linux-kernel - [PATCH 27/62] xarray: Add xa_get_entries and xa_get

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Date:   Wed, 22 Nov 2017 13:07:04 -0800
From:   Matthew Wilcox <willy@...radead.org>
To:     linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Cc:     Matthew Wilcox <mawilcox@...rosoft.com>
Subject: [PATCH 27/62] xarray: Add xa_get_entries and xa_get_tagged

From: Matthew Wilcox <mawilcox@...rosoft.com>

These functions allow a range of xarray entries to be extracted into a
compact normal array.

Signed-off-by: Matthew Wilcox <mawilcox@...rosoft.com>
---
 include/linux/xarray.h |  4 +++
 lib/xarray.c           | 69 ++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 73 insertions(+)

diff --git a/include/linux/xarray.h b/include/linux/xarray.h
index 427c792ddb2a..a48e7aa6406c 100644
--- a/include/linux/xarray.h
+++ b/include/linux/xarray.h
@@ -145,6 +145,10 @@ void *xa_clear_tag(struct xarray *, unsigned long index, xa_tag_t);
 
 void *xa_find(struct xarray *xa, unsigned long *index, unsigned long max);
 void *xa_next(struct xarray *xa, unsigned long *index, unsigned long max);
+int xa_get_entries(struct xarray *, void **dst, unsigned long start,
+			unsigned long max, unsigned int n);
+int xa_get_tagged(struct xarray *, void **dst, unsigned long start,
+			unsigned long max, unsigned int n, xa_tag_t);
 
 /**
  * xa_for_each() - Iterate over a portion of an XArray.
diff --git a/lib/xarray.c b/lib/xarray.c
index ea2dbd343380..9577a70495c0 100644
--- a/lib/xarray.c
+++ b/lib/xarray.c
@@ -1243,3 +1243,72 @@ void *xa_next(struct xarray *xa, unsigned long *indexp, unsigned long max)
 	return entry;
 }
 EXPORT_SYMBOL(xa_next);
+
+/**
+ * xa_get_entries() - Copy entries from the xarray into a normal array
+ * @xa: The source XArray to copy from
+ * @dst: The buffer to copy pointers into
+ * @start: The first index in the XArray eligible to be copied from
+ * @max: The last index in the XArray eligible to be copied from
+ * @n: The maximum number of entries to copy
+ *
+ * Return: The number of entries copied.
+ */
+int xa_get_entries(struct xarray *xa, void **dst, unsigned long start,
+			unsigned long max, unsigned int n)
+{
+	XA_STATE(xas, start);
+	void *entry;
+	unsigned int i = 0;
+
+	if (!n)
+		return 0;
+
+	rcu_read_lock();
+	xas_for_each(xa, &xas, entry, max) {
+		if (xas_retry(&xas, entry))
+			continue;
+		dst[i++] = entry;
+		if (i == n)
+			break;
+	}
+	rcu_read_unlock();
+
+	return i;
+}
+EXPORT_SYMBOL(xa_get_entries);
+
+/**
+ * xa_get_tagged() - Copy tagged entries from the xarray into a normal array.
+ * @xa: The source XArray to copy from.
+ * @dst: The buffer to copy pointers into.
+ * @start: The first index in the XArray eligible to be copied from.
+ * @max: The last index in the XArray eligible to be copied from
+ * @n: The maximum number of entries to copy.
+ * @tag: Tag number.
+ *
+ * Return: The number of entries copied.
+ */
+int xa_get_tagged(struct xarray *xa, void **dst, unsigned long start,
+			unsigned long max, unsigned int n, xa_tag_t tag)
+{
+	XA_STATE(xas, start);
+	void *entry;
+	unsigned int i = 0;
+
+	if (!n)
+		return 0;
+
+	rcu_read_lock();
+	xas_for_each_tag(xa, &xas, entry, max, tag) {
+		if (xas_retry(&xas, entry))
+			continue;
+		dst[i++] = entry;
+		if (i == n)
+			break;
+	}
+	rcu_read_unlock();
+
+	return i;
+}
+EXPORT_SYMBOL(xa_get_tagged);
-- 
2.15.0