[RFC v1 09/11] vfs: fork one private kthread to update temperature info

zwu.kernel
2012-09-17T07:19:53Z

Fork and run one kernel kthread to calculate
that temperature based on some metrics kept
in custom frequency data structs, and store
the info in the hash table.

Signed-off-by: Zhi Yong Wu <wuzhy@linux.vnet.ibm.com>
---
fs/hot_hash.c | 302 +++++++++++++++++++++++++++++++++++++++++++++
fs/hot_hash.h | 82 ++++++++++++
fs/hot_rb.c | 132 +++++++++++++++++++-
fs/hot_rb.h | 15 +++
fs/hot_track.c | 31 +++++
include/linux/hot_track.h | 5 +
6 files changed, 561 insertions(+), 6 deletions(-)

diff --git a/fs/hot_hash.c b/fs/hot_hash.c
index e415784..c13ffb1 100644
--- a/fs/hot_hash.c
+++ b/fs/hot_hash.c
@@ -18,6 +18,7 @@
#include <linux/hardirq.h>
#include <linux/hash.h>
#include <linux/types.h>
+#include <linux/kthread.h>
#include <linux/freezer.h>
#include <linux/fs.h>
#include "hot_rb.h"
@@ -65,3 +66,304 @@ void hot_hash_table_init(struct hot_info *root)
}
}

