ext4: snapshot list support

Implementation of multiple incremental snapshots. Snapshot inodes are chained on a list starting at the super block, both on-disk and in-memory, similar to the orphan inodes. Unlink and truncate of snapshot inodes on the list is not allowed, so an inode can never be chained on both orphan and snapshot lists. We make use of this fact to overload the in-memory inode field ext4_inode_info.i_orphan for the chaining of snapshots. Signed-off-by: Amir Goldstein <amir73il@users.sf.net> Signed-off-by: Yongqiang Yang <xiaoqiangnk@gmail.com>
amir73il · Jun 6, 2011 · 8db49fa · 8db49fa
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commit 8db49fa
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diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
@@ -1194,6 +1194,7 @@ struct ext4_sb_info {
 	struct block_device *journal_bdev;
 	struct mutex s_snapshot_mutex;		/* protects 2 fields below: */
 	struct inode *s_active_snapshot;	/* [ s_snapshot_mutex ] */
+	struct list_head s_snapshot_list;	/* [ s_snapshot_mutex ] */
 #ifdef CONFIG_JBD2_DEBUG
 	struct timer_list turn_ro_timer;	/* For turning read-only (crash simulation) */
 	wait_queue_head_t ro_wait_queue;	/* For people waiting for the fs to go read-only */