[LUDOC-531] lfs setstripe should warn when layout does not go to EOF

• Type: Bug
• Resolution: Unresolved
• Priority: Minor
• Severity: 3
• Assignee: Rajeev Mishra
• Reporter: Rajeev Mishra

Description

It is possible to specify a file layout with `lfs setstripe` that does not allow a file to be written the the max EOF. This is especially easy to trip up when specifying a DoM layout because it is generally assumed that the remaining layout will automatically go to the OSTs, but it does not.

For example a user might execute the following command to create a DoM file:
lfs setstripe -E 1M -L mdt /mnt/lustre/domdir

However, the file won't be writeable beyond 1 MIB because there is no extent defined beyond the DoM component. Instead the user should run:
lfs setstripe -E 1M -L mdt -E -1 /mnt/lustre/domdir

That will allow the file to have a stripe beyond the DoM component to max EOF (-1).

This usability quirk means that users can easily shoot themselves in the foot. We should contemplate either making the non-EOF case an error (that could be overridden for users that truly don't want striping to EOF) or at least emit a warning when they create a layout short of EOF.