+static void hot_hash_node_free(struct hlist_head *head)
+{
+ struct hlist_node *pos = NULL, *pos2 = NULL;
+ struct hot_hash_node *heatnode = NULL;
+
+ hlist_for_each_safe(pos, pos2, head) {
+ heatnode = hlist_entry(pos,
+ struct hot_hash_node,
+ hashnode);
+ hlist_del(pos);
+ kfree(heatnode);
+ }
+
+}
+
+void hot_hash_table_free(struct hot_info *root)
+{
+ int i;
+
+ /* Free node/range heat hash lists */
+ for (i = 0; i < HEAT_HASH_SIZE; i++) {
+ hot_hash_node_free(&root->heat_inode_hl[i].hashhead);
+ hot_hash_node_free(&root->heat_range_hl[i].hashhead);
+ }
+}
+
+static u64 hot_hash_shift(u64 counter, u32 bits, bool shift_dir)
+{
+ if (shift_dir)
+ return counter << bits;
+ else
+ return counter >> bits;
+}
+
+/*
+ * hot_hash_calc_temperature() is responsible for distilling the six heat
+ * criteria, which are described in detail in hot_hash.h) down into a single
+ * temperature value for the data, which is an integer between 0
+ * and HEAT_MAX_VALUE.
+ *
+ * To accomplish this, the raw values from the hot_freq_data structure
+ * are shifted various ways in order to make the temperature calculation more
+ * or less sensitive to each value.
+ *
+ * Once this calibration has happened, we do some additional normalization and
+ * make sure that everything fits nicely in a u32. From there, we take a very
+ * rudimentary kind of "average" of each of the values, where the *_COEFF_POWER
+ * values act as weights for the average.
+ *
+ * Finally, we use the HEAT_HASH_BITS value, which determines the size of the
+ * heat hash list, to normalize the temperature to the proper granularity.
+ */
+int hot_hash_calc_temperature(struct hot_freq_data *freq_data)
+{
+ u64 result = 0;
+
+ struct timespec ckt = current_kernel_time();
+ u64 cur_time = timespec_to_ns(&ckt);
+
+ u32 nrr_heat = (u32)hot_hash_shift((u64)freq_data->nr_reads,
+ NRR_MULTIPLIER_POWER, true);
+ u32 nrw_heat = (u32)hot_hash_shift((u64)freq_data->nr_writes,
+ NRW_MULTIPLIER_POWER, true);
+
+ u64 ltr_heat =
+ hot_hash_shift((cur_time - timespec_to_ns(&freq_data->last_read_time)),
+ LTR_DIVIDER_POWER, false);
+ u64 ltw_heat =
+ hot_hash_shift((cur_time - timespec_to_ns(&freq_data->last_write_time)),
+ LTW_DIVIDER_POWER, false);
+
+ u64 avr_heat =
+ hot_hash_shift((((u64) -1) - freq_data->avg_delta_reads),
+ AVR_DIVIDER_POWER, false);
+ u64 avw_heat =
+ hot_hash_shift((((u64) -1) - freq_data->avg_delta_writes),
+ AVW_DIVIDER_POWER, false);
+
+ /* ltr_heat is now guaranteed to be u32 safe */
+ if (ltr_heat >= hot_hash_shift((u64) 1, 32, true))
+ ltr_heat = 0;
+ else
+ ltr_heat = hot_hash_shift((u64) 1, 32, true) - ltr_heat;
+
+ /* ltw_heat is now guaranteed to be u32 safe */
+ if (ltw_heat >= hot_hash_shift((u64) 1, 32, true))
+ ltw_heat = 0;
+ else
+ ltw_heat = hot_hash_shift((u64) 1, 32, true) - ltw_heat;
+
+ /* avr_heat is now guaranteed to be u32 safe */
+ if (avr_heat >= hot_hash_shift((u64) 1, 32, true))
+ avr_heat = (u32) -1;
+
+ /* avw_heat is now guaranteed to be u32 safe */
+ if (avw_heat >= hot_hash_shift((u64) 1, 32, true))
+ avw_heat = (u32) -1;
+
+ nrr_heat = (u32)hot_hash_shift((u64)nrr_heat,
+ (3 - NRR_COEFF_POWER), false);
+ nrw_heat = (u32)hot_hash_shift((u64)nrw_heat,
+ (3 - NRW_COEFF_POWER), false);
+ ltr_heat = hot_hash_shift(ltr_heat, (3 - LTR_COEFF_POWER), false);
+ ltw_heat = hot_hash_shift(ltw_heat, (3 - LTW_COEFF_POWER), false);
+ avr_heat = hot_hash_shift(avr_heat, (3 - AVR_COEFF_POWER), false);
+ avw_heat = hot_hash_shift(avw_heat, (3 - AVW_COEFF_POWER), false);
+
+ result = nrr_heat + nrw_heat + (u32) ltr_heat +
+ (u32) ltw_heat + (u32) avr_heat + (u32) avw_heat;
+
+ return result >> (32 - HEAT_HASH_BITS);
+}
+
+int hot_hash_is_aging(struct hot_freq_data *freq_data)
+{
+ int ret = 0;
+ struct timespec ckt = current_kernel_time();
+
+ u64 cur_time = timespec_to_ns(&ckt);
+ u64 last_read_ns =
+ (cur_time - timespec_to_ns(&freq_data->last_read_time));
+ u64 last_write_ns =
+ (cur_time - timespec_to_ns(&freq_data->last_write_time));
+ u64 kick_ns = TIME_TO_KICK * (u64)1000000000;
+
+ if ((last_read_ns > kick_ns) && (last_write_ns > kick_ns))
+ ret = 1;
+
+ return ret;
+}
+
+/*
+ * Calc a new temperature and, if necessary, move the heat_node corresponding
+ * to this inode or range to the proper hashlist with the new temperature
+ */
+void hot_hash_update_hash_table(struct hot_freq_data *freq_data,
+ struct hot_info *root)
+{
+ int temperature = 0;
+ int moved = 0;
+ struct hot_hash_head *buckets, *current_bucket = NULL;
