Re: [PATCH 1/2 v6] mm/mempolicy: Weighted Interleave Auto-tuning

yunjeong.mun
2025-02-28T00:16:43Z

On Wed, 26 Feb 2025 13:35:17 -0800 Joshua Hahn <joshua.hahnjy@gmail.com> wrote:
> On machines with multiple memory nodes, interleaving page allocations
> across nodes allows for better utilization of each node's bandwidth.
> Previous work by Gregory Price [1] introduced weighted interleave, which
> allowed for pages to be allocated across nodes according to user-set ratios.
>
> Ideally, these weights should be proportional to their bandwidth, so
> that under bandwidth pressure, each node uses its maximal efficient
> bandwidth and prevents latency from increasing exponentially.
>
> Previously, weighted interleave's default weights were just 1s -- which
> would be equivalent to the (unweighted) interleave mempolicy, which goes
> through the nodes in a round-robin fashion, ignoring bandwidth information.
>
> This patch has two main goals:
> First, it makes weighted interleave easier to use for users who wish to
> relieve bandwidth pressure when using nodes with varying bandwidth (CXL).
> By providing a set of "real" default weights that just work out of the
> box, users who might not have the capability (or wish to) perform
> experimentation to find the most optimal weights for their system can
> still take advantage of bandwidth-informed weighted interleave.
>
> Second, it allows for weighted interleave to dynamically adjust to
> hotplugged memory with new bandwidth information. Instead of manually
> updating node weights every time new bandwidth information is reported
> or taken off, weighted interleave adjusts and provides a new set of
> default weights for weighted interleave to use when there is a change
> in bandwidth information.
>
> To meet these goals, this patch introduces an auto-configuration mode
> for the interleave weights that provides a reasonable set of default
> weights, calculated using bandwidth data reported by the system. In auto
> mode, weights are dynamically adjusted based on whatever the current
> bandwidth information reports (and responds to hotplug events).
>
> This patch still supports users manually writing weights into the nodeN
> sysfs interface by entering into manual mode. When a user enters manual
> mode, the system stops dynamically updating any of the node weights,
> even during hotplug events that shift the optimal weight distribution.
>
> A new sysfs interface "auto" is introduced, which allows users to switch
> between the auto (writing 1 or Y) and manual (writing 0 or N) modes. The
> system also automatically enters manual mode when a nodeN interface is
> manually written to.
>
> There is one functional change that this patch makes to the existing
> weighted_interleave ABI: previously, writing 0 directly to a nodeN
> interface was said to reset the weight to the system default. Before
> this patch, the default for all weights were 1, which meant that writing
> 0 and 1 were functionally equivalent.
>
> [1] https://lore.kernel.org/linux-mm/20240202170238.90004-1-gregory.price@memverge.com/
>
> Signed-off-by: Joshua Hahn <joshua.hahnjy@gmail.com>
> Co-developed-by: Gregory Price <gourry@gourry.net>
> Signed-off-by: Gregory Price <gourry@gourry.net>
> Reviewed-by: Harry Yoo <harry.yoo@oracle.com>
> ---
> Changelog
> v6:
> - iw_weights and mode_auto are combined into one rcu-protected struct.
> - Protection against memoryless nodes, as suggested by Oscar Salvador
> - Wordsmithing (documentation, commit message and comments), as suggested
> by Andrew Morton.
> - Removed unnecessary #include statement in hmat.c, as pointed out by
> Harry (Hyeonggon) Yoo and Ying Huang.
> - Bandwidth values changed from u64_t to unsigned int, as pointed out by
> Ying Huang and Dan Carpenter.
> - RCU optimizations, as suggested by Ying Huang.
> - A second patch is included to fix unintended behavior that creates a
> weight knob for memoryless nodes as well.
> - Sysfs show/store functions use str_true_false & kstrtobool.
> - Fix a build error in 32-bit systems, which are unable to perform
> 64-bit division by casting 64-bit values to 32-bit, if under the range.
