /* This accounts for the superblock */
+                r++;
+
+                /* Add the number of blocks used for the GDT */
+                bg_count = ext4_superblock_get_block_group_count(sb);
+                bg_desc_sz = ext4_superblock_get_desc_size(sb);
+                gdt_table = ROUND_UP(bg_count * bg_desc_sz, block_size) /
+                    block_size;
+
+                r += gdt_table;
+
+                /* And now the number of reserved GDT blocks */
+                r += ext4_superblock_get_reserved_gdt_blocks(sb);
+        }
+
+        return r;
 }
 

uspace/lib/ext4/libext4_filesystem.h

@@ -64 +64 @@
 extern int ext4_filesystem_append_inode_block(ext4_inode_ref_t *, uint32_t *,
     uint32_t *);
+uint32_t ext4_block_group_get_backup_blocks(ext4_block_group_ref_t *bg);
 
 #endif