linux-kernel - [PATCH 1/3] idr: add idr_prealloc

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Message-ID: <20251123063054.3502938-2-mjguzik@gmail.com>
Date: Sun, 23 Nov 2025 07:30:52 +0100
From: Mateusz Guzik <mjguzik@...il.com>
To: oleg@...hat.com
Cc: brauner@...nel.org,
	linux-kernel@...r.kernel.org,
	akpm@...ux-foundation.org,
	linux-mm@...ck.org,
	Mateusz Guzik <mjguzik@...il.com>
Subject: [PATCH 1/3] idr: add idr_prealloc_many

Signed-off-by: Mateusz Guzik <mjguzik@...il.com>
---
 include/linux/idr.h |  1 +
 lib/radix-tree.c    | 19 +++++++++++++++++--
 2 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/include/linux/idr.h b/include/linux/idr.h
index 789e23e67444..c9aeae695442 100644
--- a/include/linux/idr.h
+++ b/include/linux/idr.h
@@ -110,6 +110,7 @@ static inline void idr_set_cursor(struct idr *idr, unsigned int val)
 #define idr_unlock_irqrestore(idr, flags) \
 				xa_unlock_irqrestore(&(idr)->idr_rt, flags)
 
+void idr_preload_many(int nr, gfp_t gfp_mask);
 void idr_preload(gfp_t gfp_mask);
 
 int idr_alloc(struct idr *, void *ptr, int start, int end, gfp_t);
diff --git a/lib/radix-tree.c b/lib/radix-tree.c
index 976b9bd02a1b..2e71024e5323 100644
--- a/lib/radix-tree.c
+++ b/lib/radix-tree.c
@@ -1459,6 +1459,22 @@ int radix_tree_tagged(const struct radix_tree_root *root, unsigned int tag)
 }
 EXPORT_SYMBOL(radix_tree_tagged);
 
+/**
+ * idr_preload_many - preload for idr_alloc()
+ * @gfp_mask: allocation mask to use for preloading
+ * @nr: how many calls to preload for
+ *
+ * Preallocate memory to use for n calls to idr_alloc().  This function
+ * returns with preemption disabled.  It will be enabled by idr_preload_end().
+ */
+void idr_preload_many(int nr, gfp_t gfp_mask)
+{
+	WARN_ON_ONCE(!nr);
+	if (__radix_tree_preload(gfp_mask, nr * IDR_PRELOAD_SIZE))
+		local_lock(&radix_tree_preloads.lock);
+}
+EXPORT_SYMBOL(idr_preload_many);
+
 /**
  * idr_preload - preload for idr_alloc()
  * @gfp_mask: allocation mask to use for preloading
@@ -1468,8 +1484,7 @@ EXPORT_SYMBOL(radix_tree_tagged);
  */
 void idr_preload(gfp_t gfp_mask)
 {
-	if (__radix_tree_preload(gfp_mask, IDR_PRELOAD_SIZE))
-		local_lock(&radix_tree_preloads.lock);
+	idr_preload_many(1, gfp_mask);
 }
 EXPORT_SYMBOL(idr_preload);
 
-- 
2.48.1