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Architecture - Punch and Extent Migration Requirements

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Note: The content on this page reflects the state of design of a Lustre feature at a particular point in time and may contain outdated information.

Punch functionality use cases
tag summary
checkvers optionally an inode version can be passed to the punch call and the punch will only take place if the inode, when locked has the version passed into the call. This enables handling races between modifying inodes and punching data from them.
access there is an ioctl to probe the presence of data in an extent. If any data in the extent has been punched, the ioctl will indicate so. The success case is that all data in the extent is present in the inode
punchextentmap an EA can be installed that points to or contains an extent map that describes the extents that have been punched from the file.
sparseispunched optionally, the recorded extents can be omitted and data is deemed punched if a sparse area is found in the file.
punchmigrate punched data can be migrated to another offset in another inode instead of freed

References

Punch and Extent Migration

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