[PATCH v2 0/9] xfsrestore dirent limitations and scaling issues

[wkendall@sgi.com]

The first two patches in this series remove dirent limitations that
exist in the current xfsrestore, allowing restore to now handle 4
billion directory entries. Restore would map 200 GB of memory to do
so, so don't go thinking this is a good idea. :)  (These two patches
were previously submitted to the list but I've made some changes to
them as suggested by Alex Elder.)

The remaining patches mostly deal with improving restore
performance, most noticeably on dumps containing upwards of 10
million inodes/dirents.  This resulted in a 50% improvement in the
time required to build restore's node table (a mmap'd representation
of the dump's directory structure), so for interactive restores and
restoring sub-directories this is very helpful. For full restores
with millions of files the overall restore time is dominated by
creating inodes and laying down the data, so the improvements here
would be less noticeable.

For dumps with lots of hard links, these changes fix a bug that was
causing xfsrestore to constantly have to map and unmap segments of
the node table, leading to horrible performance.

Several of these patches modify the on-disk state information that
xfsrestore leaves around for resuming restores. The final patch adds
versioning information to the on-disk state to detect cases where
the user tries to resume a restore with an incompatible version of
xfsrstore (or an incompatible system).

Bill

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