fs/libfs.c: add generic data flush to fsync

Description by Jan Kara:
 "A lot of older filesystems don't properly flush volatile disk caches
  on fsync(2) which can lead to loss of fsynced data after power failure.

This patch makes generic_file_fsync() issue proper cache flush to fix the
problem.  Sysadmin can use /sys/devices/.../cache_type to tell the system
it should not send the cache flush."

[akpm@linux-foundation.org: nuke ifdef]
[akpm@linux-foundation.org: fix warning]
Signed-off-by: Fabian Frederick <fabf@skynet.be>
Suggested-by: Jan Kara <jack@suse.cz>
Suggested-by: Christoph Hellwig <hch@infradead.org>
Cc: Jan Kara <jack@suse.cz>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

3 files changed, 41 insertions, 3 deletions

diff --git a/fs/libfs.c b/fs/libfs.c
index a1844244246f..88e3e00e2eca 100644
--- a/fs/libfs.c
+++ b/fs/libfs.c
@@ -3,6 +3,7 @@
  *      Library for filesystems writers.
  */
 
+#include <linux/blkdev.h>
 #include <linux/export.h>
 #include <linux/pagemap.h>
 #include <linux/slab.h>
@@ -923,16 +924,19 @@ struct dentry *generic_fh_to_parent(struct super_block *sb, struct fid *fid,
 EXPORT_SYMBOL_GPL(generic_fh_to_parent);
 
 /**
- * generic_file_fsync - generic fsync implementation for simple filesystems
+ * __generic_file_fsync - generic fsync implementation for simple filesystems
+ *
  * @file:       file to synchronize
+ * @start:      start offset in bytes
+ * @end:        end offset in bytes (inclusive)
  * @datasync:   only synchronize essential metadata if true
  *
  * This is a generic implementation of the fsync method for simple
  * filesystems which track all non-inode metadata in the buffers list
  * hanging off the address_space structure.
  */
-int generic_file_fsync(struct file *file, loff_t start, loff_t end,
-                       int datasync)
+int __generic_file_fsync(struct file *file, loff_t start, loff_t end,
+                                 int datasync)
 {
         struct inode *inode = file->f_mapping->host;
         int err;
@@ -952,10 +956,34 @@ int generic_file_fsync(struct file *file, loff_t start, loff_t end,
         err = sync_inode_metadata(inode, 1);
         if (ret == 0)
                 ret = err;
+
 out:
         mutex_unlock(&inode->i_mutex);
         return ret;
 }
+EXPORT_SYMBOL(__generic_file_fsync);
+
+/**
+ * generic_file_fsync - generic fsync implementation for simple filesystems
+ *                      with flush
+ * @file:       file to synchronize
+ * @start:      start offset in bytes
+ * @end:        end offset in bytes (inclusive)
+ * @datasync:   only synchronize essential metadata if true
+ *
+ */
+
+int generic_file_fsync(struct file *file, loff_t start, loff_t end,
+                       int datasync)
+{
+        struct inode *inode = file->f_mapping->host;
+        int err;
+
+        err = __generic_file_fsync(file, start, end, datasync);
+        if (err)
+                return err;
+        return blkdev_issue_flush(inode->i_sb->s_bdev, GFP_KERNEL, NULL);
+}
 EXPORT_SYMBOL(generic_file_fsync);
 
 /**
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 8aba35f46f87..45cf6e537c83 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -1607,6 +1607,9 @@ struct block_device_operations {
 extern int __blkdev_driver_ioctl(struct block_device *, fmode_t, unsigned int,
                                  unsigned long);
 #else /* CONFIG_BLOCK */
+
+struct block_device;
+
 /*
  * stubs for when the block layer is configured out
  */
@@ -1642,6 +1645,12 @@ static inline bool blk_needs_flush_plug(struct task_struct *tsk)
         return false;
 }
 
+static inline int blkdev_issue_flush(struct block_device *bdev, gfp_t gfp_mask,
+                                     sector_t *error_sector)
+{
+        return 0;
+}
+
 #endif /* CONFIG_BLOCK */
 
 #endif
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 878031227c57..c3f46e499dd0 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2590,6 +2590,7 @@ extern ssize_t simple_read_from_buffer(void __user *to, size_t count,
 extern ssize_t simple_write_to_buffer(void *to, size_t available, loff_t *ppos,
                 const void __user *from, size_t count);
 
+extern int __generic_file_fsync(struct file *, loff_t, loff_t, int);
 extern int generic_file_fsync(struct file *, loff_t, loff_t, int);
 
 extern int generic_check_addressable(unsigned, u64);