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Message-Id: <20171215220450.7899-17-willy@infradead.org>
Date: Fri, 15 Dec 2017 14:03:48 -0800
From: Matthew Wilcox <willy@...radead.org>
To: linux-kernel@...r.kernel.org
Cc: Matthew Wilcox <mawilcox@...rosoft.com>,
Ross Zwisler <ross.zwisler@...ux.intel.com>,
David Howells <dhowells@...hat.com>,
Shaohua Li <shli@...nel.org>, Jens Axboe <axboe@...nel.dk>,
Rehas Sachdeva <aquannie@...il.com>,
Marc Zyngier <marc.zyngier@....com>, linux-mm@...ck.org,
linux-fsdevel@...r.kernel.org,
linux-f2fs-devel@...ts.sourceforge.net,
linux-nilfs@...r.kernel.org, linux-btrfs@...r.kernel.org,
linux-xfs@...r.kernel.org, linux-usb@...r.kernel.org,
linux-raid@...r.kernel.org
Subject: [PATCH v5 16/78] xarray: Add xa_get_entries, xa_get_tagged and xa_get_maybe_tag
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 | 27 ++++++++++++++++
lib/xarray.c | 88 ++++++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 115 insertions(+)
diff --git a/include/linux/xarray.h b/include/linux/xarray.h
index 85a319463e46..1367d694eebd 100644
--- a/include/linux/xarray.h
+++ b/include/linux/xarray.h
@@ -140,6 +140,33 @@ 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_find_after(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_get_maybe_tag() - 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.
+ * @tag: Tag number.
+ *
+ * If you specify %XA_NO_TAG as the tag number, this is the same as
+ * xa_get_entries(). Otherwise, it is the same as xa_get_tagged().
+ *
+ * Return: The number of entries copied.
+ */
+static inline int xa_get_maybe_tag(struct xarray *xa, void **dst,
+ unsigned long start, unsigned long max,
+ unsigned int n, xa_tag_t tag)
+{
+ if (tag == XA_NO_TAG)
+ return xa_get_entries(xa, dst, start, max, n);
+ return xa_get_tagged(xa, dst, start, max, n, tag);
+}
/**
* xa_for_each() - Iterate over a portion of an XArray.
diff --git a/lib/xarray.c b/lib/xarray.c
index 9ac1e9730c24..e73ae7b57fc9 100644
--- a/lib/xarray.c
+++ b/lib/xarray.c
@@ -1330,6 +1330,94 @@ void *xa_find_after(struct xarray *xa, unsigned long *indexp, unsigned long max)
}
EXPORT_SYMBOL(xa_find_after);
+/**
+ * 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.
+ *
+ * Copies up to @n non-NULL entries from the XArray. The copied entries will
+ * have indices between @start and @max, inclusive.
+ *
+ * This function uses the RCU lock to protect itself. That means that the
+ * entries returned may not represent a snapshot of the XArray at a moment
+ * in time. For example, if index 5 is stored to, then index 10 is stored to,
+ * calling xa_get_entries() 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.
+ *
+ * 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, xa, start);
+ void *entry;
+ unsigned int i = 0;
+
+ if (!n)
+ return 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;
+}
+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.
+ *
+ * Copies up to @n non-NULL entries that have @tag set from the XArray. The
+ * copied entries will have indices between @start and @max, inclusive.
+ *
+ * See the xa_get_entries() documentation for the consistency guarantees
+ * provided.
+ *
+ * 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, xa, start);
+ void *entry;
+ unsigned int i = 0;
+
+ if (!n)
+ return 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;
+}
+EXPORT_SYMBOL(xa_get_tagged);
+
#ifdef XA_DEBUG
void xa_dump_node(const struct xa_node *node)
{
--
2.15.1
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