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 -- should be `/xyz/bar`. -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: common-issues-unsubscr...@hadoop.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org --------------------------------------------------------------------- To unsubscribe, e-mail: common-issues-unsubscr...@hadoop.apache.org For additional commands, e-mail: common-issues-h...@hadoop.apache.org
