writeback: get rid of generic_sync_sb_inodes() export

This adds two new exported functions:

- writeback_inodes_sb(), which only attempts to writeback dirty inodes on
  this super_block, for WB_SYNC_NONE writeout.
- sync_inodes_sb(), which writes out all dirty inodes on this super_block
  and also waits for the IO to complete.

Acked-by: Jan Kara <jack@suse.cz>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

4 files changed, 55 insertions, 57 deletions

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index c54226be5294..271e5f44e871 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -458,8 +458,8 @@ writeback_single_inode(struct inode *inode, struct writeback_control *wbc)
  * on the writer throttling path, and we get decent balancing between many
  * throttled threads: we don't want them all piling up on inode_sync_wait.
  */
-void generic_sync_sb_inodes(struct super_block *sb,
-                                struct writeback_control *wbc)
+static void generic_sync_sb_inodes(struct super_block *sb,
+                                   struct writeback_control *wbc)
 {
         const unsigned long start = jiffies;    /* livelock avoidance */
         int sync = wbc->sync_mode == WB_SYNC_ALL;
@@ -593,13 +593,6 @@ void generic_sync_sb_inodes(struct super_block *sb,
 
         return;         /* Leave any unwritten inodes on s_io */
 }
-EXPORT_SYMBOL_GPL(generic_sync_sb_inodes);
-
-static void sync_sb_inodes(struct super_block *sb,
-                                struct writeback_control *wbc)
-{
-        generic_sync_sb_inodes(sb, wbc);
-}
 
 /*
  * Start writeback of dirty pagecache data against all unlocked inodes.
@@ -640,7 +633,7 @@ restart:
                          */
                         if (down_read_trylock(&sb->s_umount)) {
                                 if (sb->s_root)
-                                        sync_sb_inodes(sb, wbc);
+                                        generic_sync_sb_inodes(sb, wbc);
                                 up_read(&sb->s_umount);
                         }
                         spin_lock(&sb_lock);
@@ -653,35 +646,56 @@ restart:
         spin_unlock(&sb_lock);
 }
 
-/*
- * writeback and wait upon the filesystem's dirty inodes.  The caller will
- * do this in two passes - one to write, and one to wait.
- *
- * A finite limit is set on the number of pages which will be written.
- * To prevent infinite livelock of sys_sync().
+/**
+ * writeback_inodes_sb  -       writeback dirty inodes from given super_block
+ * @sb: the superblock
  *
- * We add in the number of potentially dirty inodes, because each inode write
- * can dirty pagecache in the underlying blockdev.
+ * Start writeback on some inodes on this super_block. No guarantees are made
+ * on how many (if any) will be written, and this function does not wait
+ * for IO completion of submitted IO. The number of pages submitted is
+ * returned.
  */
-void sync_inodes_sb(struct super_block *sb, int wait)
+long writeback_inodes_sb(struct super_block *sb)
 {
         struct writeback_control wbc = {
-                .sync_mode      = wait ? WB_SYNC_ALL : WB_SYNC_NONE,
+                .sync_mode      = WB_SYNC_NONE,
                 .range_start    = 0,
                 .range_end      = LLONG_MAX,
         };
+        unsigned long nr_dirty = global_page_state(NR_FILE_DIRTY);
+        unsigned long nr_unstable = global_page_state(NR_UNSTABLE_NFS);
+        long nr_to_write;
 
-        if (!wait) {
-                unsigned long nr_dirty = global_page_state(NR_FILE_DIRTY);
-                unsigned long nr_unstable = global_page_state(NR_UNSTABLE_NFS);
-
-                wbc.nr_to_write = nr_dirty + nr_unstable +
+        nr_to_write = nr_dirty + nr_unstable +
                         (inodes_stat.nr_inodes - inodes_stat.nr_unused);
-        } else
-                wbc.nr_to_write = LONG_MAX; /* doesn't actually matter */
 
-        sync_sb_inodes(sb, &wbc);
+        wbc.nr_to_write = nr_to_write;
+        generic_sync_sb_inodes(sb, &wbc);
+        return nr_to_write - wbc.nr_to_write;
+}
+EXPORT_SYMBOL(writeback_inodes_sb);
+
+/**
+ * sync_inodes_sb       -       sync sb inode pages
+ * @sb: the superblock
+ *
+ * This function writes and waits on any dirty inode belonging to this
+ * super_block. The number of pages synced is returned.
+ */
+long sync_inodes_sb(struct super_block *sb)
+{
+        struct writeback_control wbc = {
+                .sync_mode      = WB_SYNC_ALL,
+                .range_start    = 0,
+                .range_end      = LLONG_MAX,
+        };
+        long nr_to_write = LONG_MAX; /* doesn't actually matter */
+
+        wbc.nr_to_write = nr_to_write;
+        generic_sync_sb_inodes(sb, &wbc);
+        return nr_to_write - wbc.nr_to_write;
 }
+EXPORT_SYMBOL(sync_inodes_sb);
 
