2 files changed, 44 insertions, 28 deletions

diff --git a/fs/ext3/Kconfig b/fs/ext3/Kconfig
index fb3c1a21b135..522b15498f45 100644
--- a/fs/ext3/Kconfig
+++ b/fs/ext3/Kconfig
@@ -29,23 +29,25 @@ config EXT3_FS
           module will be called ext3.
 
 config EXT3_DEFAULTS_TO_ORDERED
-        bool "Default to 'data=ordered' in ext3 (legacy option)"
+        bool "Default to 'data=ordered' in ext3"
         depends on EXT3_FS
         help
-          If a filesystem does not explicitly specify a data ordering
-          mode, and the journal capability allowed it, ext3 used to
-          historically default to 'data=ordered'.
-
-          That was a rather unfortunate choice, because it leads to all
-          kinds of latency problems, and the 'data=writeback' mode is more
-          appropriate these days.
-
-          You should probably always answer 'n' here, and if you really
-          want to use 'data=ordered' mode, set it in the filesystem itself
-          with 'tune2fs -o journal_data_ordered'.
-
-          But if you really want to enable the legacy default, you can do
-          so by answering 'y' to this question.
+          The journal mode options for ext3 have different tradeoffs
+          between when data is guaranteed to be on disk and
+          performance.  The use of "data=writeback" can cause
+          unwritten data to appear in files after an system crash or
+          power failure, which can be a security issue.  However,
+          "data=ordered" mode can also result in major performance
+          problems, including seconds-long delays before an fsync()
+          call returns.  For details, see:
+
+          http://ext4.wiki.kernel.org/index.php/Ext3_data_mode_tradeoffs
+
+          If you have been historically happy with ext3's performance,
+          data=ordered mode will be a safe choice and you should
+          answer 'y' here.  If you understand the reliability and data
+          privacy issues of data=writeback and are willing to make
+          that trade off, answer 'n'.
 
 config EXT3_FS_XATTR
         bool "Ext3 extended attributes"
diff --git a/fs/ext3/super.c b/fs/ext3/super.c
index 524b349c6299..a8d80a7f1105 100644
--- a/fs/ext3/super.c
+++ b/fs/ext3/super.c
@@ -543,6 +543,19 @@ static inline void ext3_show_quota_options(struct seq_file *seq, struct super_bl
 #endif
 }
 
+static char *data_mode_string(unsigned long mode)
+{
+        switch (mode) {
+        case EXT3_MOUNT_JOURNAL_DATA:
+                return "journal";
+        case EXT3_MOUNT_ORDERED_DATA:
+                return "ordered";
+        case EXT3_MOUNT_WRITEBACK_DATA:
+                return "writeback";
+        }
+        return "unknown";
+}
+
 /*
  * Show an option if
  *  - it's set to a non-default value OR
@@ -616,13 +629,8 @@ static int ext3_show_options(struct seq_file *seq, struct vfsmount *vfs)
         if (test_opt(sb, NOBH))
                 seq_puts(seq, ",nobh");
 
-        if (test_opt(sb, DATA_FLAGS) == EXT3_MOUNT_JOURNAL_DATA)
-                seq_puts(seq, ",data=journal");
-        else if (test_opt(sb, DATA_FLAGS) == EXT3_MOUNT_ORDERED_DATA)
-                seq_puts(seq, ",data=ordered");
-        else if (test_opt(sb, DATA_FLAGS) == EXT3_MOUNT_WRITEBACK_DATA)
-                seq_puts(seq, ",data=writeback");
-
+        seq_printf(seq, ",data=%s", data_mode_string(sbi->s_mount_opt &
+                                                     EXT3_MOUNT_DATA_FLAGS));
         if (test_opt(sb, DATA_ERR_ABORT))
                 seq_puts(seq, ",data_err=abort");
 
@@ -1024,12 +1032,18 @@ static int parse_options (char *options, struct super_block *sb,
                 datacheck:
                         if (is_remount) {
                                 if ((sbi->s_mount_opt & EXT3_MOUNT_DATA_FLAGS)
-                                                != data_opt) {
-                                        printk(KERN_ERR
-                                                "EXT3-fs: cannot change data "
-                                                "mode on remount\n");
-                                        return 0;
-                                }
+                                                == data_opt)
+                                        break;
+                                printk(KERN_ERR
+                                        "EXT3-fs (device %s): Cannot change "
+                                        "data mode on remount. The filesystem "
+                                        "is mounted in data=%s mode and you "
+                                        "try to remount it in data=%s mode.\n",
+                                        sb->s_id,
+                                        data_mode_string(sbi->s_mount_opt &
+                                                        EXT3_MOUNT_DATA_FLAGS),
+                                        data_mode_string(data_opt));
+                                return 0;
                         } else {
                                 sbi->s_mount_opt &= ~EXT3_MOUNT_DATA_FLAGS;
                                 sbi->s_mount_opt |= data_opt;