Hi,
This patch introduces a new glock workqueue, gfs2_glock_final. The
workqueue merely does work to call dlm's unlock.
This prevents gfs2_evict_inode from calling dlm directly which
might block, waiting for DLM to unlock, which may be waiting for
something like a fence operation. By moving it to its own work queue,
the final put happens later, which allows the shrinker to continue,
and free memory, avoiding a livelock.
Signed-off-by: Bob Peterson <rpete...@redhat.com>
---
diff --git a/fs/gfs2/glock.c b/fs/gfs2/glock.c
index 795c2f3..9d0f3d5 100644
--- a/fs/gfs2/glock.c
+++ b/fs/gfs2/glock.c
@@ -63,6 +63,7 @@ static void do_xmote(struct gfs2_glock *gl, struct
gfs2_holder *gh, unsigned int
static struct dentry *gfs2_root;
static struct workqueue_struct *glock_workqueue;
+static struct workqueue_struct *gfs2_final_workqueue;
struct workqueue_struct *gfs2_delete_workqueue;
static LIST_HEAD(lru_list);
static atomic_t lru_count = ATOMIC_INIT(0);
@@ -152,6 +153,20 @@ static void gfs2_glock_remove_from_lru(struct gfs2_glock
*gl)
spin_unlock(&lru_lock);
}
+/* The purpose of this function is to tell dlm when a glock is not needed
+ * We can't do this directly from gfs2_glock_put because dlm may block while
+ * waiting for a fence operation to complete. But the fence may block on
+ * memory allocation, which may block on the shrinker, which may block on
+ * the evict code. So the buck stops here.
+ */
+static void final_work_func(struct work_struct *work)
+{
+ struct gfs2_glock *gl = container_of(work, struct gfs2_glock, gl_final);
+ struct gfs2_sbd *sdp = gl->gl_name.ln_sbd;
+
+ sdp->sd_lockstruct.ls_ops->lm_put_lock(gl);
+}
+
/**
* gfs2_glock_put() - Decrement reference count on glock
* @gl: The glock to put
@@ -160,7 +175,6 @@ static void gfs2_glock_remove_from_lru(struct gfs2_glock
*gl)
void gfs2_glock_put(struct gfs2_glock *gl)
{
- struct gfs2_sbd *sdp = gl->gl_name.ln_sbd;
struct address_space *mapping = gfs2_glock2aspace(gl);
if (lockref_put_or_lock(&gl->gl_lockref))
@@ -174,7 +188,7 @@ void gfs2_glock_put(struct gfs2_glock *gl)
GLOCK_BUG_ON(gl, !list_empty(&gl->gl_holders));
GLOCK_BUG_ON(gl, mapping && mapping->nrpages);
trace_gfs2_glock_put(gl);
- sdp->sd_lockstruct.ls_ops->lm_put_lock(gl);
+ BUG_ON(queue_work(gfs2_final_workqueue, &gl->gl_final) == 0);
}
/**
@@ -700,6 +714,7 @@ int gfs2_glock_get(struct gfs2_sbd *sdp, u64 number,
gl->gl_hold_time = GL_GLOCK_DFT_HOLD;
INIT_DELAYED_WORK(&gl->gl_work, glock_work_func);
INIT_WORK(&gl->gl_delete, delete_work_func);
+ INIT_WORK(&gl->gl_final, final_work_func);
mapping = gfs2_glock2aspace(gl);
if (mapping) {
@@ -1772,6 +1787,14 @@ int __init gfs2_glock_init(void)
rhashtable_destroy(&gl_hash_table);
return -ENOMEM;
}
+ gfs2_final_workqueue = alloc_workqueue("final_workqueue",
+ WQ_MEM_RECLAIM | WQ_HIGHPRI |
+ WQ_FREEZABLE, 0);
+ if (IS_ERR(gfs2_final_workqueue)) {
+ destroy_workqueue(glock_workqueue);
+ destroy_workqueue(gfs2_delete_workqueue);
+ return PTR_ERR(gfs2_final_workqueue);
+ }
register_shrinker(&glock_shrinker);
@@ -1784,6 +1807,7 @@ void gfs2_glock_exit(void)
rhashtable_destroy(&gl_hash_table);
destroy_workqueue(glock_workqueue);
destroy_workqueue(gfs2_delete_workqueue);
+ destroy_workqueue(gfs2_final_workqueue);
}
static void gfs2_glock_iter_next(struct gfs2_glock_iter *gi)
diff --git a/fs/gfs2/incore.h b/fs/gfs2/incore.h
index a6a3389..1b63fbc 100644
--- a/fs/gfs2/incore.h
+++ b/fs/gfs2/incore.h
@@ -361,6 +361,7 @@ struct gfs2_glock {
atomic_t gl_ail_count;
atomic_t gl_revokes;
struct delayed_work gl_work;
+ struct work_struct gl_final;
union {
/* For inode and iopen glocks only */
struct work_struct gl_delete;
diff --git a/fs/gfs2/inode.c b/fs/gfs2/inode.c
index 0357862..4232368 100644
--- a/fs/gfs2/inode.c
+++ b/fs/gfs2/inode.c
@@ -126,6 +126,8 @@ struct inode *gfs2_inode_lookup(struct super_block *sb,
unsigned int type,
error = gfs2_glock_get(sdp, no_addr, &gfs2_inode_glops, CREATE,
&ip->i_gl);
if (unlikely(error))
goto fail;
+
+ flush_work(&ip->i_gl->gl_final);
ip->i_gl->gl_object = ip;
error = gfs2_glock_get(sdp, no_addr, &gfs2_iopen_glops, CREATE,
&io_gl);
@@ -189,6 +191,7 @@ struct inode *gfs2_lookup_by_inum(struct gfs2_sbd *sdp, u64
no_addr,
if (error)
return ERR_PTR(error);
+ flush_work(&i_gh.gh_gl->gl_final);
error = gfs2_check_blk_type(sdp, no_addr, blktype);
if (error)
goto fail;
@@ -681,6 +684,7 @@ static int gfs2_create_inode(struct inode *dir, struct
dentry *dentry,
if (error)
goto fail_free_inode;
+ flush_work(&ip->i_gl->gl_final);
ip->i_gl->gl_object = ip;
error = gfs2_glock_nq_init(ip->i_gl, LM_ST_EXCLUSIVE, GL_SKIP, ghs + 1);
if (error)
