ext4: enable barriers by default

I can't think of any valid reason for ext4 to not use barriers when
they are available;  I believe this is necessary for filesystem
integrity in the face of a volatile write cache on storage.

An administrator who trusts that the cache is sufficiently battery-
backed (and power supplies are sufficiently redundant, etc...)
can always turn it back off again.

SuSE has carried such a patch for ext3 for quite some time now.

Also document the mount option while we're at it.

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: Mingming Cao <cmm@us.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

1 files changed, 9 insertions, 2 deletions

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index ba92c606ad9a..cb96f127c366 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -671,6 +671,7 @@ static int ext4_show_options(struct seq_file *seq, struct vfsmount *vfs)
         unsigned long def_mount_opts;
         struct super_block *sb = vfs->mnt_sb;
         struct ext4_sb_info *sbi = EXT4_SB(sb);
+        journal_t *journal = sbi->s_journal;
         struct ext4_super_block *es = sbi->s_es;
 
         def_mount_opts = le32_to_cpu(es->s_default_mount_opts);
@@ -729,8 +730,13 @@ static int ext4_show_options(struct seq_file *seq, struct vfsmount *vfs)
                 seq_printf(seq, ",commit=%u",
                            (unsigned) (sbi->s_commit_interval / HZ));
         }
-        if (test_opt(sb, BARRIER))
-                seq_puts(seq, ",barrier=1");
+        /*
+         * We're changing the default of barrier mount option, so
+         * let's always display its mount state so it's clear what its
+         * status is.
+         */
+        seq_puts(seq, ",barrier=");
+        seq_puts(seq, test_opt(sb, BARRIER) ? "1" : "0");
         if (test_opt(sb, JOURNAL_ASYNC_COMMIT))
                 seq_puts(seq, ",journal_async_commit");
         if (test_opt(sb, NOBH))
@@ -1909,6 +1915,7 @@ static int ext4_fill_super (struct super_block *sb, void *data, int silent)
         sbi->s_resgid = le16_to_cpu(es->s_def_resgid);
 
         set_opt(sbi->s_mount_opt, RESERVATION);
+        set_opt(sbi->s_mount_opt, BARRIER);
 
         /*
          * turn on extents feature by default in ext4 filesystem