fuse: introduce fc->bg_lock

To reduce contention of fc->lock, this patch introduces bg_lock for
protection of fields related to background queue. These are:
max_background, congestion_threshold, num_background, active_background,
bg_queue and blocked.

This allows next patch to make async reads not requiring fc->lock, so async
reads and writes will have better performance executed in parallel.

Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

5 files changed, 26 insertions, 15 deletions

diff --git a/fs/fuse/control.c b/fs/fuse/control.c
index eaa0e2b21623..989df5accaee 100644
--- a/fs/fuse/control.c
+++ b/fs/fuse/control.c
@@ -125,12 +125,12 @@ static ssize_t fuse_conn_max_background_write(struct file *file,
         if (ret > 0) {
                 struct fuse_conn *fc = fuse_ctl_file_conn_get(file);
                 if (fc) {
-                        spin_lock(&fc->lock);
+                        spin_lock(&fc->bg_lock);
                         fc->max_background = val;
                         fc->blocked = fc->num_background >= fc->max_background;
                         if (!fc->blocked)
                                 wake_up(&fc->blocked_waitq);
-                        spin_unlock(&fc->lock);
+                        spin_unlock(&fc->bg_lock);
                         fuse_conn_put(fc);
                 }
         }
@@ -171,7 +171,7 @@ static ssize_t fuse_conn_congestion_threshold_write(struct file *file,
         if (!fc)
                 goto out;
 
-        spin_lock(&fc->lock);
+        spin_lock(&fc->bg_lock);
         fc->congestion_threshold = val;
         if (fc->sb) {
                 if (fc->num_background < fc->congestion_threshold) {
@@ -182,7 +182,7 @@ static ssize_t fuse_conn_congestion_threshold_write(struct file *file,
                         set_bdi_congested(fc->sb->s_bdi, BLK_RW_ASYNC);
                 }
         }
-        spin_unlock(&fc->lock);
+        spin_unlock(&fc->bg_lock);
         fuse_conn_put(fc);
 out:
         return ret;
diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
index 6a7d3b4424e1..d4b9ffc6544d 100644
--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -287,10 +287,10 @@ void fuse_put_request(struct fuse_conn *fc, struct fuse_req *req)
                          * We get here in the unlikely case that a background
                          * request was allocated but not sent
                          */
-                        spin_lock(&fc->lock);
+                        spin_lock(&fc->bg_lock);
                         if (!fc->blocked)
                                 wake_up(&fc->blocked_waitq);
-                        spin_unlock(&fc->lock);
+                        spin_unlock(&fc->bg_lock);
                 }
 
                 if (test_bit(FR_WAITING, &req->flags)) {
@@ -390,7 +390,7 @@ static void request_end(struct fuse_conn *fc, struct fuse_req *req)
         WARN_ON(test_bit(FR_PENDING, &req->flags));
         WARN_ON(test_bit(FR_SENT, &req->flags));
         if (test_bit(FR_BACKGROUND, &req->flags)) {
-                spin_lock(&fc->lock);
+                spin_lock(&fc->bg_lock);
                 clear_bit(FR_BACKGROUND, &req->flags);
                 if (fc->num_background == fc->max_background) {
                         fc->blocked = 0;
@@ -413,7 +413,7 @@ static void request_end(struct fuse_conn *fc, struct fuse_req *req)
                 fc->num_background--;
                 fc->active_background--;
                 flush_bg_queue(fc);
-                spin_unlock(&fc->lock);
+                spin_unlock(&fc->bg_lock);
         }
         wake_up(&req->waitq);
         if (req->end)
@@ -586,8 +586,8 @@ ssize_t fuse_simple_request(struct fuse_conn *fc, struct fuse_args *args)
  *
  * fc->connected must have been checked previously
  */
-void fuse_request_send_background_locked(struct fuse_conn *fc,
-                                         struct fuse_req *req)
+void fuse_request_send_background_nocheck(struct fuse_conn *fc,
+                                          struct fuse_req *req)
 {
         BUG_ON(!test_bit(FR_BACKGROUND, &req->flags));
         if (!test_bit(FR_WAITING, &req->flags)) {
@@ -595,6 +595,7 @@ void fuse_request_send_background_locked(struct fuse_conn *fc,
                 atomic_inc(&fc->num_waiting);
         }
         __set_bit(FR_ISREPLY, &req->flags);
+        spin_lock(&fc->bg_lock);
         fc->num_background++;
         if (fc->num_background == fc->max_background)
                 fc->blocked = 1;
@@ -604,6 +605,7 @@ void fuse_request_send_background_locked(struct fuse_conn *fc,
         }
         list_add_tail(&req->list, &fc->bg_queue);
         flush_bg_queue(fc);
+        spin_unlock(&fc->bg_lock);
 }
 
