ext2, ext4: warn when mounting with dax enabled

Orabug: 22913653

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>
(cherry picked from commit ef83b6e8f40bb24b92ad73b5889732346e54a793)
Signed-off-by: Dan Duval <dan.duval@oracle.com>

diff --git a/fs/ext2/super.c b/fs/ext2/super.c
index 68e85b664d4a5883671a4b007a261e66d61cc9d4..b3146dbe69bc732fd5b17eef0a93cdd38f3b7bb9 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 0d284635ef3cdcfc12fbaad7072393976a8a3555..6d594dc5249ee97a14b0cde6306fe2071496220d 100644 (file)
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -1643,8 +1643,12 @@ 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