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Description: Fix ext4 block group handling
Backported distantly from grub2, particularly:
https://git.savannah.gnu.org/cgit/grub.git/commit/?id=e20aa39ea4298011ba716087713cff26c6c52006
Author: Colin Watson <cjwatson@debian.org>
Bug-Debian: https://bugs.debian.org/511121
Last-Update: 2018-10-25
Index: b/stage2/fsys_ext2fs.c
===================================================================
--- a/stage2/fsys_ext2fs.c
+++ b/stage2/fsys_ext2fs.c
@@ -41,6 +41,8 @@
typedef unsigned short __u16;
typedef __signed__ int __s32;
typedef unsigned int __u32;
+typedef __signed__ long long __s64;
+typedef unsigned long long __u64;
/*
* Constants relative to the data blocks, from ext2_fs.h
@@ -51,6 +53,13 @@
#define EXT2_TIND_BLOCK (EXT2_DIND_BLOCK + 1)
#define EXT2_N_BLOCKS (EXT2_TIND_BLOCK + 1)
+/* Superblock filesystem feature flags (RO compatible) */
+#define EXT2_FEATURE_RO_COMPAT_SPARSE_SUPER 0x0001
+
+/* Superblock filesystem feature flags (back-incompatible) */
+#define EXT2_FEATURE_INCOMPAT_META_BG 0x0010
+#define EXT4_FEATURE_INCOMPAT_64BIT 0x0080
+
/* Inode flags */
#define EXT4_EXTENTS_FL 0x00080000 /* Inode uses extents */
@@ -122,7 +131,7 @@
__u32 s_hash_seed[4]; /* HTREE hash seed */
__u8 s_def_hash_version; /* Default hash version to use */
__u8 s_jnl_backup_type; /* Default type of journal backup */
- __u16 s_reserved_word_pad;
+ __u16 s_desc_size; /* Group desc. size: INCOMPAT_64BIT */
__u32 s_default_mount_opts;
__u32 s_first_meta_bg; /* First metablock group */
__u32 s_mkfs_time; /* When the filesystem was created */
@@ -284,13 +293,20 @@
#define PATH_MAX 1024 /* include/linux/limits.h */
#define MAX_LINK_COUNT 5 /* number of symbolic links to follow */
+/* Information about a "mounted" ext2 filesystem. */
+struct ext2_data
+ {
+ int log_group_desc_size;
+ };
+
/* made up, these are pointers into FSYS_BUF */
/* read once, always stays there: */
#define SUPERBLOCK \
((struct ext2_super_block *)(FSYS_BUF))
+#define FS_DATA \
+ ((struct ext2_data *)((int)SUPERBLOCK + sizeof(struct ext2_super_block)))
#define GROUP_DESC \
- ((struct ext2_group_desc *) \
- ((int)SUPERBLOCK + sizeof(struct ext2_super_block)))
+ ((int)((int)FS_DATA + sizeof(struct ext2_data)))
#define INODE \
((struct ext2_inode *)((int)GROUP_DESC + EXT2_BLOCK_SIZE(SUPERBLOCK)))
#define DATABLOCK1 \
@@ -357,6 +373,20 @@
|| SUPERBLOCK->s_magic != EXT2_SUPER_MAGIC)
retval = 0;
+ if (SUPERBLOCK->s_rev_level != EXT2_GOOD_OLD_REV
+ && (SUPERBLOCK->s_feature_incompat & EXT4_FEATURE_INCOMPAT_64BIT)
+ && SUPERBLOCK->s_desc_size != 0
+ && (SUPERBLOCK->s_desc_size & (SUPERBLOCK->s_desc_size - 1)) == 0
+ && (SUPERBLOCK->s_desc_size & 0x1fe0))
+ {
+ __u16 b = SUPERBLOCK->s_desc_size;
+ for (FS_DATA->log_group_desc_size = 0;
+ b != (1 << FS_DATA->log_group_desc_size);
+ FS_DATA->log_group_desc_size++);
+ }
+ else
+ FS_DATA->log_group_desc_size = 5;
+
return retval;
}
@@ -623,6 +653,32 @@
return INODE->i_blocks == ea_blocks;
}
+static int
+is_power_of (__u64 a, __u64 b)
+{
+ __u64 c;
+ /* Prevent overflow assuming b < 8. */