+ struct hot_inode_item *he;
+ struct hot_range_item *hr;
+
+ if (freq_data->flags & FREQ_DATA_TYPE_INODE) {
+ he = hot_freq_data_get_he(freq_data);
+ buckets = root->heat_inode_hl;
+
+ spin_lock(&he->lock);
+ temperature = hot_hash_calc_temperature(freq_data);
+ freq_data->last_temperature = temperature;
+ spin_unlock(&he->lock);
+
+ if (he == NULL)
+ return;
+
+ spin_lock(&he->heat_node->lock);
+ if (he->heat_node->hlist == NULL) {
+ current_bucket = buckets + temperature;
+ moved = 1;
+ } else {
+ write_lock(&he->heat_node->hlist->rwlock);
+ current_bucket = he->heat_node->hlist;
+ if (current_bucket->temperature != temperature) {
+ hlist_del(&he->heat_node->hashnode);
+ current_bucket = buckets + temperature;
+ moved = 1;
+ }
+ write_unlock(&he->heat_node->hlist->rwlock);
+ }
+
+ if (moved) {
+ write_lock(&current_bucket->rwlock);
+ hlist_add_head(&he->heat_node->hashnode,
+ &current_bucket->hashhead);
+ he->heat_node->hlist = current_bucket;
+ write_unlock(&current_bucket->rwlock);
+ }
+ spin_unlock(&he->heat_node->lock);
+ } else if (freq_data->flags & FREQ_DATA_TYPE_RANGE) {
+ hr = hot_freq_data_get_hr(freq_data);
+ buckets = root->heat_range_hl;
+
+ spin_lock(&hr->lock);
+ temperature = hot_hash_calc_temperature(freq_data);
+ freq_data->last_temperature = temperature;
+ spin_unlock(&hr->lock);
+
+ if (hr == NULL)
+ return;
+
+ spin_lock(&hr->heat_node->lock);
+ if (hr->heat_node->hlist == NULL) {
+ current_bucket = buckets + temperature;
+ moved = 1;
+ } else {
+ write_lock(&hr->heat_node->hlist->rwlock);
+ current_bucket = hr->heat_node->hlist;
+ if (current_bucket->temperature != temperature) {
+ hlist_del(&hr->heat_node->hashnode);
+ current_bucket = buckets + temperature;
+ moved = 1;
+ }
+ write_unlock(&hr->heat_node->hlist->rwlock);
+ }
+
+ if (moved) {
+ write_lock(&current_bucket->rwlock);
+ hlist_add_head(&hr->heat_node->hashnode,
+ &current_bucket->hashhead);
+ hr->heat_node->hlist = current_bucket;
+ write_unlock(&current_bucket->rwlock);
+ }
+ spin_unlock(&hr->heat_node->lock);
+ }
+}
+
+/*
+ * Update temperatures for each hot inode item and
+ * hot range item for aging purposes
+ */
+static void hot_hash_temperature_update_iterator(struct hot_info *root)
+{
+ struct hot_inode_item *current_hot_inode;
+ struct hot_inode_tree *hot_inode_tree;
+ unsigned long inode_num;
+
+ hot_inode_tree = &root->hot_inode_tree;
+
+ /* walk the inode tree */
+ current_hot_inode = hot_rb_find_next_hot_inode(root, 0);
+ while (current_hot_inode) {
+ hot_hash_update_hash_table(
+ &current_hot_inode->hot_freq_data, root);
+ hot_rb_update_range_data(current_hot_inode, root);
+ inode_num = current_hot_inode->i_ino;
+ hot_rb_free_hot_inode_item(current_hot_inode);
+ current_hot_inode = hot_rb_find_next_hot_inode(root,
+ inode_num + 1);
+ }
+}
+
+/* Determine if there is hot data tracking to be enabled */
+static bool hot_hash_global_hot_track(void)
+{
+ struct super_block *sb;
+ bool ret = false;
+
+ spin_lock(&sb_lock);
+ list_for_each_entry(sb, &super_blocks, s_list) {
+ if (hlist_unhashed(&sb->s_instances))
+ continue;
+ if (sb->s_hotinfo.mount_opt & HOT_MOUNT_HOT_TRACK)
+ ret = true;
+ }
+ spin_unlock(&sb_lock);
+
+ return ret;
+}
+
+/*
+ * kthread iterates each hot_inode_item and hot_range_item
+ * and update temperatures to be shifted in heat hash table
+ * for purposes of relocation and such hot file detection
+ */
+int hot_hash_temperature_update_kthread(void *arg)
+{
+ struct super_block *sb;
+ struct hot_info *root;
+ unsigned long delay;
+
+ do {
+ spin_lock(&sb_lock);
+ list_for_each_entry(sb, &super_blocks, s_list) {
+ if (hlist_unhashed(&sb->s_instances))
+ continue;
+ delay = HZ * HEAT_UPDATE_DELAY;
+ root = &sb->s_hotinfo;
+ if (mutex_trylock(
+ &root->hot_data_update_kthread_mutex)) {
+ hot_hash_temperature_update_iterator(root);
+ mutex_unlock(
+ &root->hot_data_update_kthread_mutex);
+ }
+ if (unlikely(freezing(current))) {
+ __refrigerator(true);
+ } else {
+ set_current_state(TASK_INTERRUPTIBLE);
+ if (!kthread_should_stop()) {
+ spin_unlock(&sb_lock);
+ schedule_timeout(delay);
+ spin_lock(&sb_lock);
+ }
+ __set_current_state(TASK_RUNNING);
+ }
+ }
+ spin_unlock(&sb_lock);
+ } while (!kthread_should_stop() || !hot_hash_global_hot_track());
+
+ return 0;
+}
diff --git a/fs/hot_hash.h b/fs/hot_hash.h
index 29476f5..6d55f42 100644
--- a/fs/hot_hash.h
+++ b/fs/hot_hash.h
@@ -17,10 +17,92 @@
#include <linux/hash.h>
#include <linux/hot_track.h>

