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Subject[PATCH v9 19/61] xarray: Add xa_extract
Date
From: Matthew Wilcox <mawilcox@microsoft.com>

This function combines the functionality of radix_tree_gang_lookup() and
radix_tree_gang_lookup_tagged(). It extracts entries matching the
specified filter into a normal array.

Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
---
include/linux/xarray.h | 2 ++
lib/xarray.c | 80 ++++++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 82 insertions(+)

diff --git a/include/linux/xarray.h b/include/linux/xarray.h
index cf7966bfdd3e..85dd909586f0 100644
--- a/include/linux/xarray.h
+++ b/include/linux/xarray.h
@@ -227,6 +227,8 @@ void *xa_find(struct xarray *xa, unsigned long *index,
unsigned long max, xa_tag_t) __attribute__((nonnull(2)));
void *xa_find_after(struct xarray *xa, unsigned long *index,
unsigned long max, xa_tag_t) __attribute__((nonnull(2)));
+unsigned int xa_extract(struct xarray *, void **dst, unsigned long start,
+ unsigned long max, unsigned int n, xa_tag_t);

/**
* xa_init() - Initialise an empty XArray.
diff --git a/lib/xarray.c b/lib/xarray.c
index 267510e98a57..124bbfec66ae 100644
--- a/lib/xarray.c
+++ b/lib/xarray.c
@@ -1388,6 +1388,86 @@ void *xa_find_after(struct xarray *xa, unsigned long *indexp,
}
EXPORT_SYMBOL(xa_find_after);

+static unsigned int xas_extract_present(struct xa_state *xas, void **dst,
+ unsigned long max, unsigned int n)
+{
+ void *entry;
+ unsigned int i = 0;
+
+ rcu_read_lock();
+ xas_for_each(xas, entry, max) {
+ if (xas_retry(xas, entry))
+ continue;
+ dst[i++] = entry;
+ if (i == n)
+ break;
+ }
+ rcu_read_unlock();
+
+ return i;
+}
+
+static unsigned int xas_extract_tag(struct xa_state *xas, void **dst,
+ unsigned long max, unsigned int n, xa_tag_t tag)
+{
+ void *entry;
+ unsigned int i = 0;
+
+ rcu_read_lock();
+ xas_for_each_tag(xas, entry, max, tag) {
+ if (xas_retry(xas, entry))
+ continue;
+ dst[i++] = entry;
+ if (i == n)
+ break;
+ }
+ rcu_read_unlock();
+
+ return i;
+}
+
+/**
+ * xa_extract() - Copy selected entries from the XArray into a normal array.
+ * @xa: The source XArray to copy from.
+ * @dst: The buffer to copy entries into.
+ * @start: The first index in the XArray eligible to be selected.
+ * @max: The last index in the XArray eligible to be selected.
+ * @n: The maximum number of entries to copy.
+ * @filter: Selection criterion.
+ *
+ * Copies up to @n entries that match @filter from the XArray. The
+ * copied entries will have indices between @start and @max, inclusive.
+ *
+ * The @filter may be an XArray tag value, in which case entries which are
+ * tagged with that tag will be copied. It may also be %XA_PRESENT, in
+ * which case non-NULL entries will be copied.
+ *
+ * The entries returned may not represent a snapshot of the XArray at a
+ * moment in time. For example, if another thread stores to index 5, then
+ * index 10, calling xa_extract() may return the old contents of index 5
+ * and the new contents of index 10. Indices not modified while this
+ * function is running will not be skipped.
+ *
+ * If you need stronger guarantees, holding the xa_lock across calls to this
+ * function will prevent concurrent modification.
+ *
+ * Context: Any context. Takes and releases the RCU lock.
+ * Return: The number of entries copied.
+ */
+unsigned int xa_extract(struct xarray *xa, void **dst, unsigned long start,
+ unsigned long max, unsigned int n, xa_tag_t filter)
+{
+ XA_STATE(xas, xa, start);
+
+ if (!n)
+ return 0;
+
+ if ((__force unsigned int)filter < XA_MAX_TAGS)
+ return xas_extract_tag(&xas, dst, max, n, filter);
+ return xas_extract_present(&xas, dst, max, n);
+}
+EXPORT_SYMBOL(xa_extract);
+
#ifdef XA_DEBUG
void xa_dump_node(const struct xa_node *node)
{
--
2.16.1
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