ext4: update the cached overhead value in the superblock

If we (re-)calculate the file system overhead amount and it's
different from the on-disk s_overhead_clusters value, update the
on-disk version since this can take potentially quite a while on
bigalloc file systems.

Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@kernel.org

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 48dc2c3247add7a3efe30e5611f5e10b60e99f0a..a743b1e3b89ec2d58e8f427ba345e55801a62a41 100644 (file)
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -3068,6 +3068,7 @@ int ext4_fileattr_set(struct user_namespace *mnt_userns,
                      struct dentry *dentry, struct fileattr *fa);
 int ext4_fileattr_get(struct dentry *dentry, struct fileattr *fa);
 extern void ext4_reset_inode_seed(struct inode *inode);
+int ext4_update_overhead(struct super_block *sb);
 
 /* migrate.c */
 extern int ext4_ext_migrate(struct inode *);

diff --git a/fs/ext4/ioctl.c b/fs/ext4/ioctl.c
index 992229ca2d83036f9f388cd8b14874949949f086..ba44fa1be70aba8b8dfa30935ee2d9cae2af2e90 100644 (file)
--- a/fs/ext4/ioctl.c
+++ b/fs/ext4/ioctl.c
@@ -1652,3 +1652,19 @@ long ext4_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
        return ext4_ioctl(file, cmd, (unsigned long) compat_ptr(arg));
 }
 #endif
+
+static void set_overhead(struct ext4_super_block *es, const void *arg)
+{
+       es->s_overhead_clusters = cpu_to_le32(*((unsigned long *) arg));
+}
+
+int ext4_update_overhead(struct super_block *sb)
+{
+       struct ext4_sb_info *sbi = EXT4_SB(sb);
+
+       if (sb_rdonly(sb) || sbi->s_overhead == 0 ||
+           sbi->s_overhead == le32_to_cpu(sbi->s_es->s_overhead_clusters))
+               return 0;
+
+       return ext4_update_superblocks_fn(sb, set_overhead, &sbi->s_overhead);
+}

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index d08820fdfdee415a077f18ff25c03b32058f3bb7..1847b46af808375c559e65bb2d1a642de9953996 100644 (file)
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -5618,6 +5618,8 @@ static int ext4_fill_super(struct super_block *sb, struct fs_context *fc)
                ext4_msg(sb, KERN_INFO, "mounted filesystem with%s. "
                         "Quota mode: %s.", descr, ext4_quota_mode(sb));
 
+       /* Update the s_overhead_clusters if necessary */
+       ext4_update_overhead(sb);
        return 0;
 
 free_sbi: