From af7e95c32cea40c1e443ae301e64b27f068b4915 Mon Sep 17 00:00:00 2001

From: Paulo Alcantara <pcacjr@zytor.com>

Date: Wed, 11 Oct 2017 07:00:31 -0400

Subject: [PATCH] ext4: Fix 64bit feature

As per ext4 specification:

> In ext2, ext3, and ext4 (when the 64bit feature is not enabled), the

> block group descriptor was only 32 bytes long and therefore ends at

> bg_checksum. On an ext4 filesystem with the 64bit feature enabled, the

> block group descriptor expands to at least the 64 bytes described below;

> the size is stored in the superblock.

Since block group descriptor has been expanded to 64 bytes long (when 64

bit feature is enabled), we cannot index ext2_group_desc and return it

*directly* -- as we did it in ext2_get_group_desc -- it's still 32 bytes

long.

Instead, use s_desc_size field from superblock to correctly index and

return block group descriptors.

Cc: H. Peter Anvin <hpa@zytor.com>

Cc: Gene Cumm <gene.cumm@gmail.com>

Signed-off-by: Paulo Alcantara <pcacjr@zytor.com>

---

 core/fs/ext2/ext2.c    | 23 ++++++++++++++---------

 core/fs/ext2/ext2_fs.h |  1 +

 2 files changed, 15 insertions(+), 9 deletions(-)

diff --git a/core/fs/ext2/ext2.c b/core/fs/ext2/ext2.c

index 76bd1d5..4bc0a53 100644

--- a/core/fs/ext2/ext2.c

+++ b/core/fs/ext2/ext2.c

@@ -25,22 +25,17 @@ static enum dirent_type ext2_cvt_type(unsigned int d_file_type)

 	return inode_type[d_file_type];

 }

-/*

- * get the group's descriptor of group_num

- */

-static const struct ext2_group_desc *

-ext2_get_group_desc(struct fs_info *fs, uint32_t group_num)

+static const void *__ext2_get_group_desc(struct fs_info *fs, uint32_t group_num)

 {

     struct ext2_sb_info *sbi = EXT2_SB(fs);

     uint32_t desc_block, desc_index;

-    const struct ext2_group_desc *desc_data_block;

+    uint8_t *p;

     if (group_num >= sbi->s_groups_count) {

 	printf ("ext2_get_group_desc"

 		"block_group >= groups_count - "

 		"block_group = %d, groups_count = %d",

 		group_num, sbi->s_groups_count);

-

 	return NULL;

     }

@@ -49,8 +44,17 @@ ext2_get_group_desc(struct fs_info *fs, uint32_t group_num)

     desc_block += sbi->s_first_data_block + 1;

-    desc_data_block = get_cache(fs->fs_dev, desc_block);

-    return &desc_data_block[desc_index];

+    p = get_cache(fs->fs_dev, desc_block);

+    return p + sbi->s_desc_size * desc_index;

+}

+

+/*

+ * get the group's descriptor of group_num

+ */

+static inline const struct ext2_group_desc *

+ext2_get_group_desc(struct fs_info *fs, uint32_t group_num)

+{

+    return __ext2_get_group_desc(fs, group_num);

 }

 /*

@@ -306,6 +310,7 @@ static int ext2_fs_init(struct fs_info *fs)

     if (sb.s_desc_size < sizeof(struct ext2_group_desc))

 	sb.s_desc_size = sizeof(struct ext2_group_desc);

     sbi->s_desc_per_block   = BLOCK_SIZE(fs) / sb.s_desc_size;

+    sbi->s_desc_size = sb.s_desc_size;

     sbi->s_groups_count     = (sb.s_blocks_count - sb.s_first_data_block

 			       + EXT2_BLOCKS_PER_GROUP(fs) - 1)

 	                      / EXT2_BLOCKS_PER_GROUP(fs);

diff --git a/core/fs/ext2/ext2_fs.h b/core/fs/ext2/ext2_fs.h

index 803a995..d8d07eb 100644

--- a/core/fs/ext2/ext2_fs.h

+++ b/core/fs/ext2/ext2_fs.h

@@ -278,6 +278,7 @@ struct ext2_sb_info {

     uint32_t s_first_data_block;	/* First Data Block */

     int      s_inode_size;

     uint8_t  s_uuid[16];	/* 128-bit uuid for volume */

+    int      s_desc_size;	/* size of group descriptor */

 };

 static inline struct ext2_sb_info *EXT2_SB(struct fs_info *fs)

-- 

2.7.4.GIT