+/* time to quit keeping track of tracking data (seconds)*/
+#define TIME_TO_KICK 400
+
+/* set how often to update temperatures (seconds) */
+#define HEAT_UPDATE_DELAY 400
+
+/*
+ * The following comments explain what exactly comprises a unit of heat.
+ *
+ * Each of six values of heat are calculated and combined in order to form an
+ * overall temperature for the data:
+ *
+ * NRR - number of reads since mount
+ * NRW - number of writes since mount
+ * LTR - time elapsed since last read (ns)
+ * LTW - time elapsed since last write (ns)
+ * AVR - average delta between recent reads (ns)
+ * AVW - average delta between recent writes (ns)
+ *
+ * These values are divided (right-shifted) according to the *_DIVIDER_POWER
+ * values defined below to bring the numbers into a reasonable range. You can
+ * modify these values to fit your needs. However, each heat unit is a u32 and
+ * thus maxes out at 2^32 - 1. Therefore, you must choose your dividers quite
+ * carefully or else they could max out or be stuck at zero quite easily.
+ *
+ * (E.g., if you chose AVR_DIVIDER_POWER = 0, nothing less than 4s of atime
+ * delta would bring the temperature above zero, ever.)
+ *
+ * Finally, each value is added to the overall temperature between 0 and 8
+ * times, depending on its *_COEFF_POWER value. Note that the coefficients are
+ * also actually implemented with shifts, so take care to treat these values
+ * as powers of 2. (I.e., 0 means we'll add it to the temp once; 1 = 2x, etc.)
+ */
+
+/* NRR/NRW heat unit = 2^X accesses */
+#define NRR_MULTIPLIER_POWER 20
+#define NRR_COEFF_POWER 0
+#define NRW_MULTIPLIER_POWER 20
+#define NRW_COEFF_POWER 0
+
+/* LTR/LTW heat unit = 2^X ns of age */
+#define LTR_DIVIDER_POWER 30
+#define LTR_COEFF_POWER 1
+#define LTW_DIVIDER_POWER 30
+#define LTW_COEFF_POWER 1
+
+/*
+ * AVR/AVW cold unit = 2^X ns of average delta
+ * AVR/AVW heat unit = HEAT_MAX_VALUE - cold unit
+ *
+ * E.g., data with an average delta between 0 and 2^X ns will have a cold value
+ * of 0, which means a heat value equal to HEAT_MAX_VALUE.
+ */
+#define AVR_DIVIDER_POWER 40
+#define AVR_COEFF_POWER 0
+#define AVW_DIVIDER_POWER 40
+#define AVW_COEFF_POWER 0
+
+/* macros to wrap container_of()'s for hot data structs */
+#define hot_freq_data_get_he(x) \
+ ((struct hot_inode_item *) container_of(x, \
+ struct hot_inode_item, hot_freq_data))
+#define hot_freq_data_get_hr(x) \
+ ((struct hot_range_item *) container_of(x, \
+ struct hot_range_item, hot_freq_data))
+
+struct hot_info;
+
void hot_hash_node_init(void *_node);

