ida: Move ida_bitmap to a percpu variable

When we preload the IDA, we allocate an IDA bitmap.  Instead of storing
that preallocated bitmap in the IDA, we store it in a percpu variable.
Generally there are more IDAs in the system than CPUs, so this cuts down
on the number of preallocated bitmaps that are unused, and about half
of the IDA users did not call ida_destroy() so they were leaking IDA
bitmaps.

Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>

1 files changed, 2 insertions, 37 deletions

diff --git a/lib/idr.c b/lib/idr.c
index b87056e2cc4c..2abd7769c430 100644
--- a/lib/idr.c
+++ b/lib/idr.c
@@ -4,6 +4,7 @@
 #include <linux/slab.h>
 #include <linux/spinlock.h>
 
+DEFINE_PER_CPU(struct ida_bitmap *, ida_bitmap);
 static DEFINE_SPINLOCK(simple_ida_lock);
 
 /**
@@ -193,38 +194,6 @@ EXPORT_SYMBOL(idr_replace);
  * limitation, it should be quite straightforward to raise the maximum.
  */
 
-/**
- * ida_pre_get - reserve resources for ida allocation
- * @ida: ida handle
- * @gfp: memory allocation flags
- *
- * This function should be called before calling ida_get_new_above().  If it
- * is unable to allocate memory, it will return %0.  On success, it returns %1.
- */
-int ida_pre_get(struct ida *ida, gfp_t gfp)
-{
-	struct ida_bitmap *bitmap;
-
-	/*
-	 * This looks weird, but the IDA API has no preload_end() equivalent.
-	 * Instead, ida_get_new() can return -EAGAIN, prompting the caller
-	 * to return to the ida_pre_get() step.
-	 */
-	idr_preload(gfp);
-	idr_preload_end();
-
-	if (!ida->free_bitmap) {
-		bitmap = kmalloc(sizeof(struct ida_bitmap), gfp);
-		if (!bitmap)
-			return 0;
-		bitmap = xchg(&ida->free_bitmap, bitmap);
-		kfree(bitmap);
-	}
-
-	return 1;
-}
-EXPORT_SYMBOL(ida_pre_get);
-
 #define IDA_MAX (0x80000000U / IDA_BITMAP_BITS)
 
 /**
@@ -292,10 +261,9 @@ int ida_get_new_above(struct ida *ida, int start, int *id)
 			new += bit;
 			if (new < 0)
 				return -ENOSPC;
-			bitmap = ida->free_bitmap;
+			bitmap = this_cpu_xchg(ida_bitmap, NULL);
 			if (!bitmap)
 				return -EAGAIN;
-			ida->free_bitmap = NULL;
 			memset(bitmap, 0, sizeof(*bitmap));
 			__set_bit(bit, bitmap->bitmap);
 			radix_tree_iter_replace(root, &iter, slot, bitmap);
@@ -361,9 +329,6 @@ void ida_destroy(struct ida *ida)
 		kfree(bitmap);
 		radix_tree_iter_delete(&ida->ida_rt, &iter, slot);
 	}
-
-	kfree(ida->free_bitmap);
-	ida->free_bitmap = NULL;
 }
 EXPORT_SYMBOL(ida_destroy);