2 files changed, 45 insertions, 10 deletions

diff --git a/Documentation/filesystems/ext4.txt b/Documentation/filesystems/ext4.txt
index 5c484aec2ba..97882df0486 100644
--- a/Documentation/filesystems/ext4.txt
+++ b/Documentation/filesystems/ext4.txt
@@ -183,8 +183,8 @@ commit=nrsec	(*)	Ext4 can be told to sync all its data and metadata
                         performance.
 
 barrier=<0|1(*)>        This enables/disables the use of write barriers in
-                        the jbd code.  barrier=0 disables, barrier=1 enables.
-                        This also requires an IO stack which can support
+barrier(*)              the jbd code.  barrier=0 disables, barrier=1 enables.
+nobarrier               This also requires an IO stack which can support
                         barriers, and if jbd gets an error on a barrier
                         write, it will disable again with a warning.
                         Write barriers enforce proper on-disk ordering
@@ -192,6 +192,9 @@ barrier=<0|1(*)>	This enables/disables the use of write barriers in
                         safe to use, at some performance penalty.  If
                         your disks are battery-backed in one way or another,
                         disabling barriers may safely improve performance.
+                        The mount options "barrier" and "nobarrier" can
+                        also be used to enable or disable barriers, for
+                        consistency with other ext4 mount options.
 
 inode_readahead=n       This tuning parameter controls the maximum
                         number of inode table blocks that ext4's inode
@@ -313,6 +316,24 @@ journal_ioprio=prio	The I/O priority (from 0 to 7, where 0 is the
                         a slightly higher priority than the default I/O
                         priority.
 
+auto_da_alloc(*)        Many broken applications don't use fsync() when 
+noauto_da_alloc         replacing existing files via patterns such as
+                        fd = open("foo.new")/write(fd,..)/close(fd)/
+                        rename("foo.new", "foo"), or worse yet,
+                        fd = open("foo", O_TRUNC)/write(fd,..)/close(fd).
+                        If auto_da_alloc is enabled, ext4 will detect
+                        the replace-via-rename and replace-via-truncate
+                        patterns and force that any delayed allocation
+                        blocks are allocated such that at the next
+                        journal commit, in the default data=ordered
+                        mode, the data blocks of the new file are forced
+                        to disk before the rename() operation is
+                        commited.  This provides roughly the same level
+                        of guarantees as ext3, and avoids the
+                        "zero-length" problem that can happen when a
+                        system crashes before the delayed allocation
+                        blocks are forced to disk.
+
 Data Mode
 =========
 There are 3 different data modes:
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 45d07cf9df3..9987bba99db 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -867,7 +867,7 @@ static int ext4_show_options(struct seq_file *seq, struct vfsmount *vfs)
                 seq_puts(seq, ",data_err=abort");
 
         if (test_opt(sb, NO_AUTO_DA_ALLOC))
-                seq_puts(seq, ",auto_da_alloc=0");
+                seq_puts(seq, ",noauto_da_alloc");
 
         ext4_show_quota_options(seq, sb);
         return 0;
@@ -1018,7 +1018,7 @@ enum {
         Opt_resgid, Opt_resuid, Opt_sb, Opt_err_cont, Opt_err_panic, Opt_err_ro,
         Opt_nouid32, Opt_debug, Opt_oldalloc, Opt_orlov,
         Opt_user_xattr, Opt_nouser_xattr, Opt_acl, Opt_noacl,
-        Opt_auto_da_alloc, Opt_noload, Opt_nobh, Opt_bh,
+        Opt_auto_da_alloc, Opt_noauto_da_alloc, Opt_noload, Opt_nobh, Opt_bh,
         Opt_commit, Opt_min_batch_time, Opt_max_batch_time,
         Opt_journal_update, Opt_journal_dev,
         Opt_journal_checksum, Opt_journal_async_commit,
@@ -1026,8 +1026,8 @@ enum {
         Opt_data_err_abort, Opt_data_err_ignore,
         Opt_usrjquota, Opt_grpjquota, Opt_offusrjquota, Opt_offgrpjquota,
         Opt_jqfmt_vfsold, Opt_jqfmt_vfsv0, Opt_quota, Opt_noquota,
-        Opt_ignore, Opt_barrier, Opt_err, Opt_resize, Opt_usrquota,
-        Opt_grpquota, Opt_i_version,
+        Opt_ignore, Opt_barrier, Opt_nobarrier, Opt_err, Opt_resize,
+        Opt_usrquota, Opt_grpquota, Opt_i_version,
         Opt_stripe, Opt_delalloc, Opt_nodelalloc,
         Opt_inode_readahead_blks, Opt_journal_ioprio
 };
@@ -1080,6 +1080,8 @@ static const match_table_t tokens = {
         {Opt_quota, "quota"},
         {Opt_usrquota, "usrquota"},
         {Opt_barrier, "barrier=%u"},
+        {Opt_barrier, "barrier"},
+        {Opt_nobarrier, "nobarrier"},
         {Opt_i_version, "i_version"},
         {Opt_stripe, "stripe=%u"},
         {Opt_resize, "resize"},
@@ -1088,6 +1090,8 @@ static const match_table_t tokens = {
         {Opt_inode_readahead_blks, "inode_readahead_blks=%u"},
         {Opt_journal_ioprio, "journal_ioprio=%u"},
         {Opt_auto_da_alloc, "auto_da_alloc=%u"},
+        {Opt_auto_da_alloc, "auto_da_alloc"},
+        {Opt_noauto_da_alloc, "noauto_da_alloc"},
         {Opt_err, NULL},
 };
 
@@ -1422,9 +1426,14 @@ set_qf_format:
                 case Opt_abort:
                         set_opt(sbi->s_mount_opt, ABORT);
                         break;
+                case Opt_nobarrier:
+                        clear_opt(sbi->s_mount_opt, BARRIER);
+                        break;
                 case Opt_barrier:
-                        if (match_int(&args[0], &option))
-                                return 0;
+                        if (match_int(&args[0], &option)) {
+                                set_opt(sbi->s_mount_opt, BARRIER);
+                                break;
+                        }
                         if (option)
                                 set_opt(sbi->s_mount_opt, BARRIER);
                         else
@@ -1485,9 +1494,14 @@ set_qf_format:
                         *journal_ioprio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_BE,
                                                             option);
                         break;
+                case Opt_noauto_da_alloc:
+                        set_opt(sbi->s_mount_opt,NO_AUTO_DA_ALLOC);
+                        break;
                 case Opt_auto_da_alloc:
-                        if (match_int(&args[0], &option))
-                                return 0;
+                        if (match_int(&args[0], &option)) {
+                                clear_opt(sbi->s_mount_opt, NO_AUTO_DA_ALLOC);
+                                break;
+                        }
                         if (option)
                                 clear_opt(sbi->s_mount_opt, NO_AUTO_DA_ALLOC);
                         else