>
> v5:
> - I accidentally forgot to add the mm/mempolicy: subject tag since v1 of
> this patch. Added to the subject now!
> - Wordsmithing, correcting typos, and re-naming variables for clarity.
> - No functional changes.
>
> v4:
> - Renamed the mode interface to the "auto" interface, which now only
> emits either 'Y' or 'N'. Users can now interact with it by
> writing 'Y', '1', 'N', or '0' to it.
> - Added additional documentation to the nodeN sysfs interface.
> - Makes sure iw_table locks are properly held.
> - Removed unlikely() call in reduce_interleave_weights.
> - Wordsmithing
>
> v3:
> - Weightiness (max_node_weight) is now fixed to 32.
> - Instead, the sysfs interface now exposes a "mode" parameter, which
> can either be "auto" or "manual".
> - Thank you Hyeonggon and Honggyu for the feedback.
> - Documentation updated to reflect new sysfs interface, explicitly
> specifies that 0 is invalid.
> - Thank you Gregory and Ying for the discussion on how best to
> handle the 0 case.
> - Re-worked nodeN sysfs store to handle auto --> manual shifts
> - mempolicy_set_node_perf internally handles the auto / manual
> case differently now. bw is always updated, iw updates depend on
> what mode the user is in.
> - Wordsmithing comments for clarity.
> - Removed RFC tag.
>
> v2:
> - Name of the interface is changed: "max_node_weight" --> "weightiness"
> - Default interleave weight table no longer exists. Rather, the
> interleave weight table is initialized with the defaults, if bandwidth
> information is available.
> - In addition, all sections that handle iw_table have been changed
> to reference iw_table if it exists, otherwise defaulting to 1.
> - All instances of unsigned long are converted to uint64_t to guarantee
> support for both 32-bit and 64-bit machines
> - sysfs initialization cleanup
> - Documentation has been rewritten to explicitly outline expected
> behavior and expand on the interpretation of "weightiness".
> - kzalloc replaced with kcalloc for readability
> - Thank you Gregory and Hyeonggon for your review & feedback!
>
> ...fs-kernel-mm-mempolicy-weighted-interleave | 34 +-
> drivers/base/node.c | 9 +
> include/linux/mempolicy.h | 9 +
> mm/mempolicy.c | 323 +++++++++++++++---
> 4 files changed, 322 insertions(+), 53 deletions(-)
>
> diff --git a/Documentation/ABI/testing/sysfs-kernel-mm-mempolicy-weighted-interleave b/Documentation/ABI/testing/sysfs-kernel-mm-mempolicy-weighted-interleave
> index 0b7972de04e9..862b19943a85 100644
> --- a/Documentation/ABI/testing/sysfs-kernel-mm-mempolicy-weighted-interleave
> +++ b/Documentation/ABI/testing/sysfs-kernel-mm-mempolicy-weighted-interleave
> @@ -20,6 +20,34 @@ Description: Weight configuration interface for nodeN
> Minimum weight: 1
> Maximum weight: 255
>
> - Writing an empty string or `0` will reset the weight to the
> - system default. The system default may be set by the kernel
> - or drivers at boot or during hotplug events.
> + Writing invalid values (i.e. any values not in [1,255],
> + empty string, ...) will return -EINVAL.
> +
> + Changing the weight to a valid value will automatically
> + update the system to manual mode as well.
> +
> +What: /sys/kernel/mm/mempolicy/weighted_interleave/auto
> +Date: February 2025
> +Contact: Linux memory management mailing list <linux-mm@kvack.org>
> +Description: Auto-weighting configuration interface
> +
> + Configuration mode for weighted interleave. A 'Y' indicates
> + that the system is in auto mode, and a 'N' indicates that
> + the system is in manual mode. All other values are invalid.
> +
> + In auto mode, all node weights are re-calculated and overwritten
> + (visible via the nodeN interfaces) whenever new bandwidth data
> + is made available during either boot or hotplug events.
