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 3a71cea684208f16beb587f61989bfffb0a0d006..748d35afc90266123407d61d7aed944f2e9ad9ca 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 753f4e68b820da0dd78fc7a7e3a66e529846ea0b..c9ab67da6e5abbe871ce4bc7760c007e07f2b479 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