 /**
  * write_inode_now      -       write an inode to disk
diff --git a/fs/sync.c b/fs/sync.c
index 3422ba61d86d..66f210476f40 100644
--- a/fs/sync.c
+++ b/fs/sync.c
@@ -19,20 +19,22 @@
                         SYNC_FILE_RANGE_WAIT_AFTER)
 
 /*
- * Do the filesystem syncing work. For simple filesystems sync_inodes_sb(sb, 0)
- * just dirties buffers with inodes so we have to submit IO for these buffers
- * via __sync_blockdev(). This also speeds up the wait == 1 case since in that
- * case write_inode() functions do sync_dirty_buffer() and thus effectively
- * write one block at a time.
+ * Do the filesystem syncing work. For simple filesystems
+ * writeback_inodes_sb(sb) just dirties buffers with inodes so we have to
+ * submit IO for these buffers via __sync_blockdev(). This also speeds up the
+ * wait == 1 case since in that case write_inode() functions do
+ * sync_dirty_buffer() and thus effectively write one block at a time.
  */
 static int __sync_filesystem(struct super_block *sb, int wait)
 {
         /* Avoid doing twice syncing and cache pruning for quota sync */
-        if (!wait)
+        if (!wait) {
                 writeout_quota_sb(sb, -1);
-        else
+                writeback_inodes_sb(sb);
+        } else {
                 sync_quota_sb(sb, -1);
-        sync_inodes_sb(sb, wait);
+                sync_inodes_sb(sb);
+        }
         if (sb->s_op->sync_fs)
                 sb->s_op->sync_fs(sb, wait);
         return __sync_blockdev(sb->s_bdev, wait);
diff --git a/fs/ubifs/budget.c b/fs/ubifs/budget.c
index eaf6d891d46f..1c8991b0db13 100644
--- a/fs/ubifs/budget.c
+++ b/fs/ubifs/budget.c
@@ -65,26 +65,14 @@
 static int shrink_liability(struct ubifs_info *c, int nr_to_write)
 {
         int nr_written;
-        struct writeback_control wbc = {
-                .sync_mode   = WB_SYNC_NONE,
-                .range_end   = LLONG_MAX,
-                .nr_to_write = nr_to_write,
-        };
-
-        generic_sync_sb_inodes(c->vfs_sb, &wbc);
-        nr_written = nr_to_write - wbc.nr_to_write;
 
+        nr_written = writeback_inodes_sb(c->vfs_sb);
         if (!nr_written) {
                 /*
                  * Re-try again but wait on pages/inodes which are being
                  * written-back concurrently (e.g., by pdflush).
                  */
-                memset(&wbc, 0, sizeof(struct writeback_control));
-                wbc.sync_mode   = WB_SYNC_ALL;
-                wbc.range_end   = LLONG_MAX;
-                wbc.nr_to_write = nr_to_write;
-                generic_sync_sb_inodes(c->vfs_sb, &wbc);
-                nr_written = nr_to_write - wbc.nr_to_write;
+                nr_written = sync_inodes_sb(c->vfs_sb);
         }
 
         dbg_budg("%d pages were written back", nr_written);
diff --git a/fs/ubifs/super.c b/fs/ubifs/super.c
index 26d2e0d80465..8d6050a5966c 100644
--- a/fs/ubifs/super.c
+++ b/fs/ubifs/super.c
@@ -438,12 +438,6 @@ static int ubifs_sync_fs(struct super_block *sb, int wait)
 {
         int i, err;
         struct ubifs_info *c = sb->s_fs_info;
-        struct writeback_control wbc = {
-                .sync_mode   = WB_SYNC_ALL,
-                .range_start = 0,
-                .range_end   = LLONG_MAX,
-                .nr_to_write = LONG_MAX,
-        };
 
         /*
          * Zero @wait is just an advisory thing to help the file system shove
@@ -462,7 +456,7 @@ static int ubifs_sync_fs(struct super_block *sb, int wait)
          * the user be able to get more accurate results of 'statfs()' after
          * they synchronize the file system.
          */
-        generic_sync_sb_inodes(sb, &wbc);
+        sync_inodes_sb(sb);
 
         /*
          * Synchronize write buffers, because 'ubifs_run_commit()' does not