 void fuse_request_send_background(struct fuse_conn *fc, struct fuse_req *req)
@@ -611,7 +613,7 @@ void fuse_request_send_background(struct fuse_conn *fc, struct fuse_req *req)
         BUG_ON(!req->end);
         spin_lock(&fc->lock);
         if (fc->connected) {
-                fuse_request_send_background_locked(fc, req);
+                fuse_request_send_background_nocheck(fc, req);
                 spin_unlock(&fc->lock);
         } else {
                 spin_unlock(&fc->lock);
@@ -2118,7 +2120,6 @@ void fuse_abort_conn(struct fuse_conn *fc, bool is_abort)
                 LIST_HEAD(to_end);
 
                 fc->connected = 0;
-                fc->blocked = 0;
                 fc->aborted = is_abort;
                 fuse_set_initialized(fc);
                 list_for_each_entry(fud, &fc->devices, entry) {
@@ -2140,8 +2141,11 @@ void fuse_abort_conn(struct fuse_conn *fc, bool is_abort)
                         list_splice_tail_init(&fpq->processing, &to_end);
                         spin_unlock(&fpq->lock);
                 }
+                spin_lock(&fc->bg_lock);
+                fc->blocked = 0;
                 fc->max_background = UINT_MAX;
                 flush_bg_queue(fc);
+                spin_unlock(&fc->bg_lock);
 
                 spin_lock(&fiq->waitq.lock);
                 fiq->connected = 0;
diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index 63136a2c23ab..65351d43c2b6 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -1502,7 +1502,7 @@ __acquires(fc->lock)
 
         req->in.args[1].size = inarg->size;
         fi->writectr++;
-        fuse_request_send_background_locked(fc, req);
+        fuse_request_send_background_nocheck(fc, req);
         return;
 
  out_free:
diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index 3e45d408a644..d6d55641a5a6 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -500,6 +500,10 @@ struct fuse_conn {
         /** The list of background requests set aside for later queuing */
         struct list_head bg_queue;
 
+        /** Protects: max_background, congestion_threshold, num_background,
+         * active_background, bg_queue, blocked */
+        spinlock_t bg_lock;
+
         /** Flag indicating that INIT reply has been received. Allocating
          * any fuse request will be suspended until the flag is set */
         int initialized;
@@ -860,8 +864,8 @@ ssize_t fuse_simple_request(struct fuse_conn *fc, struct fuse_args *args);
  */
 void fuse_request_send_background(struct fuse_conn *fc, struct fuse_req *req);
 
-void fuse_request_send_background_locked(struct fuse_conn *fc,
-                                         struct fuse_req *req);
+void fuse_request_send_background_nocheck(struct fuse_conn *fc,
+                                          struct fuse_req *req);
 
 /* Abort all requests */
 void fuse_abort_conn(struct fuse_conn *fc, bool is_abort);
diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
index db9e60b7eb69..ed3f49628ce2 100644
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -605,6 +605,7 @@ void fuse_conn_init(struct fuse_conn *fc, struct user_namespace *user_ns)
 {
         memset(fc, 0, sizeof(*fc));