From 64d3e9a9e0cc51957d243dd2b0adc5d74ff5e128 Mon Sep 17 00:00:00 2001 From: Matthew Wilcox Date: Fri, 1 Dec 2017 00:06:52 -0500 Subject: xarray: Step through an XArray The xas_next and xas_prev functions move the xas index by one position, and adjust the rest of the iterator state to match it. This is more efficient than calling xas_set() as it keeps the iterator at the leaves of the tree instead of walking the iterator from the root each time. Signed-off-by: Matthew Wilcox --- lib/xarray.c | 74 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 74 insertions(+) (limited to 'lib/xarray.c') diff --git a/lib/xarray.c b/lib/xarray.c index 057dbe0d3bf6..303c46579598 100644 --- a/lib/xarray.c +++ b/lib/xarray.c @@ -876,6 +876,80 @@ void xas_pause(struct xa_state *xas) } EXPORT_SYMBOL_GPL(xas_pause); +/* + * __xas_prev() - Find the previous entry in the XArray. + * @xas: XArray operation state. + * + * Helper function for xas_prev() which handles all the complex cases + * out of line. + */ +void *__xas_prev(struct xa_state *xas) +{ + void *entry; + + if (!xas_frozen(xas->xa_node)) + xas->xa_index--; + if (xas_not_node(xas->xa_node)) + return xas_load(xas); + + if (xas->xa_offset != get_offset(xas->xa_index, xas->xa_node)) + xas->xa_offset--; + + while (xas->xa_offset == 255) { + xas->xa_offset = xas->xa_node->offset - 1; + xas->xa_node = xa_parent(xas->xa, xas->xa_node); + if (!xas->xa_node) + return set_bounds(xas); + } + + for (;;) { + entry = xa_entry(xas->xa, xas->xa_node, xas->xa_offset); + if (!xa_is_node(entry)) + return entry; + + xas->xa_node = xa_to_node(entry); + xas_set_offset(xas); + } +} +EXPORT_SYMBOL_GPL(__xas_prev); + +/* + * __xas_next() - Find the next entry in the XArray. + * @xas: XArray operation state. + * + * Helper function for xas_next() which handles all the complex cases + * out of line. + */ +void *__xas_next(struct xa_state *xas) +{ + void *entry; + + if (!xas_frozen(xas->xa_node)) + xas->xa_index++; + if (xas_not_node(xas->xa_node)) + return xas_load(xas); + + if (xas->xa_offset != get_offset(xas->xa_index, xas->xa_node)) + xas->xa_offset++; + + while (xas->xa_offset == XA_CHUNK_SIZE) { + xas->xa_offset = xas->xa_node->offset + 1; + xas->xa_node = xa_parent(xas->xa, xas->xa_node); + if (!xas->xa_node) + return set_bounds(xas); + } + + for (;;) { + entry = xa_entry(xas->xa, xas->xa_node, xas->xa_offset); + if (!xa_is_node(entry)) + return entry; + + xas->xa_node = xa_to_node(entry); + xas_set_offset(xas); + } +} +EXPORT_SYMBOL_GPL(__xas_next); + /** * xas_find() - Find the next present entry in the XArray. * @xas: XArray operation state. -- cgit v1.2.3