From 1e8b212fe5dcee9d3dbb152d235f3c33458fb26e Mon Sep 17 00:00:00 2001
From: Jan Kara <jack@suse.cz>
Date: Tue, 12 Jun 2012 16:20:46 +0200
Subject: 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>
---
 fs/ext2/super.c | 33 +++++++++++++++++++++++++++++++++
 1 file changed, 33 insertions(+)

(limited to 'fs/ext2/super.c')

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)
 {
-- 
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