> +
> + In manual mode, node weights can only be updated by the user.
> + Note that nodes that are onlined with previously set weights
> + will inherit those weights. If they were not previously set or
> + are onlined with missing bandwidth data, the weights will use
> + a default weight of 1.
> +
> + Writing Y or 1 to the interface will enable auto mode, while
> + writing N or 0 will enable manual mode. All other strings will
> + be ignored, and -EINVAL will be returned.
> +
> + Writing a new weight to a node directly via the nodeN interface
> + will also automatically update the system to manual mode.
> diff --git a/drivers/base/node.c b/drivers/base/node.c
> index 0ea653fa3433..f3c01fb90db1 100644
> --- a/drivers/base/node.c
> +++ b/drivers/base/node.c
> @@ -7,6 +7,7 @@
> #include <linux/init.h>
> #include <linux/mm.h>
> #include <linux/memory.h>
> +#include <linux/mempolicy.h>
> #include <linux/vmstat.h>
> #include <linux/notifier.h>
> #include <linux/node.h>
> @@ -214,6 +215,14 @@ void node_set_perf_attrs(unsigned int nid, struct access_coordinate *coord,
> break;
> }
> }
> +
> + /* When setting CPU access coordinates, update mempolicy */
> + if (access == ACCESS_COORDINATE_CPU) {
> + if (mempolicy_set_node_perf(nid, coord)) {
> + pr_info("failed to set mempolicy attrs for node %d\n",
> + nid);
> + }
> + }
> }
> EXPORT_SYMBOL_GPL(node_set_perf_attrs);
>
> diff --git a/include/linux/mempolicy.h b/include/linux/mempolicy.h
> index ce9885e0178a..78f1299bdd42 100644
> --- a/include/linux/mempolicy.h
> +++ b/include/linux/mempolicy.h
> @@ -11,6 +11,7 @@
> #include <linux/slab.h>
> #include <linux/rbtree.h>
> #include <linux/spinlock.h>
> +#include <linux/node.h>
> #include <linux/nodemask.h>
> #include <linux/pagemap.h>
> #include <uapi/linux/mempolicy.h>
> @@ -56,6 +57,11 @@ struct mempolicy {
> } w;
> };
>
> +struct weighted_interleave_state {
> + bool mode_auto;
> + u8 iw_table[]; /* A null iw_table is interpreted as an array of 1s. */
> +};
> +
> /*
> * Support for managing mempolicy data objects (clone, copy, destroy)
> * The default fast path of a NULL MPOL_DEFAULT policy is always inlined.
> @@ -178,6 +184,9 @@ static inline bool mpol_is_preferred_many(struct mempolicy *pol)
>
> extern bool apply_policy_zone(struct mempolicy *policy, enum zone_type zone);
>
> +extern int mempolicy_set_node_perf(unsigned int node,
> + struct access_coordinate *coords);
> +
> #else
>
> struct mempolicy {};
> diff --git a/mm/mempolicy.c b/mm/mempolicy.c
> index bbaadbeeb291..4cc04ff8f12c 100644
> --- a/mm/mempolicy.c
> +++ b/mm/mempolicy.c
> @@ -109,6 +109,7 @@
> #include <linux/mmu_notifier.h>
> #include <linux/printk.h>
> #include <linux/swapops.h>
> +#include <linux/gcd.h>
>
> #include <asm/tlbflush.h>
> #include <asm/tlb.h>
> @@ -139,31 +140,151 @@ static struct mempolicy default_policy = {
> static struct mempolicy preferred_node_policy[MAX_NUMNODES];
>
> /*
> - * iw_table is the sysfs-set interleave weight table, a value of 0 denotes
> - * system-default value should be used. A NULL iw_table also denotes that
> - * system-default values should be used. Until the system-default table
> - * is implemented, the system-default is always 1.
