ext4: Add delayed allocation support in data=writeback mode

Updated with fixes from Mingming Cao <cmm@us.ibm.com> to unlock and
release the page from page cache if the delalloc write_begin failed, and
properly handle preallocated blocks.  Also added a fix to clear
buffer_delay in block_write_full_page() after allocating a delayed
buffer.

Updated with fixes from Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
to update i_disksize properly and to add bmap support for delayed
allocation.

Updated with a fix from Valerie Clement <valerie.clement@bull.net> to
avoid filesystem corruption when the filesystem is mounted with the
delalloc option and blocksize < pagesize.

Signed-off-by: Alex Tomas <alex@clusterfs.com>
Signed-off-by: Mingming Cao <cmm@us.ibm.com>
Signed-off-by: Dave Kleikamp <shaggy@linux.vnet.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by:  Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>

1 files changed, 5 insertions, 1 deletions

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 629d0fa27e3a..de9d3d0eb203 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -898,7 +898,7 @@ enum {
         Opt_jqfmt_vfsold, Opt_jqfmt_vfsv0, Opt_quota, Opt_noquota,
         Opt_ignore, Opt_barrier, Opt_err, Opt_resize, Opt_usrquota,
         Opt_grpquota, Opt_extents, Opt_noextents, Opt_i_version,
-        Opt_mballoc, Opt_nomballoc, Opt_stripe,
+        Opt_mballoc, Opt_nomballoc, Opt_stripe, Opt_delalloc,
 };
 
 static match_table_t tokens = {
@@ -957,6 +957,7 @@ static match_table_t tokens = {
         {Opt_nomballoc, "nomballoc"},
         {Opt_stripe, "stripe=%u"},
         {Opt_resize, "resize"},
+        {Opt_delalloc, "delalloc"},
         {Opt_err, NULL},
 };
 
@@ -1335,6 +1336,9 @@ set_qf_format:
                                 return 0;
                         sbi->s_stripe = option;
                         break;
+                case Opt_delalloc:
+                        set_opt(sbi->s_mount_opt, DELALLOC);
+                        break;
                 default:
                         printk (KERN_ERR
                                 "EXT4-fs: Unrecognized mount option \"%s\" "