Fix CPU hotplug

Allocate a kmem cache magazine for every possible CPU which might
be added to the system.  This ensures that when one of these CPUs
is enabled it can be safely used immediately.

For many systems the number of online CPUs is identical to the
number of present CPUs so this does imply an increased memory
footprint.  In fact, dynamically allocating the array of magazine
pointers instead of using the worst case NR_CPUS can end up
decreasing our memory footprint.

Signed-off-by: Brian Behlendorf <[email protected]>
Signed-off-by: Ned Bass <[email protected]>
Closes #482

1 files changed, 7 insertions, 8 deletions

diff --git a/module/spl/spl-kmem-cache.c b/module/spl/spl-kmem-cache.c
index a7f9ca3a5..5a8493fe4 100644
--- a/module/spl/spl-kmem-cache.c
+++ b/module/spl/spl-kmem-cache.c
@@ -805,15 +805,18 @@ spl_magazine_create(spl_kmem_cache_t *skc)
 	if (skc->skc_flags & KMC_NOMAGAZINE)
 		return (0);
 
+	skc->skc_mag = kzalloc(sizeof (spl_kmem_magazine_t *) *
+	    num_possible_cpus(), kmem_flags_convert(KM_SLEEP));
 	skc->skc_mag_size = spl_magazine_size(skc);
 	skc->skc_mag_refill = (skc->skc_mag_size + 1) / 2;
 
-	for_each_online_cpu(i) {
+	for_each_possible_cpu(i) {
 		skc->skc_mag[i] = spl_magazine_alloc(skc, i);
 		if (!skc->skc_mag[i]) {
 			for (i--; i >= 0; i--)
 				spl_magazine_free(skc->skc_mag[i]);
 
+			kfree(skc->skc_mag);
 			return (-ENOMEM);
 		}
 	}
@@ -833,11 +836,13 @@ spl_magazine_destroy(spl_kmem_cache_t *skc)
 	if (skc->skc_flags & KMC_NOMAGAZINE)
 		return;
 
-	for_each_online_cpu(i) {
+	for_each_possible_cpu(i) {
 		skm = skc->skc_mag[i];
 		spl_cache_flush(skc, skm, skm->skm_avail);
 		spl_magazine_free(skm);
 	}
+
+	kfree(skc->skc_mag);
 }
 
 /*
@@ -880,12 +885,6 @@ spl_kmem_cache_create(char *name, size_t size, size_t align,
 
 	might_sleep();
 
-	/*
-	 * Allocate memory for a new cache and initialize it.  Unfortunately,
-	 * this usually ends up being a large allocation of ~32k because
-	 * we need to allocate enough memory for the worst case number of
-	 * cpus in the magazine, skc_mag[NR_CPUS].
-	 */
 	skc = kzalloc(sizeof (*skc), lflags);
 	if (skc == NULL)
 		return (NULL);