> - *
> - * iw_table is RCU protected
> + * weightiness balances the tradeoff between small weights (cycles through nodes
> + * faster, more fair/even distribution) and large weights (smaller errors
> + * between actual bandwidth ratios and weight ratios). 32 is a number that has
> + * been found to perform at a reasonable compromise between the two goals.
> + */
> +static const int weightiness = 32;
> +
> +/* wi_state is RCU protected */
> +static struct weighted_interleave_state __rcu *wi_state;
> +static unsigned int *node_bw_table;
> +
> +/*
> + * iw_table_lock protects both wi_state and node_bw_table.
> + * node_bw_table is only used by writers to update wi_state.
> */
> -static u8 __rcu *iw_table;
> static DEFINE_MUTEX(iw_table_lock);
>
> static u8 get_il_weight(int node)
> {
> - u8 *table;
> - u8 weight;
> + u8 weight = 1;
>
> rcu_read_lock();
> - table = rcu_dereference(iw_table);
> - /* if no iw_table, use system default */
> - weight = table ? table[node] : 1;
> - /* if value in iw_table is 0, use system default */
> - weight = weight ? weight : 1;
> + if (rcu_access_pointer(wi_state))
> + weight = rcu_dereference(wi_state)->iw_table[node];
> rcu_read_unlock();
> +
> return weight;
> }
>
> +/*
> + * Convert bandwidth values into weighted interleave weights.
> + * Call with iw_table_lock.
> + */
> +static void reduce_interleave_weights(unsigned int *bw, u8 *new_iw)
> +{
> + u64 sum_bw = 0;
> + unsigned int cast_sum_bw, sum_iw = 0;
> + unsigned int scaling_factor = 1, iw_gcd = 1;
> + int nid;
> +
> + /* Recalculate the bandwidth distribution given the new info */
> + for_each_node_state(nid, N_MEMORY)
> + sum_bw += bw[nid];
> +
> + for (nid = 0; nid < nr_node_ids; nid++) {
> + /* Set memoryless nodes' weights to 1 to prevent div/0 later */
> + if (!node_state(nid, N_MEMORY)) {
> + new_iw[nid] = 1;
> + continue;
> + }
> +
> + scaling_factor = 100 * bw[nid];
> +
> + /*
> + * Try not to perform 64-bit division.
> + * If sum_bw < scaling_factor, then sum_bw < U32_MAX.
> + * If sum_bw > scaling_factor, then bw[nid] is less than
> + * 1% of the total bandwidth. Round up to 1%.
> + */
> + if (bw[nid] && sum_bw < scaling_factor) {
> + cast_sum_bw = (unsigned int)sum_bw;
> + new_iw[nid] = scaling_factor / cast_sum_bw;
> + } else {
> + new_iw[nid] = 1;
> + }
> + sum_iw += new_iw[nid];
> + }
> +
> + /*
> + * Scale each node's share of the total bandwidth from percentages
> + * to whole numbers in the range [1, weightiness]
> + */
> + for_each_node_state(nid, N_MEMORY) {
> + scaling_factor = weightiness * new_iw[nid];
> + new_iw[nid] = max(scaling_factor / sum_iw, 1);
> + if (nid == 0)
> + iw_gcd = new_iw[0];
> + iw_gcd = gcd(iw_gcd, new_iw[nid]);
> + }
> +
> + /* 1:2 is strictly better than 16:32. Reduce by the weights' GCD. */
> + for_each_node_state(nid, N_MEMORY)
> + new_iw[nid] /= iw_gcd;
> +}
> +
> +int mempolicy_set_node_perf(unsigned int node, struct access_coordinate *coords)
> +{
> + struct weighted_interleave_state *new_wi_state, *old_wi_state = NULL;
> + unsigned int *old_bw, *new_bw;
> + unsigned int bw_val;
> +
> + bw_val = min(coords->read_bandwidth, coords->write_bandwidth);
> + new_bw = kcalloc(nr_node_ids, sizeof(unsigned int), GFP_KERNEL);
> + if (!new_bw)
> + return -ENOMEM;
> +
> + new_wi_state = kzalloc(struct_size(new_wi_state, iw_table, nr_node_ids),
> + GFP_KERNEL);
> + if (!new_wi_state) {
> + kfree(new_bw);
> + return -ENOMEM;
> + }
> +
> + /*
> + * Update bandwidth info, even in manual mode. That way, when switching
> + * to auto mode in the future, iw_table can be overwritten using
> + * accurate bw data.
