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https://issues.apache.org/jira/browse/HDFS-16972?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17713179#comment-17713179
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ASF GitHub Bot commented on HDFS-16972:
---------------------------------------
szetszwo commented on code in PR #5532:
URL: https://github.com/apache/hadoop/pull/5532#discussion_r1168961332
##########
hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/INodeReference.java:
##########
@@ -35,32 +35,45 @@
import org.apache.hadoop.security.AccessControlException;
/**
- * An anonymous reference to an inode.
- *
+ * A reference to an inode.
+ * <p>
* This class and its subclasses are used to support multiple access paths.
* A file/directory may have multiple access paths when it is stored in some
- * snapshots and it is renamed/moved to other locations.
- *
+ * snapshots, and it is renamed/moved to other locations.
+ * <p>
* For example,
- * (1) Suppose we have /abc/foo, say the inode of foo is
inode(id=1000,name=foo)
- * (2) create snapshot s0 for /abc
+ * (1) Suppose we have /abc/foo and the inode is inode(id=1000,name=foo).
+ * Suppose foo is created after snapshot s0,
+ * i.e. foo is not in s0 and inode(id=1000,name=foo)
+ * is in the create-list of /abc for the s0 diff entry.
+ * (2) Create snapshot s1, s2 for /abc, i.e. foo is in s1 and s2.
+ * Suppose sDst is the last snapshot /xyz.
* (3) mv /abc/foo /xyz/bar, i.e. inode(id=1000,name=...) is renamed from "foo"
* to "bar" and its parent becomes /xyz.
- *
- * Then, /xyz/bar and /abc/.snapshot/s0/foo are two different access paths to
- * the same inode, inode(id=1000,name=bar).
- *
+ * <p>
+ * Then, /xyz/bar, /abc/.snapshot/s1/foo and /abc/.snapshot/s2/foo
+ * are different access paths to the same inode, inode(id=1000,name=bar).
+ * <p>
* With references, we have the following
- * - /abc has a child ref(id=1001,name=foo).
- * - /xyz has a child ref(id=1002)
- * - Both ref(id=1001,name=foo) and ref(id=1002) point to another reference,
- * ref(id=1003,count=2).
- * - Finally, ref(id=1003,count=2) points to inode(id=1000,name=bar).
- *
- * Note 1: For a reference without name, e.g. ref(id=1002), it uses the name
- * of the referred inode.
+ * - The source /abc/foo inode(id=1000,name=foo) is replaced with
+ * a WithName(name=foo,lastSnapshot=s2) and then it is moved
+ * to the delete-list of /abc for the s2 diff entry.
+ * The replacement also replaces inode(id=1000,name=foo)
+ * in the create-list of /abc for the s0 diff entry with the WithName.
+ * The same as before, /abc/foo is in s1 and s2, but not in s0.
+ * - The destination /xyz adds a child DstReference(dstSnapshot=sDst).
+ * DstReference is added to the create-list of /xyz for the sDst diff entry.
+ * /abc/bar is not in sDst.
Review Comment:
Oops, it is a typo
> Delete a snapshot may deleteCurrentFile
> ---------------------------------------
>
> Key: HDFS-16972
> URL: https://issues.apache.org/jira/browse/HDFS-16972
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: snapshots
> Reporter: Tsz-wo Sze
> Assignee: Tsz-wo Sze
> Priority: Major
> Labels: pull-request-available
>
> We found one case the when deleting a snapshot (with ordered snapshot
> deletion disabled), it can incorrectly delete some files in the current state.
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