ext4: FLEX_BG Kernel support v2.

This feature relaxes check restrictions on where each block groups meta
data is located within the storage media.  This allows for the allocation
of bitmaps or inode tables outside the block group boundaries in cases
where bad blocks forces us to look for new blocks which the owning block
group can not satisfy.  This will also allow for new meta-data allocation
schemes to improve performance and scalability.

Signed-off-by: Jose R. Santos <jrs@us.ibm.com>
Cc: <linux-ext4@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index dd4ff9c87358227b0b219ad29977896345b9c323..54450fa1af397954e81b2160cff86a94faf5dd5f 100644 (file)
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -1358,13 +1358,17 @@ static int ext4_check_descriptors (struct super_block * sb)
        ext4_fsblk_t inode_table;
        struct ext4_group_desc * gdp = NULL;
        int desc_block = 0;
+       int flexbg_flag = 0;
        int i;
 
+       if (EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_FLEX_BG))
+               flexbg_flag = 1;
+
        ext4_debug ("Checking group descriptors");
 
        for (i = 0; i < sbi->s_groups_count; i++)
        {
-               if (i == sbi->s_groups_count - 1)
+               if (i == sbi->s_groups_count - 1 || flexbg_flag)
                        last_block = ext4_blocks_count(sbi->s_es) - 1;
                else
                        last_block = first_block +
@@ -1409,7 +1413,8 @@ static int ext4_check_descriptors (struct super_block * sb)
                                   le16_to_cpu(gdp->bg_checksum));
                        return 0;
                }
-               first_block += EXT4_BLOCKS_PER_GROUP(sb);
+               if (!flexbg_flag)
+                       first_block += EXT4_BLOCKS_PER_GROUP(sb);
                gdp = (struct ext4_group_desc *)
                        ((__u8 *)gdp + EXT4_DESC_SIZE(sb));
        }

diff --git a/include/linux/ext4_fs.h b/include/linux/ext4_fs.h
index 722d4ef12bf30b897ab73cbae6050210c8f1417e..46b304d183454038669eec0f7dab4c9330cc8b48 100644 (file)
--- a/include/linux/ext4_fs.h
+++ b/include/linux/ext4_fs.h
@@ -682,13 +682,15 @@ static inline int ext4_valid_inum(struct super_block *sb, unsigned long ino)
 #define EXT4_FEATURE_INCOMPAT_META_BG          0x0010
 #define EXT4_FEATURE_INCOMPAT_EXTENTS          0x0040 /* extents support */
 #define EXT4_FEATURE_INCOMPAT_64BIT            0x0080
+#define EXT4_FEATURE_INCOMPAT_FLEX_BG          0x0200
 
 #define EXT4_FEATURE_COMPAT_SUPP       EXT2_FEATURE_COMPAT_EXT_ATTR
 #define EXT4_FEATURE_INCOMPAT_SUPP     (EXT4_FEATURE_INCOMPAT_FILETYPE| \
                                         EXT4_FEATURE_INCOMPAT_RECOVER| \
                                         EXT4_FEATURE_INCOMPAT_META_BG| \
                                         EXT4_FEATURE_INCOMPAT_EXTENTS| \
-                                        EXT4_FEATURE_INCOMPAT_64BIT)
+                                        EXT4_FEATURE_INCOMPAT_64BIT| \
+                                        EXT4_FEATURE_INCOMPAT_FLEX_BG)
 #define EXT4_FEATURE_RO_COMPAT_SUPP    (EXT4_FEATURE_RO_COMPAT_SPARSE_SUPER| \
                                         EXT4_FEATURE_RO_COMPAT_LARGE_FILE| \
                                         EXT4_FEATURE_RO_COMPAT_GDT_CSUM| \