f2fs: wake up discard_thread iff there is a candidate

This patch fixes to avoid needless wake ups.

Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

3 files changed, 27 insertions, 7 deletions

diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index 8306beace7cb..8375257b6b26 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -1494,8 +1494,7 @@ skip:
                 kmem_cache_free(discard_entry_slab, entry);
         }
 
-        dcc->discard_wake = 1;
-        wake_up_interruptible_all(&dcc->discard_wait_queue);
+        wake_up_discard_thread(sbi, false);
 }
 
 static int create_discard_cmd_control(struct f2fs_sb_info *sbi)
diff --git a/fs/f2fs/segment.h b/fs/f2fs/segment.h
index b9b4f85ffeb6..613b2fa7b1c1 100644
--- a/fs/f2fs/segment.h
+++ b/fs/f2fs/segment.h
@@ -798,3 +798,28 @@ static inline long nr_pages_to_write(struct f2fs_sb_info *sbi, int type,
         wbc->nr_to_write = desired;
         return desired - nr_to_write;
 }
+
+static inline void wake_up_discard_thread(struct f2fs_sb_info *sbi, bool force)
+{
+        struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info;
+        bool wakeup = false;
+        int i;
+
+        if (force)
+                goto wake_up;
+
+        mutex_lock(&dcc->cmd_lock);
+        for (i = MAX_PLIST_NUM - 1;
+                        i >= 0 && plist_issue(dcc->pend_list_tag[i]); i--) {
+                if (!list_empty(&dcc->pend_list[i])) {
+                        wakeup = true;
+                        break;
+                }
+        }
+        mutex_unlock(&dcc->cmd_lock);
+        if (!wakeup)
+                return;
+wake_up:
+        dcc->discard_wake = 1;
+        wake_up_interruptible_all(&dcc->discard_wait_queue);
+}
diff --git a/fs/f2fs/sysfs.c b/fs/f2fs/sysfs.c
index b9ad9041559f..962735dc9c63 100644
--- a/fs/f2fs/sysfs.c
+++ b/fs/f2fs/sysfs.c
@@ -178,13 +178,9 @@ static ssize_t f2fs_sbi_store(struct f2fs_attr *a,
         if (!strcmp(a->attr.name, "iostat_enable") && *ui == 0)
                 f2fs_reset_iostat(sbi);
         if (!strcmp(a->attr.name, "gc_urgent") && t == 1 && sbi->gc_thread) {
-                struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info;
-
                 sbi->gc_thread->gc_wake = 1;
                 wake_up_interruptible_all(&sbi->gc_thread->gc_wait_queue_head);
-
-                dcc->discard_wake = 1;
-                wake_up_interruptible_all(&dcc->discard_wait_queue);
+                wake_up_discard_thread(sbi, true);
         }
 
         return count;