> + */
> + mutex_lock(&iw_table_lock);
> +
> + old_bw = node_bw_table;
> + if (old_bw)
> + memcpy(new_bw, old_bw, nr_node_ids * sizeof(unsigned int));
> + new_bw[node] = bw_val;
> + node_bw_table = new_bw;
> +
> + /* wi_state not initialized yet; assume auto == true */
> + if (!rcu_access_pointer(wi_state))
> + goto reduce;
> +
> + old_wi_state = rcu_dereference_protected(wi_state,
> + lockdep_is_held(&iw_table_lock));
> + if (old_wi_state->mode_auto)
> + goto reduce;
> +
> + mutex_unlock(&iw_table_lock);
> + kfree(new_wi_state);
> + kfree(old_bw);
> + return 0;
> +
> +reduce:
> + new_wi_state->mode_auto = true;
> + reduce_interleave_weights(new_bw, new_wi_state->iw_table);
> +
> + rcu_assign_pointer(wi_state, new_wi_state);
> + mutex_unlock(&iw_table_lock);
> + if (old_wi_state) {
> + synchronize_rcu();
> + kfree(old_wi_state);
> + }
> + kfree(old_bw);
> +
> + return 0;
> +}
> +
> /**
> * numa_nearest_node - Find nearest node by state
> * @node: Node id to start the search
> @@ -1988,34 +2109,33 @@ static unsigned int weighted_interleave_nid(struct mempolicy *pol, pgoff_t ilx)
> u8 *table;
> unsigned int weight_total = 0;
> u8 weight;
> - int nid;
> + int nid = 0;
>
> nr_nodes = read_once_policy_nodemask(pol, &nodemask);
> if (!nr_nodes)
> return numa_node_id();
>
> rcu_read_lock();
> - table = rcu_dereference(iw_table);
> + if (!rcu_access_pointer(wi_state))
> + goto out;
> +
> + table = rcu_dereference(wi_state)->iw_table;
> /* calculate the total weight */
> - for_each_node_mask(nid, nodemask) {
> - /* detect system default usage */
> - weight = table ? table[nid] : 1;
> - weight = weight ? weight : 1;
> - weight_total += weight;
> - }
> + for_each_node_mask(nid, nodemask)
> + weight_total += table ? table[nid] : 1;
>
> /* Calculate the node offset based on totals */
> target = ilx % weight_total;
> nid = first_node(nodemask);
> while (target) {
> /* detect system default usage */
> - weight = table ? table[nid] : 1;
> - weight = weight ? weight : 1;
> + weight = table[nid];
> if (target < weight)
> break;
> target -= weight;
> nid = next_node_in(nid, nodemask);
> }
> +out:
> rcu_read_unlock();
> return nid;
> }
> @@ -2411,13 +2531,14 @@ static unsigned long alloc_pages_bulk_weighted_interleave(gfp_t gfp,
> struct mempolicy *pol, unsigned long nr_pages,
> struct page **page_array)
> {
> + struct weighted_interleave_state *state;
> struct task_struct *me = current;
> unsigned int cpuset_mems_cookie;
> unsigned long total_allocated = 0;
> unsigned long nr_allocated = 0;
> unsigned long rounds;
> unsigned long node_pages, delta;
> - u8 *table, *weights, weight;
> + u8 *weights, weight;
> unsigned int weight_total = 0;
> unsigned long rem_pages = nr_pages;
> nodemask_t nodes;
> @@ -2467,17 +2588,19 @@ static unsigned long alloc_pages_bulk_weighted_interleave(gfp_t gfp,
> return total_allocated;
>
> rcu_read_lock();
> - table = rcu_dereference(iw_table);
> - if (table)
> - memcpy(weights, table, nr_node_ids);
> - rcu_read_unlock();
> + if (rcu_access_pointer(wi_state)) {
> + state = rcu_dereference(wi_state);
> + memcpy(weights, state->iw_table, nr_node_ids * sizeof(u8));
> + rcu_read_unlock();
> + } else {
> + rcu_read_unlock();
> + for (i = 0; i < nr_node_ids; i++)
> + weights[i] = 1;
> + }
>
> /* calculate total, detect system default usage */
> - for_each_node_mask(node, nodes) {
> - if (!weights[node])
> - weights[node] = 1;
> + for_each_node_mask(node, nodes)
> weight_total += weights[node];
> - }
>
> /*
> * Calculate rounds/partial rounds to minimize __alloc_pages_bulk calls.