int __init hot_hash_node_cache_init(void);

void hot_hash_table_init(struct hot_info *root);
+void hot_hash_table_free(struct hot_info *root);
+
+/*
+ * Returns a value from 0 to HEAT_MAX_VALUE indicating the temperature of the
+ * file (and consequently its bucket number in hash list) (see hot_hash.c)
+ */
+int hot_hash_calc_temperature(struct hot_freq_data *freq_data);
+
+int hot_hash_is_aging(struct hot_freq_data *freq_data);
+
+void hot_hash_update_hash_table(struct hot_freq_data *freq_data,
+ struct hot_info *root);
+
+int hot_hash_temperature_update_kthread(void *arg);

#endif /* __HOT_HASH__ */
diff --git a/fs/hot_rb.c b/fs/hot_rb.c
index 196f4ed..f48634f 100644
--- a/fs/hot_rb.c
+++ b/fs/hot_rb.c
@@ -399,9 +399,13 @@ static struct hot_inode_item *hot_rb_update_inode_freq(struct inode *inode,
write_unlock(&hitree->lock);
}

- spin_lock(&he->lock);
- hot_rb_update_freq(&he->hot_freq_data, rw);
- spin_unlock(&he->lock);
+ if (!hot_track_temperature_update_kthread
+ || hot_track_temperature_update_kthread->pid != current->pid) {
+ spin_lock(&he->lock);
+ hot_rb_update_freq(&he->hot_freq_data, rw);
+ spin_unlock(&he->lock);
+ hot_hash_update_hash_table(&he->hot_freq_data, root);
+ }

out:
return he;
@@ -448,9 +452,14 @@ static bool hot_rb_update_range_freq(struct hot_inode_item *he,
write_unlock(&hrtree->lock);
}

- spin_lock(&hr->lock);
- hot_rb_update_freq(&hr->hot_freq_data, rw);
- spin_unlock(&hr->lock);
+ if (!hot_track_temperature_update_kthread
+ || hot_track_temperature_update_kthread->pid != current->pid) {
+ spin_lock(&hr->lock);
+ hot_rb_update_freq(&hr->hot_freq_data, rw);
+ spin_unlock(&hr->lock);
+ hot_hash_update_hash_table(&hr->hot_freq_data, root);
+ }
+
hot_rb_free_hot_range_item(hr);
}

@@ -509,6 +518,57 @@ void hot_rb_update_freq(struct hot_freq_data *freq_data, int rw)
}
}

