Hello All，
Currently, I am seeing the the make_ext4fs code of
android，the source code is located at system/extras/ext4_utils
I have some question, as following, can somebody help me to explain
these questions? Thanks a lot!
1. The method of compute journal blocks, why divide 64 :
static u32 compute_journal_blocks()
{
u32 journal_blocks = DIV_ROUND_UP(info.len, info.block_size) / 64;
// is here, why divide 64 ???
if (journal_blocks < 1024)
journal_blocks = 1024;
if (journal_blocks > 32768)
journal_blocks = 32768;
return journal_blocks;
}
2. The method of compute jbg_desc_reserve_blocks , why multiply by 1024:
static u32 compute_bg_desc_reserve_blocks()
{
u32 blocks = DIV_ROUND_UP(info.len, info.block_size);
u32 block_groups = DIV_ROUND_UP(blocks, info.blocks_per_group);
u32 bg_desc_blocks = DIV_ROUND_UP(block_groups * sizeof(struct
ext2_group_desc),
info.block_size);
u32 bg_desc_reserve_blocks =
DIV_ROUND_UP(block_groups * 1024 * sizeof(struct
ext2_group_desc), // is here , why multiply by 1024 ???
info.block_size) - bg_desc_blocks;
if (bg_desc_reserve_blocks > info.block_size / sizeof(u32))
bg_desc_reserve_blocks = info.block_size / sizeof(u32);
return bg_desc_reserve_blocks;
}
3. About compute_inodes function , why divide 4 ??
static u32 compute_inodes()
{
return DIV_ROUND_UP(info.len, info.block_size) / 4; // is here
why divide 4 ??
}
yu.xing
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