Changes

== Stacked images ==

== Stacked images ==

When you do [[incremental dumps]] there appear the <code>parent</code> symlink and images with pages become dependant on each other.

When [[incremental dumps]] are performed, for every iteration a <code>parent</code> symlink is created, and images become dependent on their respective parent(s).

There appears the 3rd field in the pagemap, called <code>in_parent</code>. When set this boolean value means, that the respective data for the pagemap should be found in the parent images. While searching for data in parent the same algorithm is used -- first the pagemap is resolved, then the data is found in pages. For parent images, the data (either complete or partial) can also be found in ''its'' parent images.  

There appears the 3rd field in the pagemap, called <code>in_parent</code>. It is a boolean flag, when set, means the respective data for the given pagemap is available from a parent image. While searching for data in parent, the same algorithm is used -- first the pagemap is resolved, then the data is found in pages. For parent images, the data (either complete or partial) can also be found in ''its'' parent images.  

Respectively, the bottom image (with no parent link) should have no in_parent bits at all.

Naturally, the bottom image (the one with no parent link) must have no <code>in_parent</code> bits set.

=== Example ===

=== Example ===

Let's take another example, consider we have pagemap from previous example with one in_parent bit:

Consider we have a pagemap from the previous example with <code>in_parent</code> bit set for one entry:

<pre>

<pre>

</pre>

</pre>

In this case the pages image would be only 32k in size, since the first 4 pages should be found in the parent. Thus the parent pagemap image should container one ore more pagemaps that cover the <code>0x1000000 ... 0x1004000</code> area, for example like this

In this case, the pages image would be only 32k in size, since the first 4 pages are to be found in the parent. Thus the parent pagemap image should container one or more pagemaps covering the <code>0x1000000 ... 0x1004000</code> area, for example, like this

<pre>

<pre>

</pre>

</pre>

This, in turn, would mean that first 2 pages from this range are in parent's pages image file and the last 2 should be looked up deeper -- in the grand-parent pagemaps.

This, in turn, means that the first 2 pages from this range are available from the parent pages image file, and the last 2 should be looked up deeper, i.e. in the grand-parent pagemaps.

== Deduplication ==

== Deduplication ==