+/* Walk the hot_inode_tree, locking as necessary */
+struct hot_inode_item *hot_rb_find_next_hot_inode(struct hot_info *root,
+ u64 objectid)
+{
+ struct rb_node *node;
+ struct rb_node *prev;
+ struct hot_inode_item *entry;
+
+ read_lock(&root->hot_inode_tree.lock);
+
+ node = root->hot_inode_tree.map.rb_node;
+ prev = NULL;
+ while (node) {
+ prev = node;
+ entry = rb_entry(node, struct hot_inode_item, rb_node);
+
+ if (objectid < entry->i_ino)
+ node = node->rb_left;
+ else if (objectid > entry->i_ino)
+ node = node->rb_right;
+ else
+ break;
+ }
+
+ if (!node) {
+ while (prev) {
+ entry = rb_entry(prev, struct hot_inode_item, rb_node);
+ if (objectid <= entry->i_ino) {
+ node = prev;
+ break;
+ }
+ prev = rb_next(prev);
+ }
+ }
+
+ if (node) {
+ entry = rb_entry(node, struct hot_inode_item, rb_node);
+ /*
+ * increase reference count to prevent pruning while
+ * caller is using the hot_inode_item
+ */
+ kref_get(&entry->refs);
+
+ read_unlock(&root->hot_inode_tree.lock);
+ return entry;
+ }
+
+ read_unlock(&root->hot_inode_tree.lock);
+ return NULL;
+}
+
/* main function to update access frequency from read/writepage(s) hooks */
void hot_rb_update_freqs(struct inode *inode, u64 start,
u64 len, int rw)
@@ -526,3 +586,63 @@ void hot_rb_update_freqs(struct inode *inode, u64 start,
hot_rb_free_hot_inode_item(he);
}
}
+
+/*
+ * take hot range that is now cold and remove from indexes and clean up
+ * any memory associted, involves removing hot range from rb tree, and
+ * heat hash lists, and freeing up all memory.
+ */
+static void hot_rb_remove_range_data(struct hot_inode_item *hot_inode,
+ struct hot_range_item *hr,
+ struct hot_info *root)
+{
+ /* remove range from rb tree */
+ hot_rb_remove_hot_range_item(&hot_inode->hot_range_tree, hr);
+
+ /* remove range from hash list */
+ spin_lock(&hr->heat_node->lock);
+ write_lock(&hr->heat_node->hlist->rwlock);
+ hlist_del(&hr->heat_node->hashnode);
+ write_unlock(&hr->heat_node->hlist->rwlock);
+ spin_unlock(&hr->heat_node->lock);
+
+ /*free up memory */
+ kfree(hr->heat_node);
+ hot_rb_free_hot_range_item(hr);
+}
+
+/* Update temperatures for each range item for aging purposes */
+void hot_rb_update_range_data(struct hot_inode_item *hot_inode,
+ struct hot_info *root)
+{
+ struct hot_range_tree *inode_range_tree;
+ struct rb_node *node;
+ struct rb_node *old_node;
+ struct hot_range_item *current_range;
+ int range_is_aging;
+
+ inode_range_tree = &hot_inode->hot_range_tree;
+ write_lock(&inode_range_tree->lock);
+ node = rb_first(&inode_range_tree->map);
+ /* Walk the hot_range_tree for inode */
+ while (node) {
+ current_range = rb_entry(node, struct hot_range_item, rb_node);
+ hot_hash_update_hash_table(&current_range->hot_freq_data, root);
+ old_node = node;
+ node = rb_next(node);
+
+ spin_lock(&current_range->lock);
+ range_is_aging = hot_hash_is_aging(&current_range->hot_freq_data);
+ spin_unlock(&current_range->lock);
+
+ if (range_is_aging) {
+ if (atomic_read(
+ &current_range->heat_node->refs.refcount) <= 1)
+ hot_rb_remove_range_data(hot_inode,
+ current_range, root);
+ }
+ }
+
+ write_unlock(&inode_range_tree->lock);
+}
+
diff --git a/fs/hot_rb.h b/fs/hot_rb.h
index f23c66f..14e7f43 100644
--- a/fs/hot_rb.h
+++ b/fs/hot_rb.h
@@ -48,8 +48,23 @@ int __init hot_rb_item_cache_init(void);

void hot_rb_inode_item_exit(void);
void hot_rb_range_item_exit(void);
+
+/*
+ * recalculates temperatures for inode or range
+ * and moves around in heat hash table based on temp
+ */
+void hot_rb_update_heat_hash_list(struct hot_freq_data *freq_data,
+ struct hot_info *root);
+
+struct hot_inode_item
+*hot_rb_find_next_hot_inode(struct hot_info *root,
+ u64 objectid);
void hot_rb_update_freq(struct hot_freq_data *freq_data, int rw);
void hot_rb_update_freqs(struct inode *inode, u64 start, u64 len,
int rw);

