1 files changed, 66 insertions, 19 deletions

diff --git a/fs/sync.c b/fs/sync.c
index 3422ba61d86d..c08467a5d7cb 100644
--- a/fs/sync.c
+++ b/fs/sync.c
@@ -19,20 +19,29 @@
                         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)
 {
+        /*
+         * This should be safe, as we require bdi backing to actually
+         * write out data in the first place
+         */
+        if (!sb->s_bdi)
+                return 0;
+
         /* 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);
@@ -99,7 +108,7 @@ restart:
                 spin_unlock(&sb_lock);
 
                 down_read(&sb->s_umount);
-                if (!(sb->s_flags & MS_RDONLY) && sb->s_root)
+                if (!(sb->s_flags & MS_RDONLY) && sb->s_root && sb->s_bdi)
                         __sync_filesystem(sb, wait);
                 up_read(&sb->s_umount);
 
@@ -118,7 +127,7 @@ restart:
  */
 SYSCALL_DEFINE0(sync)
 {
-        wakeup_pdflush(0);
+        wakeup_flusher_threads(0);
         sync_filesystems(0);
         sync_filesystems(1);
         if (unlikely(laptop_mode))
@@ -176,19 +185,23 @@ int file_fsync(struct file *filp, struct dentry *dentry, int datasync)
 }
 
 /**
- * vfs_fsync - perform a fsync or fdatasync on a file
+ * vfs_fsync_range - helper to sync a range of data & metadata to disk
  * @file:               file to sync
  * @dentry:             dentry of @file
- * @data:               only perform a fdatasync operation
+ * @start:              offset in bytes of the beginning of data range to sync
+ * @end:                offset in bytes of the end of data range (inclusive)
+ * @datasync:           perform only datasync
  *
- * Write back data and metadata for @file to disk.  If @datasync is
- * set only metadata needed to access modified file data is written.
+ * Write back data in range @start..@end and metadata for @file to disk.  If
+ * @datasync is set only metadata needed to access modified file data is
+ * written.
  *
  * In case this function is called from nfsd @file may be %NULL and
  * only @dentry is set.  This can only happen when the filesystem
  * implements the export_operations API.
  */
-int vfs_fsync(struct file *file, struct dentry *dentry, int datasync)
+int vfs_fsync_range(struct file *file, struct dentry *dentry, loff_t start,
+                    loff_t end, int datasync)
 {
         const struct file_operations *fop;
         struct address_space *mapping;
@@ -212,7 +225,7 @@ int vfs_fsync(struct file *file, struct dentry *dentry, int datasync)
                 goto out;
         }
 
-        ret = filemap_fdatawrite(mapping);
+        ret = filemap_write_and_wait_range(mapping, start, end);
 
         /*
          * We need to protect against concurrent writers, which could cause
@@ -223,12 +236,29 @@ int vfs_fsync(struct file *file, struct dentry *dentry, int datasync)
         if (!ret)
                 ret = err;
         mutex_unlock(&mapping->host->i_mutex);
-        err = filemap_fdatawait(mapping);
-        if (!ret)
-                ret = err;
+
 out:
         return ret;
 }
+EXPORT_SYMBOL(vfs_fsync_range);
+
+/**
+ * vfs_fsync - perform a fsync or fdatasync on a file
+ * @file:               file to sync
+ * @dentry:             dentry of @file
+ * @datasync:           only perform a fdatasync operation
+ *
+ * Write back data and metadata for @file to disk.  If @datasync is
+ * set only metadata needed to access modified file data is written.
+ *
+ * In case this function is called from nfsd @file may be %NULL and
+ * only @dentry is set.  This can only happen when the filesystem
+ * implements the export_operations API.
+ */
+int vfs_fsync(struct file *file, struct dentry *dentry, int datasync)
+{
+        return vfs_fsync_range(file, dentry, 0, LLONG_MAX, datasync);
+}
 EXPORT_SYMBOL(vfs_fsync);
 
 static int do_fsync(unsigned int fd, int datasync)
@@ -254,6 +284,23 @@ SYSCALL_DEFINE1(fdatasync, unsigned int, fd)
         return do_fsync(fd, 1);
 }
 
+/**
+ * generic_write_sync - perform syncing after a write if file / inode is sync
+ * @file:       file to which the write happened
+ * @pos:        offset where the write started
+ * @count:      length of the write
+ *
+ * This is just a simple wrapper about our general syncing function.
+ */
+int generic_write_sync(struct file *file, loff_t pos, loff_t count)
+{
+        if (!(file->f_flags & O_SYNC) && !IS_SYNC(file->f_mapping->host))
+                return 0;
+        return vfs_fsync_range(file, file->f_path.dentry, pos,
+                               pos + count - 1, 1);
+}
+EXPORT_SYMBOL(generic_write_sync);
+
 /*
  * sys_sync_file_range() permits finely controlled syncing over a segment of
  * a file in the range offset .. (offset+nbytes-1) inclusive.  If nbytes is