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From: Matthew Wilcox <>
To: Andrew Morton <>
	Rasmus Villemoes <>,
	Daniel Vetter <>, Tejun Heo <>
Subject: [PATCH] ida: Remove simple_ida_lock
Date: Sat, 31 Mar 2018 05:53:32 -0700
Message-ID: <> (raw)

From: Matthew Wilcox <>

Improve the scalability of the IDA by using the per-IDA xa_lock rather
than the global simple_ida_lock.  IDAs are not typically used in
performance-sensitive locations, but since we have this lock anyway,
we can use it.  It is also a step towards converting the IDA from the
radix tree to the XArray.

Signed-off-by: Matthew Wilcox <>
 lib/idr.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/lib/idr.c b/lib/idr.c
index b2f7ab31ce55..e80da084117c 100644
--- a/lib/idr.c
+++ b/lib/idr.c
@@ -7,7 +7,6 @@
 #include <linux/xarray.h>
 DEFINE_PER_CPU(struct ida_bitmap *, ida_bitmap);
-static DEFINE_SPINLOCK(simple_ida_lock);
  * idr_alloc_u32() - Allocate an ID.
@@ -572,7 +571,7 @@ int ida_simple_get(struct ida *ida, unsigned int start, unsigned int end,
 	if (!ida_pre_get(ida, gfp_mask))
 		return -ENOMEM;
-	spin_lock_irqsave(&simple_ida_lock, flags);
+	xa_lock_irqsave(&ida->ida_rt, flags);
 	ret = ida_get_new_above(ida, start, &id);
 	if (!ret) {
 		if (id > max) {
@@ -582,7 +581,7 @@ int ida_simple_get(struct ida *ida, unsigned int start, unsigned int end,
 			ret = id;
-	spin_unlock_irqrestore(&simple_ida_lock, flags);
+	xa_unlock_irqrestore(&ida->ida_rt, flags);
 	if (unlikely(ret == -EAGAIN))
 		goto again;
@@ -606,8 +605,8 @@ void ida_simple_remove(struct ida *ida, unsigned int id)
 	unsigned long flags;
 	BUG_ON((int)id < 0);
-	spin_lock_irqsave(&simple_ida_lock, flags);
+	xa_lock_irqsave(&ida->ida_rt, flags);
 	ida_remove(ida, id);
-	spin_unlock_irqrestore(&simple_ida_lock, flags);
+	xa_unlock_irqrestore(&ida->ida_rt, flags);

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