Investigate hanging metadata calls

[jcheng5]

@kevinhankens encountered a behavior where doing a dd 1TB write to EFS, caused ls of the same directory to block until the dd completes. Doing a dd of a different directory (a subdirectory, actually) did not block.

[jcheng5]

https://docs.aws.amazon.com/efs/latest/ug/troubleshooting-efs-mounting.html#mount-unresponsive

Mount Does Not Respond

An Amazon EFS mount appears unresponsive. For example, commands like ls hang.

Action to take

This error can occur if another application is writing large amounts of data to the file system. Access to the files that are being written might be blocked until the operation is complete. In general, any commands or applications that attempt to access files that are being written to might appear to hang. For example, the ls command might hang when it gets to the file that is being written. This result is because some Linux distributions alias the ls command so that it retrieves file attributes in addition to listing the directory contents.