Docs/admin-guide/mm/zswap: s/red-black tree/xarray/

The change from commit 796c2c23e14e ("zswap: replace RB tree with xarray")
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Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: SeongJae Park <[e-mail]>
Acked-by: Yosry Ahmed <[e-mail]>
Acked-by: Nhat Pham <[e-mail]>
Reviewed-by: Chengming Zhou <[e-mail]>
Cc: Chris Li <[e-mail]>
Cc: David Hildenbrand <[e-mail]>
Cc: Johannes Weiner <[e-mail]>
Cc: Jonathan Corbet <[e-mail]>
Cc: Liam Howlett <[e-mail]>
Cc: Lorenzo Stoakes <[e-mail]>
Cc: Michal Hocko <[e-mail]>
Cc: Mike Rapoport <[e-mail]>
Cc: Muchun Song <[e-mail]>
Cc: Roman Gushchin <[e-mail]>
Cc: Shakeel Butt <[e-mail]>
Cc: Suren Baghdasaryan <[e-mail]>
Cc: Vlastimil Babka <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>

Documentation/admin-guide/mm/zswap.rst

···
 accessed.  The compressed memory pool grows on demand and shrinks as compressed
 pages are freed.  The pool is not preallocated.
 
-When a swap page is passed from swapout to zswap, zswap maintains a mapping
-of the swap entry, a combination of the swap type and swap offset, to the
-zsmalloc handle that references that compressed swap page.  This mapping is
-achieved with a red-black tree per swap type.  The swap offset is the search
-key for the tree nodes.
+When a swap page is passed from swapout to zswap, zswap maintains a mapping of
+the swap entry, a combination of the swap type and swap offset, to the zsmalloc
+handle that references that compressed swap page.  This mapping is achieved
+with an xarray per swap type.  The swap offset is the search key for the xarray
+nodes.
 
 During a page fault on a PTE that is a swap entry, the swapin code calls the
 zswap load function to decompress the page into the page allocated by the page