[Cluster-devel] [PATCH 15/29] gfs2: gfs2_glock_get: Wait on freeing glocks
Bob Peterson
rpeterso at redhat.com
Mon Sep 4 02:51:03 UTC 2017
From: Andreas Gruenbacher <agruenba at redhat.com>
Keep glocks in their hash table until they are freed instead of removing
them when their last reference is dropped. This allows to wait for any
previous instances of a glock to go away in gfs2_glock_get before
creating a new glocks.
Special thanks to Andy Price for finding and fixing a problem which also
required us to delete the rcu_read_unlock from the error case in function
gfs2_glock_get.
Signed-off-by: Andreas Gruenbacher <agruenba at redhat.com>
Signed-off-by: Bob Peterson <rpeterso at redhat.com>
---
fs/gfs2/glock.c | 126 ++++++++++++++++++++++++++++++++++++++++++++++----------
1 file changed, 104 insertions(+), 22 deletions(-)
diff --git a/fs/gfs2/glock.c b/fs/gfs2/glock.c
index 1029340fc8ba..11d48b964047 100644
--- a/fs/gfs2/glock.c
+++ b/fs/gfs2/glock.c
@@ -15,6 +15,7 @@
#include <linux/buffer_head.h>
#include <linux/delay.h>
#include <linux/sort.h>
+#include <linux/hash.h>
#include <linux/jhash.h>
#include <linux/kallsyms.h>
#include <linux/gfs2_ondisk.h>
@@ -80,6 +81,66 @@ static struct rhashtable_params ht_parms = {
static struct rhashtable gl_hash_table;
+#define GLOCK_WAIT_TABLE_BITS 12
+#define GLOCK_WAIT_TABLE_SIZE (1 << GLOCK_WAIT_TABLE_BITS)
+static wait_queue_head_t glock_wait_table[GLOCK_WAIT_TABLE_SIZE] __cacheline_aligned;
+
+struct wait_glock_queue {
+ struct lm_lockname *name;
+ wait_queue_entry_t wait;
+};
+
+static int glock_wake_function(wait_queue_entry_t *wait, unsigned int mode,
+ int sync, void *key)
+{
+ struct wait_glock_queue *wait_glock =
+ container_of(wait, struct wait_glock_queue, wait);
+ struct lm_lockname *wait_name = wait_glock->name;
+ struct lm_lockname *wake_name = key;
+
+ if (wake_name->ln_sbd != wait_name->ln_sbd ||
+ wake_name->ln_number != wait_name->ln_number ||
+ wake_name->ln_type != wait_name->ln_type)
+ return 0;
+ return autoremove_wake_function(wait, mode, sync, key);
+}
+
+static wait_queue_head_t *glock_waitqueue(struct lm_lockname *name)
+{
+ u32 hash = jhash2((u32 *)name, sizeof(*name) / 4, 0);
+
+ return glock_wait_table + hash_32(hash, GLOCK_WAIT_TABLE_BITS);
+}
+
+static void prepare_to_wait_on_glock(wait_queue_head_t **wq,
+ struct wait_glock_queue *wait,
+ struct lm_lockname *name)
+{
+ wait->name = name;
+ init_wait(&wait->wait);
+ wait->wait.func = glock_wake_function;
+ *wq = glock_waitqueue(name);
+ prepare_to_wait(*wq, &wait->wait, TASK_UNINTERRUPTIBLE);
+}
+
+static void finish_wait_on_glock(wait_queue_head_t *wq,
+ struct wait_glock_queue *wait)
+{
+ finish_wait(wq, &wait->wait);
+}
+
+/**
+ * wake_up_glock - Wake up waiters on a glock
+ * @gl: the glock
+ */
+static void wake_up_glock(struct gfs2_glock *gl)
+{
+ wait_queue_head_t *wq = glock_waitqueue(&gl->gl_name);
+
+ if (waitqueue_active(wq))
+ __wake_up(wq, TASK_NORMAL, 1, &gl->gl_name);
+}
+
static void gfs2_glock_dealloc(struct rcu_head *rcu)
{
struct gfs2_glock *gl = container_of(rcu, struct gfs2_glock, gl_rcu);
