f2fs: add the flush_merge handle in the remount flow

Add the *remount* handle of flush_merge option, so that the users
can enable flush_merge in the runtime, such as the underlying device
handles the cache_flush command relatively slowly.

Signed-off-by: Gu Zheng <guz.fnst@cn.fujitsu.com>
Signed-off-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>

3 files changed, 45 insertions, 3 deletions

diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index d3180f8c0f97..55152de1118c 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -1177,6 +1177,7 @@ void destroy_node_manager_caches(void);
  */
 void f2fs_balance_fs(struct f2fs_sb_info *);
 void f2fs_balance_fs_bg(struct f2fs_sb_info *);
+int issue_flush_thread(void *);
 int f2fs_issue_flush(struct f2fs_sb_info *);
 void invalidate_blocks(struct f2fs_sb_info *, block_t);
 void refresh_sit_entry(struct f2fs_sb_info *, block_t, block_t);
diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index 9993f94848fc..f6816e18db98 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -197,7 +197,7 @@ void f2fs_balance_fs_bg(struct f2fs_sb_info *sbi)
                 f2fs_sync_fs(sbi->sb, true);
 }
 
-static int issue_flush_thread(void *data)
+int issue_flush_thread(void *data)
 {
         struct f2fs_sb_info *sbi = data;
         struct f2fs_sm_info *sm_i = SM_I(sbi);
diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
index 5e20d2a36eac..bea642aec0fe 100644
--- a/fs/f2fs/super.c
+++ b/fs/f2fs/super.c
@@ -594,6 +594,8 @@ static int f2fs_remount(struct super_block *sb, int *flags, char *data)
         struct f2fs_sb_info *sbi = F2FS_SB(sb);
         struct f2fs_mount_info org_mount_opt;
         int err, active_logs;
+        bool need_restart_gc = false;
+        bool need_stop_gc = false;
 
         sync_filesystem(sb);
 
@@ -611,7 +613,7 @@ static int f2fs_remount(struct super_block *sb, int *flags, char *data)
 
         /*
          * Previous and new state of filesystem is RO,
-         * so no point in checking GC conditions.
+         * so skip checking GC and FLUSH_MERGE conditions.
          */
         if ((sb->s_flags & MS_RDONLY) && (*flags & MS_RDONLY))
                 goto skip;
@@ -625,18 +627,57 @@ static int f2fs_remount(struct super_block *sb, int *flags, char *data)
                 if (sbi->gc_thread) {
                         stop_gc_thread(sbi);
                         f2fs_sync_fs(sb, 1);
+                        need_restart_gc = true;
                 }
         } else if (test_opt(sbi, BG_GC) && !sbi->gc_thread) {
                 err = start_gc_thread(sbi);
                 if (err)
                         goto restore_opts;
+                need_stop_gc = true;
+        }
+
+        /*
+         * We stop issue flush thread if FS is mounted as RO
+         * or if flush_merge is not passed in mount option.
+         */
+        if ((*flags & MS_RDONLY) || !test_opt(sbi, FLUSH_MERGE)) {
+                struct f2fs_sm_info *sm_info = sbi->sm_info;
+
+                if (sm_info->f2fs_issue_flush)
+                        kthread_stop(sm_info->f2fs_issue_flush);
+                sm_info->issue_list = sm_info->dispatch_list = NULL;
+                sm_info->f2fs_issue_flush = NULL;
+        } else if (test_opt(sbi, FLUSH_MERGE)) {
+                struct f2fs_sm_info *sm_info = sbi->sm_info;
+
+                if (!sm_info->f2fs_issue_flush) {
+                        dev_t dev = sbi->sb->s_bdev->bd_dev;
+
+                        spin_lock_init(&sm_info->issue_lock);
+                        init_waitqueue_head(&sm_info->flush_wait_queue);
+                        sm_info->f2fs_issue_flush =
+                                kthread_run(issue_flush_thread, sbi,
+                                "f2fs_flush-%u:%u", MAJOR(dev), MINOR(dev));
+                        if (IS_ERR(sm_info->f2fs_issue_flush)) {
+                                err = PTR_ERR(sm_info->f2fs_issue_flush);
+                                sm_info->f2fs_issue_flush = NULL;
+                                goto restore_gc;
+                        }
+                }
         }
 skip:
         /* Update the POSIXACL Flag */
          sb->s_flags = (sb->s_flags & ~MS_POSIXACL) |
                 (test_opt(sbi, POSIX_ACL) ? MS_POSIXACL : 0);
         return 0;
-
+restore_gc:
+        if (need_restart_gc) {
+                if (start_gc_thread(sbi))
+                        f2fs_msg(sbi->sb, KERN_WARNING,
+                                "background gc thread is stop");
+        } else if (need_stop_gc) {
+                stop_gc_thread(sbi);
+        }
 restore_opts:
         sbi->mount_opt = org_mount_opt;
         sbi->active_logs = active_logs;