+ if (a >= (1LL << 60))
+ return 0;
+ for (c = 1; c <= a; c *= b);
+ return (c == a);
+}
+
+static int
+ext2fs_group_has_super_block (__u64 group)
+{
+ if (!(SUPERBLOCK->s_feature_ro_compat & EXT2_FEATURE_RO_COMPAT_SPARSE_SUPER))
+ return 1;
+ /* Algorithm looked up in Linux source. */
+ if (group <= 1)
+ return 1;
+ /* Even number is never a power of odd number. */
+ if (!(group & 1))
+ return 0;
+ return (is_power_of (group, 7) || is_power_of (group, 5) ||
+ is_power_of (group, 3));
+}
+
/* preconditions: ext2fs_mount already executed, therefore supblk in buffer
* known as SUPERBLOCK
* returns: 0 if error, nonzero iff we were able to find the file successfully
@@ -635,8 +691,9 @@
{
int current_ino = EXT2_ROOT_INO; /* start at the root */
int updir_ino = current_ino; /* the parent of the current directory */
- int group_id; /* which group the inode is in */
- int group_desc; /* fs pointer to that group */
+ __u64 full_offset;
+ __u64 group_id; /* which group the inode is in */
+ __u64 group_desc; /* fs pointer to that group */
int desc; /* index within that group */
int ino_blk; /* fs pointer of the inode's information */
int str_chk = 0; /* used to hold the results of a string compare */
@@ -675,23 +732,37 @@
/* look up an inode */
group_id = (current_ino - 1) / (SUPERBLOCK->s_inodes_per_group);
- group_desc = group_id >> log2 (EXT2_DESC_PER_BLOCK (SUPERBLOCK));
- desc = group_id & (EXT2_DESC_PER_BLOCK (SUPERBLOCK) - 1);
+ full_offset = group_id << FS_DATA->log_group_desc_size;
+ group_desc = full_offset >> EXT2_BLOCK_SIZE_BITS (SUPERBLOCK);
+ desc = full_offset & (EXT2_BLOCK_SIZE (SUPERBLOCK) - 1);
+ if ((SUPERBLOCK->s_feature_incompat & EXT2_FEATURE_INCOMPAT_META_BG)
+ && group_desc >= SUPERBLOCK->s_first_meta_bg)
+ {
+ __u64 first_block_group;
+ /* Find the first block group for which a descriptor is stored in
+ the given block. */
+ first_block_group = (group_desc << (EXT2_BLOCK_SIZE_BITS (SUPERBLOCK)
+ - FS_DATA->log_group_desc_size));
+ group_desc = first_block_group * SUPERBLOCK->s_blocks_per_group;
+ if (ext2fs_group_has_super_block (first_block_group))
+ group_desc++;
+ }
+ else
+ /* Superblock. */
+ group_desc++;
#ifdef E2DEBUG
printf ("ipg=%d, dpb=%d\n", SUPERBLOCK->s_inodes_per_group,
EXT2_DESC_PER_BLOCK (SUPERBLOCK));
printf ("group_id=%d group_desc=%d desc=%d\n", group_id, group_desc, desc);
#endif /* E2DEBUG */
- if (!ext2_rdfsb (
- (WHICH_SUPER + group_desc + SUPERBLOCK->s_first_data_block),
- (int) GROUP_DESC))
+ if (!ext2_rdfsb (SUPERBLOCK->s_first_data_block + group_desc, GROUP_DESC))
{
return 0;
}
- gdp = GROUP_DESC;
+ gdp = (struct ext2_group_desc *)(GROUP_DESC + desc);
inodes_per_block = EXT2_BLOCK_SIZE (SUPERBLOCK) / EXT2_INODE_SIZE(SUPERBLOCK);
inode_offset = ((current_ino - 1) % (SUPERBLOCK->s_inodes_per_group));
- ino_blk = gdp[desc].bg_inode_table + (inode_offset / inodes_per_block);
+ ino_blk = gdp->bg_inode_table + (inode_offset / inodes_per_block);
#ifdef E2DEBUG
printf ("inode table fsblock=%d\n", ino_blk);
#endif /* E2DEBUG */
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