4 files changed, 52 insertions, 2 deletions

diff --git a/Documentation/filesystems/ocfs2.txt b/Documentation/filesystems/ocfs2.txt
index 1f7ae144f6d8..5393e6611691 100644
--- a/Documentation/filesystems/ocfs2.txt
+++ b/Documentation/filesystems/ocfs2.txt
@@ -87,3 +87,10 @@ dir_resv_level=	(*)	By default, directory reservations will scale with file
                         reservations - users should rarely need to change this
                         value. If allocation reservations are turned off, this
                         option will have no effect.
+coherency=full  (*)     Disallow concurrent O_DIRECT writes, cluster inode
+                        lock will be taken to force other nodes drop cache,
+                        therefore full cluster coherency is guaranteed even
+                        for O_DIRECT writes.
+coherency=buffered      Allow concurrent O_DIRECT writes without EX lock among
+                        nodes, which gains high performance at risk of getting
+                        stale data on other nodes.
diff --git a/fs/ocfs2/file.c b/fs/ocfs2/file.c
index 13af9937bdda..9e8cc4346b76 100644
--- a/fs/ocfs2/file.c
+++ b/fs/ocfs2/file.c
@@ -2225,6 +2225,8 @@ static ssize_t ocfs2_file_aio_write(struct kiocb *iocb,
         struct file *file = iocb->ki_filp;
         struct inode *inode = file->f_path.dentry->d_inode;
         struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
+        int full_coherency = !(osb->s_mount_opt &
+                               OCFS2_MOUNT_COHERENCY_BUFFERED);
 
         mlog_entry("(0x%p, %u, '%.*s')\n", file,
                    (unsigned int)nr_segs,
@@ -2248,14 +2250,37 @@ relock:
                 have_alloc_sem = 1;
         }
 
-        /* concurrent O_DIRECT writes are allowed */
-        rw_level = !direct_io;
+        /*
+         * Concurrent O_DIRECT writes are allowed with
+         * mount_option "coherency=buffered".
+         */
+        rw_level = (!direct_io || full_coherency);
+
         ret = ocfs2_rw_lock(inode, rw_level);
         if (ret < 0) {
                 mlog_errno(ret);
                 goto out_sems;
         }
 
+        /*
+         * O_DIRECT writes with "coherency=full" need to take EX cluster
+         * inode_lock to guarantee coherency.
+         */
+        if (direct_io && full_coherency) {
+                /*
+                 * We need to take and drop the inode lock to force
+                 * other nodes to drop their caches.  Buffered I/O
+                 * already does this in write_begin().
+                 */
+                ret = ocfs2_inode_lock(inode, NULL, 1);
+                if (ret < 0) {
+                        mlog_errno(ret);
+                        goto out_sems;
+                }
+
+                ocfs2_inode_unlock(inode, 1);
+        }
+
         can_do_direct = direct_io;
         ret = ocfs2_prepare_inode_for_write(file, ppos,
                                             iocb->ki_left, appending,
diff --git a/fs/ocfs2/ocfs2.h b/fs/ocfs2/ocfs2.h
index 687e291d73f2..3064feef1430 100644
--- a/fs/ocfs2/ocfs2.h
+++ b/fs/ocfs2/ocfs2.h
@@ -263,6 +263,9 @@ enum ocfs2_mount_options
                                                    control lists */
         OCFS2_MOUNT_USRQUOTA = 1 << 10, /* We support user quotas */
         OCFS2_MOUNT_GRPQUOTA = 1 << 11, /* We support group quotas */
+
+        OCFS2_MOUNT_COHERENCY_BUFFERED = 1 << 12 /* Allow concurrent O_DIRECT
+                                                    writes */
 };
 
 #define OCFS2_OSB_SOFT_RO                       0x0001
diff --git a/fs/ocfs2/super.c b/fs/ocfs2/super.c
index b578644b6637..9122d59f8127 100644
--- a/fs/ocfs2/super.c
+++ b/fs/ocfs2/super.c
@@ -177,6 +177,8 @@ enum {
         Opt_noacl,
         Opt_usrquota,
         Opt_grpquota,
+        Opt_coherency_buffered,
+        Opt_coherency_full,
         Opt_resv_level,
         Opt_dir_resv_level,
         Opt_err,
@@ -205,6 +207,8 @@ static const match_table_t tokens = {
         {Opt_noacl, "noacl"},
         {Opt_usrquota, "usrquota"},
         {Opt_grpquota, "grpquota"},
+        {Opt_coherency_buffered, "coherency=buffered"},
+        {Opt_coherency_full, "coherency=full"},
         {Opt_resv_level, "resv_level=%u"},
         {Opt_dir_resv_level, "dir_resv_level=%u"},
         {Opt_err, NULL}
@@ -1452,6 +1456,12 @@ static int ocfs2_parse_options(struct super_block *sb,
                 case Opt_grpquota:
                         mopt->mount_opt |= OCFS2_MOUNT_GRPQUOTA;
                         break;
+                case Opt_coherency_buffered:
+                        mopt->mount_opt |= OCFS2_MOUNT_COHERENCY_BUFFERED;
+                        break;
+                case Opt_coherency_full:
+                        mopt->mount_opt &= ~OCFS2_MOUNT_COHERENCY_BUFFERED;
+                        break;
                 case Opt_acl:
                         mopt->mount_opt |= OCFS2_MOUNT_POSIX_ACL;
                         mopt->mount_opt &= ~OCFS2_MOUNT_NO_POSIX_ACL;
@@ -1550,6 +1560,11 @@ static int ocfs2_show_options(struct seq_file *s, struct vfsmount *mnt)
         if (opts & OCFS2_MOUNT_GRPQUOTA)
                 seq_printf(s, ",grpquota");
 
+        if (opts & OCFS2_MOUNT_COHERENCY_BUFFERED)
+                seq_printf(s, ",coherency=buffered");
+        else
+                seq_printf(s, ",coherency=full");
+
         if (opts & OCFS2_MOUNT_NOUSERXATTR)
                 seq_printf(s, ",nouser_xattr");
         else