Re: [PATCH] ext4 extent support

[Marco Gerards <mgerards@xs4all.nl>]

Hi Bean,

Bean <bean123ch@gmail.com> writes:

> This patch add support for extents in ext4.

This is really great! :D

Can you also provide a changelog entry?

> diff --git a/fs/ext2.c b/fs/ext2.c
> index 22fd272..3518dcf 100644
> --- a/fs/ext2.c
> +++ b/fs/ext2.c
> @@ -86,6 +86,8 @@
>  #define EXT3_JOURNAL_FLAG_DELETED	4
>  #define EXT3_JOURNAL_FLAG_LAST_TAG	8
>  
> +#define EXT4_EXTENTS_FLAG		0x80000
> +
>  /* The ext2 superblock.  */
>  struct grub_ext2_sblock
>  {
> @@ -226,6 +228,33 @@ struct grub_ext3_journal_sblock
>    grub_uint32_t start;
>  };
>  
> +#define EXT4_EXT_MAGIC		0xf30a
> +
> +struct grub_ext4_extent_header
> +{
> +  grub_uint16_t magic;
> +  grub_uint16_t entries;
> +  grub_uint16_t max;
> +  grub_uint16_t depth;
> +  grub_uint32_t generation;
> +};
> +
> +struct grub_ext4_extent
> +{
> +  grub_uint32_t block;
> +  grub_uint16_t len;
> +  grub_uint16_t start_hi;
> +  grub_uint32_t start;
> +};
> +
> +struct grub_ext4_extent_idx
> +{
> +  grub_uint32_t block;
> +  grub_uint32_t leaf;
> +  grub_uint16_t leaf_hi;
> +  grub_uint16_t unused;
> +};
> +
>  struct grub_fshelp_node
>  {
>    struct grub_ext2_data *data;
> @@ -262,6 +291,46 @@ grub_ext2_blockgroup (struct grub_ext2_data *data, int group,
>  			 sizeof (struct grub_ext2_block_group), (char *) blkgrp);
>  }
>  
> +static struct grub_ext4_extent_header *
> +grub_ext4_find_leaf (struct grub_ext2_data *data,
> +                     struct grub_ext4_extent_header *ext_block,
> +                     grub_uint32_t fileblock)
> +{
> +  char buf[EXT2_BLOCK_SIZE(data)];
> +  struct grub_ext4_extent_idx *index;
> +
> +  while (1)
> +    {
> +      int i;
> +      grub_disk_addr_t block;
> +
> +      index = (struct grub_ext4_extent_idx *) (ext_block + 1);
> +
> +      if (grub_le_to_cpu16(ext_block->magic) != EXT4_EXT_MAGIC)
> +        return 0;
> +
> +      if (ext_block->depth == 0)
> +        return ext_block;
> +
> +      for (i = 0; i < grub_le_to_cpu16 (ext_block->entries); i++)
> +        {
> +          if (fileblock < grub_le_to_cpu32(index[i].block))
> +            break;
> +        }
> +
> +      if (i == 0)
> +        return 0;
> +
> +      block = grub_le_to_cpu16 (index[i].leaf_hi);
> +      block = (block << 32) + grub_le_to_cpu32 (index[i].leaf);
> +      if (grub_disk_read (data->disk,
> +                          block << LOG2_EXT2_BLOCK_SIZE (data),
> +                          0, sizeof (buf), buf))
> +        return 0;
> +
> +      ext_block = (struct grub_ext4_extent_header *) buf;
> +    }
> +}
>  
>  static grub_disk_addr_t
>  grub_ext2_read_block (grub_fshelp_node_t node, grub_disk_addr_t fileblock)
> @@ -272,6 +341,41 @@ grub_ext2_read_block (grub_fshelp_node_t node, grub_disk_addr_t fileblock)
>    unsigned int blksz = EXT2_BLOCK_SIZE (data);
>    int log2_blksz = LOG2_EXT2_BLOCK_SIZE (data);
>    
> +  if (inode->flags & EXT4_EXTENTS_FLAG)
> +    {
> +      struct grub_ext4_extent_header *leaf;
> +      struct grub_ext4_extent *ext;
> +      int i;
> +
> +      leaf = grub_ext4_find_leaf (data,
> +                                  (struct grub_ext4_extent_header *) inode->blocks.dir_blocks,
> +                                  fileblock);
> +      if (! leaf)
> +        {
> +          grub_error (GRUB_ERR_BAD_FS, "invalid extent");
> +          return -1;
> +        }
> +
> +      ext = (struct grub_ext4_extent *) (leaf + 1);
> +      for (i = 0; i < grub_le_to_cpu16 (leaf->entries); i++)
> +        if ((fileblock >= grub_le_to_cpu32 (ext[i].block)) &&
> +            (fileblock < grub_le_to_cpu32 (ext[i].block) +
> +             grub_le_to_cpu16 (ext[i].len)) &&
> +            ((grub_le_to_cpu16 (ext[i].len) >> 15) == 0))
> +          {
> +            grub_disk_addr_t start;
> +
> +            start = grub_le_to_cpu16 (ext[i].start_hi);
> +            start = (start << 32) + grub_le_to_cpu32 (ext[i].start);
> +            return fileblock - grub_le_to_cpu32 (ext[i].block) + start;
> +          }
> +
> +
> +
> +      grub_printf ("HH\n");

Whoops? ;-)

> +      return grub_error (GRUB_ERR_NOT_IMPLEMENTED_YET,
> +                         "ext2fs doesn't support extents");

Why the error?  I thought you have added extent support?  Doesn't this
mean the extent has another error of some kind?

--
Marco