@@ -96,6 +157,9 @@ void gfs2_glock_free(struct gfs2_glock *gl)
{
struct gfs2_sbd *sdp = gl->gl_name.ln_sbd;
+ rhashtable_remove_fast(&gl_hash_table, &gl->gl_node, ht_parms);
+ smp_mb();
+ wake_up_glock(gl);
call_rcu(&gl->gl_rcu, gfs2_glock_dealloc);
if (atomic_dec_and_test(&sdp->sd_glock_disposal))
wake_up(&sdp->sd_glock_wait);
@@ -194,7 +258,6 @@ static void __gfs2_glock_put(struct gfs2_glock *gl)
gfs2_glock_remove_from_lru(gl);
spin_unlock(&gl->gl_lockref.lock);
- rhashtable_remove_fast(&gl_hash_table, &gl->gl_node, ht_parms);
GLOCK_BUG_ON(gl, !list_empty(&gl->gl_holders));
GLOCK_BUG_ON(gl, mapping && mapping->nrpages);
trace_gfs2_glock_put(gl);
@@ -679,6 +742,36 @@ static void glock_work_func(struct work_struct *work)
spin_unlock(&gl->gl_lockref.lock);
}
+static struct gfs2_glock *find_insert_glock(struct lm_lockname *name,
+ struct gfs2_glock *new)
+{
+ struct wait_glock_queue wait;
+ wait_queue_head_t *wq;
+ struct gfs2_glock *gl;
+
+again:
+ prepare_to_wait_on_glock(&wq, &wait, name);
+ rcu_read_lock();
+ if (new) {
+ gl = rhashtable_lookup_get_insert_fast(&gl_hash_table,
+ &new->gl_node, ht_parms);
+ if (IS_ERR(gl))
+ goto out;
+ } else {
+ gl = rhashtable_lookup_fast(&gl_hash_table,
+ name, ht_parms);
+ }
+ if (gl && !lockref_get_not_dead(&gl->gl_lockref)) {
+ rcu_read_unlock();
+ schedule();
+ goto again;
+ }
+out:
+ rcu_read_unlock();
+ finish_wait_on_glock(wq, &wait);
+ return gl;
+}
+
/**
* gfs2_glock_get() - Get a glock, or create one if one doesn't exist
* @sdp: The GFS2 superblock
@@ -705,15 +798,11 @@ int gfs2_glock_get(struct gfs2_sbd *sdp, u64 number,
struct kmem_cache *cachep;
int ret = 0;
- rcu_read_lock();
- gl = rhashtable_lookup_fast(&gl_hash_table, &name, ht_parms);
- if (gl && !lockref_get_not_dead(&gl->gl_lockref))
- gl = NULL;
- rcu_read_unlock();
-
- *glp = gl;
- if (gl)
+ gl = find_insert_glock(&name, NULL);
+ if (gl) {
+ *glp = gl;
return 0;
+ }
if (!create)
return -ENOENT;
@@ -767,10 +856,7 @@ int gfs2_glock_get(struct gfs2_sbd *sdp, u64 number,
mapping->writeback_index = 0;
}
-again:
- rcu_read_lock();
- tmp = rhashtable_lookup_get_insert_fast(&gl_hash_table, &gl->gl_node,
- ht_parms);
+ tmp = find_insert_glock(&name, gl);
if (!tmp) {
*glp = gl;
goto out;
@@ -779,13 +865,7 @@ int gfs2_glock_get(struct gfs2_sbd *sdp, u64 number,
ret = PTR_ERR(tmp);
goto out_free;
}
- if (lockref_get_not_dead(&tmp->gl_lockref)) {
- *glp = tmp;
- goto out_free;
- }
- rcu_read_unlock();
- cond_resched();
- goto again;
+ *glp = tmp;
out_free:
kfree(gl->gl_lksb.sb_lvbptr);
@@ -793,7 +873,6 @@ int gfs2_glock_get(struct gfs2_sbd *sdp, u64 number,
atomic_dec(&sdp->sd_glock_disposal);
out:
- rcu_read_unlock();
return ret;
}
@@ -1806,7 +1885,7 @@ static int gfs2_sbstats_seq_show(struct seq_file *seq, void *iter_ptr)
int __init gfs2_glock_init(void)
{
- int ret;
+ int i, ret;
ret = rhashtable_init(&gl_hash_table, &ht_parms);
if (ret < 0)
@@ -1835,6 +1914,9 @@ int __init gfs2_glock_init(void)
return ret;
}
+ for (i = 0; i < GLOCK_WAIT_TABLE_SIZE; i++)
+ init_waitqueue_head(glock_wait_table + i);
+
return 0;
}
--
2.13.5
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