> @@ -3402,36 +3525,113 @@ static ssize_t node_show(struct kobject *kobj, struct kobj_attribute *attr,
> static ssize_t node_store(struct kobject *kobj, struct kobj_attribute *attr,
> const char *buf, size_t count)
> {
> + struct weighted_interleave_state *new_wi_state, *old_wi_state = NULL;
> struct iw_node_attr *node_attr;
> - u8 *new;
> - u8 *old;
> u8 weight = 0;
> + int i;
>
> node_attr = container_of(attr, struct iw_node_attr, kobj_attr);
> if (count == 0 || sysfs_streq(buf, ""))
> weight = 0;
> - else if (kstrtou8(buf, 0, &weight))
> + else if (kstrtou8(buf, 0, &weight) || weight == 0)
> return -EINVAL;
>
> - new = kzalloc(nr_node_ids, GFP_KERNEL);
> - if (!new)
> + new_wi_state = kzalloc(struct_size(new_wi_state, iw_table, nr_node_ids),
> + GFP_KERNEL);
> + if (!new_wi_state)
> return -ENOMEM;
>
> mutex_lock(&iw_table_lock);
> - old = rcu_dereference_protected(iw_table,
> + if (rcu_access_pointer(wi_state)) {
> + old_wi_state = rcu_dereference_protected(wi_state,
> lockdep_is_held(&iw_table_lock));
> - if (old)
> - memcpy(new, old, nr_node_ids);
> - new[node_attr->nid] = weight;
> - rcu_assign_pointer(iw_table, new);
> + memcpy(new_wi_state->iw_table, old_wi_state->iw_table,
> + nr_node_ids * sizeof(u8));
> + } else {
> + for (i = 0; i < nr_node_ids; i++)
> + new_wi_state->iw_table[i] = 1;
> + }
> + new_wi_state->iw_table[node_attr->nid] = weight;
> + new_wi_state->mode_auto = false;
> +
> + rcu_assign_pointer(wi_state, new_wi_state);
> mutex_unlock(&iw_table_lock);
> - synchronize_rcu();
> - kfree(old);
> + if (old_wi_state) {
> + synchronize_rcu();
> + kfree(old_wi_state);
> + }
> return count;
> }
>
> static struct iw_node_attr **node_attrs;
>
> +static ssize_t weighted_interleave_auto_show(struct kobject *kobj,
> + struct kobj_attribute *attr, char *buf)
> +{
> + bool wi_auto = true;
> +
> + rcu_read_lock();
> + if (rcu_access_pointer(wi_state))
> + wi_auto = rcu_dereference(wi_state)->mode_auto;
> + rcu_read_unlock();
> +
> + return sysfs_emit(buf, "%s\n", str_true_false(wi_auto));
> +}
> +
> +static ssize_t weighted_interleave_auto_store(struct kobject *kobj,
> + struct kobj_attribute *attr, const char *buf, size_t count)
> +{
> + struct weighted_interleave_state *new_wi_state, *old_wi_state = NULL;
> + unsigned int *bw;
> + bool input;
> + int i;
> +
> + if (kstrtobool(buf, &input))
> + return -EINVAL;
> +
> + new_wi_state = kzalloc(struct_size(new_wi_state, iw_table, nr_node_ids),
> + GFP_KERNEL);
> + if (!new_wi_state)
> + return -ENOMEM;
> + mutex_lock(&iw_table_lock);
> +
> + if (!input) {
