fs: push i_mutex and filemap_write_and_wait down into ->fsync() handlers

Btrfs needs to be able to control how filemap_write_and_wait_range() is called
in fsync to make it less of a painful operation, so push down taking i_mutex and
the calling of filemap_write_and_wait() down into the ->fsync() handlers.  Some
file systems can drop taking the i_mutex altogether it seems, like ext3 and
ocfs2.  For correctness sake I just pushed everything down in all cases to make
sure that we keep the current behavior the same for everybody, and then each
individual fs maintainer can make up their mind about what to do from there.
Thanks,

Acked-by: Jan Kara <jack@suse.cz>
Signed-off-by: Josef Bacik <josef@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Conflicts:
	Documentation/filesystems/porting

Change-Id: I7697244cce355e6d443a39c5133a5c94f02e199b

5 files changed, 35 insertions, 11 deletions

diff --git a/drivers/char/ps3flash.c b/drivers/char/ps3flash.c
index 85c004a..bd29cd0 100644
--- a/drivers/char/ps3flash.c
+++ b/drivers/char/ps3flash.c
@@ -305,9 +305,14 @@ static int ps3flash_flush(struct file *file, fl_owner_t id)
 	return ps3flash_writeback(ps3flash_dev);
 }
 
-static int ps3flash_fsync(struct file *file, int datasync)
+static int ps3flash_fsync(struct file *file, loff_t start, loff_t end, int datasync)
 {
-	return ps3flash_writeback(ps3flash_dev);
+	struct inode *inode = file->f_path.dentry->d_inode;
+	int err;
+	mutex_lock(&inode->i_mutex);
+	err = ps3flash_writeback(ps3flash_dev);
+	mutex_unlock(&inode->i_mutex);
+	return err;
 }
 
 static irqreturn_t ps3flash_interrupt(int irq, void *data)
diff --git a/drivers/mtd/ubi/cdev.c b/drivers/mtd/ubi/cdev.c
index cdea669..ad76592 100644
--- a/drivers/mtd/ubi/cdev.c
+++ b/drivers/mtd/ubi/cdev.c
@@ -189,12 +189,16 @@ static loff_t vol_cdev_llseek(struct file *file, loff_t offset, int origin)
 	return new_offset;
 }
 
-static int vol_cdev_fsync(struct file *file, int datasync)
+static int vol_cdev_fsync(struct file *file, loff_t start, loff_t end, int datasync)
 {
 	struct ubi_volume_desc *desc = file->private_data;
 	struct ubi_device *ubi = desc->vol->ubi;
-
-	return ubi_sync(ubi->ubi_num);
+	struct inode *inode = file->f_path.dentry->d_inode;
+	int err;
+	mutex_lock(&inode->i_mutex);
+	err = ubi_sync(ubi->ubi_num);
+	mutex_unlock(&inode->i_mutex);
+	return err;
 }
 
 
diff --git a/drivers/staging/pohmelfs/inode.c b/drivers/staging/pohmelfs/inode.c
index c0f0ac7..f3c6060 100644
--- a/drivers/staging/pohmelfs/inode.c
+++ b/drivers/staging/pohmelfs/inode.c
@@ -887,11 +887,16 @@ static struct inode *pohmelfs_alloc_inode(struct super_block *sb)
 /*
  * We want fsync() to work on POHMELFS.
  */
-static int pohmelfs_fsync(struct file *file, int datasync)
+static int pohmelfs_fsync(struct file *file, loff_t start, loff_t end, int datasync)
 {
 	struct inode *inode = file->f_mapping->host;
-
-	return sync_inode_metadata(inode, 1);
+	int err = filemap_write_and_wait_range(inode->i_mapping, start, end);
+	if (!err) {
+		mutex_lock(&inode->i_mutex);
+		err = sync_inode_metadata(inode, 1);
+		mutex_unlock(&inode->i_mutex);
+	}
+	return err;
 }
 
 ssize_t pohmelfs_write(struct file *file, const char __user *buf,
diff --git a/drivers/usb/gadget/printer.c b/drivers/usb/gadget/printer.c
index 88a464c..9f6fd04 100644
--- a/drivers/usb/gadget/printer.c
+++ b/drivers/usb/gadget/printer.c
@@ -795,12 +795,14 @@ printer_write(struct file *fd, const char __user *buf, size_t len, loff_t *ptr)
 }
 
 static int
-printer_fsync(struct file *fd, int datasync)
+printer_fsync(struct file *fd, loff_t start, loff_t end, int datasync)
 {
 	struct printer_dev	*dev = fd->private_data;
+	struct inode *inode = fd->f_path.dentry->d_inode;
 	unsigned long		flags;
 	int			tx_list_empty;
 
+	mutex_lock(&inode->i_mutex);
 	spin_lock_irqsave(&dev->lock, flags);
 	tx_list_empty = (likely(list_empty(&dev->tx_reqs)));
 	spin_unlock_irqrestore(&dev->lock, flags);
@@ -810,6 +812,7 @@ printer_fsync(struct file *fd, int datasync)
 		wait_event_interruptible(dev->tx_flush_wait,
 				(likely(list_empty(&dev->tx_reqs_active))));
 	}
+	mutex_unlock(&inode->i_mutex);
 
 	return 0;
 }
diff --git a/drivers/video/fb_defio.c b/drivers/video/fb_defio.c
index 8040001..32814e8 100644
--- a/drivers/video/fb_defio.c
+++ b/drivers/video/fb_defio.c
@@ -66,19 +66,26 @@ static int fb_deferred_io_fault(struct vm_area_struct *vma,
 	return 0;
 }
 
-int fb_deferred_io_fsync(struct file *file, int datasync)
+int fb_deferred_io_fsync(struct file *file, loff_t start, loff_t end, int datasync)
 {
 	struct fb_info *info = file->private_data;
+	struct inode *inode = file->f_path.dentry->d_inode;
+	int err = filemap_write_and_wait_range(inode->i_mapping, start, end);
+	if (err)
+		return err;
 
 	/* Skip if deferred io is compiled-in but disabled on this fbdev */
 	if (!info->fbdefio)
 		return 0;
 
+	mutex_lock(&inode->i_mutex);
 	/* Kill off the delayed work */
 	cancel_delayed_work_sync(&info->deferred_work);
 
 	/* Run it immediately */
-	return schedule_delayed_work(&info->deferred_work, 0);
+	err = schedule_delayed_work(&info->deferred_work, 0);
+	mutex_unlock(&inode->i_mutex);
+	return err;
 }
 EXPORT_SYMBOL_GPL(fb_deferred_io_fsync);