The recent thread on the list about strange df behavior made me go
look at how we were calculating s_overhead_blocks again, and I realized
that mkfs still doesn't set it. It seems like a simple thing to do;
just look at how many blocks are in use when mkfs is done.
Signed-off-by: Eric Sandeen <sandeen@xxxxxxxxxx>
---
However, I realize that resize2fs breaks this. And by the time
we have a populated fs, with bigalloc/meta/flex/whatnot, the
calculation of overhead gets very tricky again. (at least
for shrinking; growing is probably easier)
Ted, did you have a better patch for this? You added the
superblock field so maybe you had something in mind to keep it
up to date as the filesystem size changes?
diff --git a/misc/mke2fs.c b/misc/mke2fs.c
index bbf477a..3413bb2 100644
--- a/misc/mke2fs.c
+++ b/misc/mke2fs.c
@@ -2346,6 +2346,38 @@ static int create_quota_inodes(ext2_filsys fs)
return 0;
}
+/*
+ * Set the filesystem's metadata overhead - the number of blocks
+ * used for all mkfs-time metadata. We could carefully account
+ * for all blocks, or do it the easy way: See how many blocks
+ * have been used by mkfs, at the end of mkfs. Add the space used
+ * by the root dir and lost+found back in.
+ */
+void set_fs_overhead(ext2_filsys fs) {
+ unsigned int overhead;
+ struct ext2_inode inode;
+ ext2_ino_t inum;
+ blk64_t iblocks;
+
+ /* overhead is everything mkfs has used ... */
+ overhead = ext2fs_blocks_count(fs->super) -
+ ext2fs_free_blocks_count(fs->super);
+
+ /* ... not counting / and /lost+found */
+ if (!ext2fs_read_inode(fs, EXT2_ROOT_INO, &inode)) {
+ iblocks = ext2fs_inode_i_blocks(fs, &inode);
+ overhead -= (iblocks << 9) / fs->blocksize;
+ }
+
+ if (!ext2fs_lookup(fs, EXT2_ROOT_INO, "lost+found", 10, 0, &inum) &&
+ !ext2fs_read_inode(fs, inum, &inode)) {
+ iblocks = ext2fs_inode_i_blocks(fs, &inode);
+ overhead -= (iblocks << 9) / fs->blocksize;
+ }
+
+ fs->super->s_overhead_blocks = overhead;
+}
+
int main (int argc, char *argv[])
{
errcode_t retval = 0;
@@ -2733,6 +2764,8 @@ no_journal:
EXT4_FEATURE_RO_COMPAT_QUOTA))
create_quota_inodes(fs);
+ set_fs_overhead(fs);
+
if (!quiet)
printf(_("Writing superblocks and "
"filesystem accounting information: "));
--
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