Zach Brown b51511466a scoutfs: add inodes_since ioctl ...

Add the ioctl that let's us find out about inodes that have changed
since a given sequence number.

A sequence number is added to the btree items so that we can track the
tree update that it last changed in.  We update this as we modify
items and maintain it across item copying for splits and merges.

The big change is using the parent item ref and item sequence numbers
to guide iteration over items in the tree.  The easier change is to have
the current iteration skip over items whose sequence number is too old.

The more subtle change has to do with how iteration is terminated.  The
current termination could stop when it doesn't find an item because that
could only happen at the final leaf.  When we're ignoring items with old
seqs this can happen at the end of any leaf.  So we change iteration to
keep advancing through leaf blocks until it crosses the last key value.

We add an argument to btree walking which communicates the next key that
can be used to continue iterating from the next leaf block.  This works
for the normal walk case as well as the seq walking case where walking
terminates prematurely in an interior node full of parent items with old
seqs.

Now that we're more robustly advancing iteration with btree walk calls
and the next key we can get rid fo the 'next_leaf' hack which was trying
to do the same thing inside the btree walk code.  It wasn't right for
the seq walking case and was pretty fiddly.

The next_key increment could wrap the maximal key at the right spine of
the tree so we have _inc saturate instead of wrap.

And finally, we want these inode scans to not have to skip over all the
other items associated with each inode as it walks looking for inodes
with the given sequence number.  We change the item sort order to first
sort by type instead of by inode.  We've wanted this more generally to
isolate item types that have different access patterns.

Signed-off-by: Zach Brown <zab@versity.com>

2016-07-05 14:46:20 -07:00

kmod

scoutfs: add inodes_since ioctl

2016-07-05 14:46:20 -07:00

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