ext2: Implement freezing

The only missing piece to make freezing work reliably with ext2 is to
stop iput() of unlinked inode from deleting the inode on frozen filesystem.
So add a necessary protection to ext2_evict_inode().

We also provide appropriate ->freeze_fs and ->unfreeze_fs functions.

Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 33 insertions, 0 deletions

diff --git a/fs/ext2/super.c b/fs/ext2/super.c
index 5df3d2d8169c..15761e638dae 100644
--- a/fs/ext2/super.c
+++ b/fs/ext2/super.c
@@ -42,6 +42,8 @@ static void ext2_sync_super(struct super_block *sb,
 static int ext2_remount (struct super_block * sb, int * flags, char * data);
 static int ext2_statfs (struct dentry * dentry, struct kstatfs * buf);
 static int ext2_sync_fs(struct super_block *sb, int wait);
+static int ext2_freeze(struct super_block *sb);
+static int ext2_unfreeze(struct super_block *sb);
 
 void ext2_error(struct super_block *sb, const char *function,
                 const char *fmt, ...)
@@ -305,6 +307,8 @@ static const struct super_operations ext2_sops = {
         .evict_inode    = ext2_evict_inode,
         .put_super      = ext2_put_super,
         .sync_fs        = ext2_sync_fs,
+        .freeze_fs      = ext2_freeze,
+        .unfreeze_fs    = ext2_unfreeze,
         .statfs         = ext2_statfs,
         .remount_fs     = ext2_remount,
         .show_options   = ext2_show_options,
@@ -1200,6 +1204,35 @@ static int ext2_sync_fs(struct super_block *sb, int wait)
         return 0;
 }
 
+static int ext2_freeze(struct super_block *sb)
+{
+        struct ext2_sb_info *sbi = EXT2_SB(sb);
+
+        /*
+         * Open but unlinked files present? Keep EXT2_VALID_FS flag cleared
+         * because we have unattached inodes and thus filesystem is not fully
+         * consistent.
+         */
+        if (atomic_long_read(&sb->s_remove_count)) {
+                ext2_sync_fs(sb, 1);
+                return 0;
+        }
+        /* Set EXT2_FS_VALID flag */
+        spin_lock(&sbi->s_lock);
+        sbi->s_es->s_state = cpu_to_le16(sbi->s_mount_state);
+        spin_unlock(&sbi->s_lock);
+        ext2_sync_super(sb, sbi->s_es, 1);
+
+        return 0;
+}
+
+static int ext2_unfreeze(struct super_block *sb)
+{
+        /* Just write sb to clear EXT2_VALID_FS flag */
+        ext2_write_super(sb);
+
+        return 0;
+}
 
 void ext2_write_super(struct super_block *sb)
 {