+/* Update temperatures for each range item for aging purposes */
+void hot_rb_update_range_data(struct hot_inode_item *hot_inode,
+ struct hot_info *root);
+
#endif /* __HOT_MAP__ */
diff --git a/fs/hot_track.c b/fs/hot_track.c
index 1aacff8..37bc28a 100644
--- a/fs/hot_track.c
+++ b/fs/hot_track.c
@@ -13,8 +13,11 @@
#include <linux/slab.h>
#include <linux/gfp.h>
#include <linux/parser.h>
+#include <linux/kthread.h>
#include "hot_track.h"

+struct task_struct *hot_track_temperature_update_kthread;
+
/*
* Regular mount options parser for -hottrack option.
* return false if no -hottrack is specified;
@@ -65,6 +68,30 @@ void __init hot_track_kmem_cache_init(void)
}

/*
+ * Fork and initialize kthread for each new mount point that
+ * periodically goes through hot inodes and hot ranges and ages them
+ * based on frequency of access
+ */
+static void hot_track_fork_temperature_update_kthread(void)
+{
+ if (hot_track_temperature_update_kthread)
+ return;
+
+ hot_track_temperature_update_kthread =
+ kthread_run(hot_hash_temperature_update_kthread, NULL,
+ "hot_temperature_update_kthread");
+ if (IS_ERR(hot_track_temperature_update_kthread))
+ kthread_stop(hot_track_temperature_update_kthread);
+}
+
+/* Stop the kthread to do temperature updates for all filesystems */
+static void hot_track_stop_temperature_update_kthread(void)
+{
+ if (hot_track_temperature_update_kthread)
+ kthread_stop(hot_track_temperature_update_kthread);
+}
+
+/*
* Initialize the data structures for hot data tracking.
*/
void hot_track_init(struct super_block *sb, const char *name)
@@ -72,10 +99,14 @@ void hot_track_init(struct super_block *sb, const char *name)
sb->s_hotinfo.mount_opt |= HOT_MOUNT_HOT_TRACK;
hot_rb_inode_tree_init(&sb->s_hotinfo.hot_inode_tree);
hot_hash_table_init(&sb->s_hotinfo);
+ hot_track_fork_temperature_update_kthread();
+ hot_debugfs_volume_init(name, sb);
}

void hot_track_exit(struct super_block *sb)
{
sb->s_hotinfo.mount_opt &= ~HOT_MOUNT_HOT_TRACK;
+ hot_track_stop_temperature_update_kthread();
+ hot_hash_table_free(&sb->s_hotinfo);
hot_rb_inode_tree_free(&sb->s_hotinfo);
}
diff --git a/include/linux/hot_track.h b/include/linux/hot_track.h
index 8bb9028..0f4c3b3 100644
--- a/include/linux/hot_track.h
+++ b/include/linux/hot_track.h
@@ -36,6 +36,8 @@
((TRACKING_HOT_TRACK(inode->i_sb)) && \
!(inode->i_flags & S_NOHOTDATATRACK))

+extern struct task_struct *hot_track_temperature_update_kthread;
+
/* kmem_cache pointers for slab caches */
extern struct kmem_cache *hot_hash_node_cache;

@@ -144,6 +146,9 @@ struct hot_info {

/* hash map of range temperature */
struct hot_hash_head heat_range_hl[HEAT_HASH_SIZE];
+
+ /* protects hot data items while being iterated and updated */
+ struct mutex hot_data_update_kthread_mutex;
};

extern void hot_rb_update_freqs(struct inode *inode,
--
1.7.6.5