ext2, ext4: warn when mounting with dax enabled

Similar to XFS warn when mounting DAX while it is still considered under
development.  Also, aspects of the DAX implementation, for example
synchronization against multiple faults and faults causing block
allocation, depend on the correct implementation in the filesystem.  The
maturity of a given DAX implementation is filesystem specific.

Cc: <stable@vger.kernel.org>
Cc: "Theodore Ts'o" <tytso@mit.edu>
Cc: Matthew Wilcox <willy@linux.intel.com>
Cc: linux-ext4@vger.kernel.org
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reported-by: Dave Chinner <david@fromorbit.com>
Acked-by: Jan Kara <jack@suse.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

diff --git a/fs/ext2/super.c b/fs/ext2/super.c
index 3a71cea..748d35a 100644 (file)
--- a/fs/ext2/super.c
+++ b/fs/ext2/super.c
@@ -569,6 +569,8 @@ static int parse_options(char *options, struct super_block *sb)
                        /* Fall through */
                case Opt_dax:
 #ifdef CONFIG_FS_DAX
+                       ext2_msg(sb, KERN_WARNING,
+               "DAX enabled. Warning: EXPERIMENTAL, use at your own risk");
                        set_opt(sbi->s_mount_opt, DAX);
 #else
                        ext2_msg(sb, KERN_INFO, "dax option not supported");

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 753f4e6..c9ab67d 100644 (file)
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -1664,8 +1664,12 @@ static int handle_mount_opt(struct super_block *sb, char *opt, int token,
                }
                sbi->s_jquota_fmt = m->mount_opt;
 #endif
-#ifndef CONFIG_FS_DAX
        } else if (token == Opt_dax) {
+#ifdef CONFIG_FS_DAX
+               ext4_msg(sb, KERN_WARNING,
+               "DAX enabled. Warning: EXPERIMENTAL, use at your own risk");
+                       sbi->s_mount_opt |= m->mount_opt;
+#else
                ext4_msg(sb, KERN_INFO, "dax option not supported");
                return -1;
 #endif