ext4: fix long mount times on very big file systems (0548bbb8) · Commits · 戴 / test

Commit 8aeb00ff85a: "ext4: fix overhead calculation used by ext4_statfs()" introduced a O(n**2) calculation which makes very large file systems take forever to mount. Fix this with an optimization for non-bigalloc file systems. (For bigalloc file systems the overhead needs to be set in the the superblock.) Signed-off-by:

"Theodore Ts'o" <tytso@mit.edu> Cc: stable@vger.kernel.org

fs/ext4/super.c

+4 −0

Original line number	Diff line number	Diff line
		@@ -3120,6 +3120,10 @@ static int count_overhead(struct super_block *sb, ext4_group_t grp,
		ext4_group_t i, ngroups = ext4_get_groups_count(sb);
		int s, j, count = 0;

		if (!EXT4_HAS_RO_COMPAT_FEATURE(sb, EXT4_FEATURE_RO_COMPAT_BIGALLOC))
		return (ext4_bg_has_super(sb, grp) + ext4_bg_num_gdb(sb, grp) +
		sbi->s_itb_per_group + 2);

		first_block = le32_to_cpu(sbi->s_es->s_first_data_block) +
		(grp * EXT4_BLOCKS_PER_GROUP(sb));
		last_block = first_block + EXT4_BLOCKS_PER_GROUP(sb) - 1;

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