ext2: report metadata errors during fsync

When an IO error happens while writing metadata buffers, we should better
report it and call ext2_error since the filesystem is probably no longer
consistent.  Sometimes such IO errors happen while flushing thread does
background writeback, the buffer gets later evicted from memory, and thus
the only trace of the error remains as AS_EIO bit set in blockdevice's
mapping.  So we check this bit in ext2_fsync and report the error although
we cannot be really sure which buffer we failed to write.

Signed-off-by: Jan Kara <jack@suse.cz>
Cc: Chris Mason <chris.mason@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/ext2/dir.c

@@ -721,5 +721,5 @@ const struct file_operations ext2_dir_operations = {
 #ifdef CONFIG_COMPAT
 	.compat_ioctl	= ext2_compat_ioctl,
 #endif
-	.fsync		= simple_fsync,
+	.fsync		= ext2_fsync,
 };

fs/ext2/ext2.h

@@ -155,6 +155,7 @@ extern void ext2_write_super (struct super_block *);
 extern const struct file_operations ext2_dir_operations;
 
 /* file.c */
+extern int ext2_fsync(struct file *file, struct dentry *dentry, int datasync);
 extern const struct inode_operations ext2_file_inode_operations;
 extern const struct file_operations ext2_file_operations;
 extern const struct file_operations ext2_xip_file_operations;

fs/ext2/file.c

@@ -19,6 +19,7 @@
  */
 
 #include <linux/time.h>
+#include <linux/pagemap.h>
 #include "ext2.h"
 #include "xattr.h"
 #include "acl.h"
@@ -38,6 +39,22 @@ static int ext2_release_file (struct inode * inode, struct file * filp)
 	return 0;
 }
 
+int ext2_fsync(struct file *file, struct dentry *dentry, int datasync)
+{
+	int ret;
+	struct super_block *sb = dentry->d_inode->i_sb;
+	struct address_space *mapping = sb->s_bdev->bd_inode->i_mapping;
+
+	ret = simple_fsync(file, dentry, datasync);
+	if (ret == -EIO || test_and_clear_bit(AS_EIO, &mapping->flags)) {
+		/* We don't really know where the IO error happened... */
+		ext2_error(sb, __func__,
+			   "detected IO error when writing metadata buffers");
+		ret = -EIO;
+	}
+	return ret;
+}
+
 /*
  * We have mostly NULL's here: the current defaults are ok for
  * the ext2 filesystem.
@@ -55,7 +72,7 @@ const struct file_operations ext2_file_operations = {
 	.mmap		= generic_file_mmap,
 	.open		= generic_file_open,
 	.release	= ext2_release_file,
-	.fsync		= simple_fsync,
+	.fsync		= ext2_fsync,
 	.splice_read	= generic_file_splice_read,
 	.splice_write	= generic_file_splice_write,
 };
@@ -72,7 +89,7 @@ const struct file_operations ext2_xip_file_operations = {
 	.mmap		= xip_file_mmap,
 	.open		= generic_file_open,
 	.release	= ext2_release_file,
-	.fsync		= simple_fsync,
+	.fsync		= ext2_fsync,
 };
 #endif