linux-kernel - [PATCH 1/3] xarray: add xa

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Message-ID: <20240812063143.3806677-2-hch@lst.de>
Date: Mon, 12 Aug 2024 08:31:00 +0200
From: Christoph Hellwig <hch@....de>
To: Chandan Babu R <chandan.babu@...cle.com>,
	Matthew Wilcox <willy@...radead.org>
Cc: "Darrick J. Wong" <djwong@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-xfs@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-fsdevel@...r.kernel.org
Subject: [PATCH 1/3] xarray: add xa_set

Add a convenience wrapper or xa_store that returns an error value when
there is an existing entry instead of the old entry.  This simplifies
code that wants to check that it is never overwriting an existing
entry.

Signed-off-by: Christoph Hellwig <hch@....de>
---
 include/linux/xarray.h |  1 +
 lib/xarray.c           | 33 +++++++++++++++++++++++++++++++++
 2 files changed, 34 insertions(+)

diff --git a/include/linux/xarray.h b/include/linux/xarray.h
index 0b618ec04115fc..8dc4e575378ca5 100644
--- a/include/linux/xarray.h
+++ b/include/linux/xarray.h
@@ -354,6 +354,7 @@ struct xarray {
 
 void *xa_load(struct xarray *, unsigned long index);
 void *xa_store(struct xarray *, unsigned long index, void *entry, gfp_t);
+int xa_set(struct xarray *, unsigned long index, void *entry, gfp_t);
 void *xa_erase(struct xarray *, unsigned long index);
 void *xa_store_range(struct xarray *, unsigned long first, unsigned long last,
 			void *entry, gfp_t);
diff --git a/lib/xarray.c b/lib/xarray.c
index 32d4bac8c94ca1..500d3405c0c8c0 100644
--- a/lib/xarray.c
+++ b/lib/xarray.c
@@ -1600,6 +1600,39 @@ void *xa_store(struct xarray *xa, unsigned long index, void *entry, gfp_t gfp)
 }
 EXPORT_SYMBOL(xa_store);
 
+/**
+ * xa_set() - Store this entry in the XArray.
+ * @xa: XArray.
+ * @index: Index into array.
+ * @entry: New entry.
+ * @gfp: Memory allocation flags.
+ *
+ * After this function returns, loads from this index will return @entry.
+ * Storing into an existing multi-index entry updates the entry of every index.
+ * The marks associated with @index are unaffected unless @entry is %NULL.
+ *
+ * Context: Any context.  Takes and releases the xa_lock.
+ * May sleep if the @gfp flags permit.
+ * Return: 0 on success, -EEXIST if there already is an entry at @index, -EINVAL
+ * if @entry cannot be stored in an XArray, or -ENOMEM if memory allocation
+ * failed.
+ */
+int xa_set(struct xarray *xa, unsigned long index, void *entry, gfp_t gfp)
+{
+	int error = 0;
+	void *curr;
+
+	curr = xa_store(xa, index, entry, gfp);
+	if (curr) {
+		error = xa_err(curr);
+		if (error == 0)
+			error = -ENOENT;
+	}
+
+	return error;
+}
+EXPORT_SYMBOL(xa_set);
+
 /**
  * __xa_cmpxchg() - Store this entry in the XArray.
  * @xa: XArray.
-- 
2.43.0