Merge branch 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs-2.6

* 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs-2.6:
  ext3: Improve error message that changing journaling mode on remount is not possible
  ext3: Update Kconfig description of EXT3_DEFAULTS_TO_ORDERED

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;