> + if (rcu_access_pointer(wi_state)) {
> + old_wi_state = rcu_dereference_protected(wi_state,
> + lockdep_is_held(&iw_table_lock));
> + memcpy(new_wi_state->iw_table, old_wi_state->iw_table,
> + nr_node_ids * sizeof(u8));
> + } else {
> + for (i = 0; i < nr_node_ids; i++)
> + new_wi_state->iw_table[i] = 1;
> + }
> + goto update_wi_state;
> + }
> +
> + bw = node_bw_table;
> + if (!bw) {
> + mutex_unlock(&iw_table_lock);
> + kfree(new_wi_state);
> + return -ENODEV;
> + }
> +
> + new_wi_state->mode_auto = true;
> + reduce_interleave_weights(bw, new_wi_state->iw_table);
> +
> +update_wi_state:
> + rcu_assign_pointer(wi_state, new_wi_state);
> + mutex_unlock(&iw_table_lock);
> + if (old_wi_state) {
> + synchronize_rcu();
> + kfree(old_wi_state);
> + }
> + return count;
> +}
> +
> +static struct kobj_attribute wi_attr =
> + __ATTR(auto, 0664, weighted_interleave_auto_show,
> + weighted_interleave_auto_store);
> +
> static void sysfs_wi_node_release(struct iw_node_attr *node_attr,
> struct kobject *parent)
> {
> @@ -3489,6 +3689,15 @@ static int add_weight_node(int nid, struct kobject *wi_kobj)
> return 0;
> }
>
> +static struct attribute *wi_default_attrs[] = {
> + &wi_attr.attr,
> + NULL
> +};
> +
> +static const struct attribute_group wi_attr_group = {
> + .attrs = wi_default_attrs,
> +};
> +
> static int add_weighted_interleave_group(struct kobject *root_kobj)
> {
> struct kobject *wi_kobj;
> @@ -3505,6 +3714,13 @@ static int add_weighted_interleave_group(struct kobject *root_kobj)
> return err;
> }
>
> + err = sysfs_create_group(wi_kobj, &wi_attr_group);
> + if (err) {
> + pr_err("failed to add sysfs [auto]\n");
> + kobject_put(wi_kobj);
> + return err;
> + }
> +
> for_each_node_state(nid, N_POSSIBLE) {
> err = add_weight_node(nid, wi_kobj);
> if (err) {
> @@ -3519,15 +3735,22 @@ static int add_weighted_interleave_group(struct kobject *root_kobj)
>
> static void mempolicy_kobj_release(struct kobject *kobj)
> {
> - u8 *old;
> + struct weighted_interleave_state *old_wi_state;
>
> mutex_lock(&iw_table_lock);
> - old = rcu_dereference_protected(iw_table,
> - lockdep_is_held(&iw_table_lock));
> - rcu_assign_pointer(iw_table, NULL);
> + if (!rcu_access_pointer(wi_state)) {
> + mutex_unlock(&iw_table_lock);
> + goto out;
> + }
> +
> + old_wi_state = rcu_dereference_protected(wi_state,
> + lockdep_is_held(&iw_table_lock));
> +
> + rcu_assign_pointer(wi_state, NULL);
> mutex_unlock(&iw_table_lock);
> synchronize_rcu();
> - kfree(old);
> + kfree(old_wi_state);
> +out:
> kfree(node_attrs);
> kfree(kobj);
> }
> --
> 2.43.5
>