ext2, ext4: warn when mounting with dax enabled

commit ef83b6e8f40bb24b92ad73b5889732346e54a793 upstream.

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: "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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/ext2/super.c b/fs/ext2/super.c
index 900e19cf9ef6fbb4057e95f2cc1f81c44ccd3377..2597b0663bf25a27ab44738c2cbbe9604043eacb 100644 (file)
--- a/fs/ext2/super.c
+++ b/fs/ext2/super.c
@@ -566,6 +566,8 @@ 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 df84bd256c9f5b2965c16e748189cc2a9f50f6f0..7683892d855c00690865fd0baadaf8ad7bbb53b6 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