ext2: Deprecate DAX

Since PMEM didn't quite lift off, DAX isn't as widely used as we
originally hoped. Thus it doesn't seem warranted to support
implementation of DAX in ext2 driver when the same filesystem can be
accessed through ext4 driver as a "simple implementation". Just
deprecate DAX support in ext2 targetting completely dropping the code at
the end of 2025.

Link: https://lore.kernel.org/all/uiu7rcmtooxgbscaiiim7czqsca52bgrt6aiszsafq7jj4n3e7@ge6mfzcmnorl
Signed-off-by: Jan Kara <[email protected]>

Author: jankara

fs/ext2/super.c

@@ -601,7 +601,8 @@ static int ext2_parse_param(struct fs_context *fc, struct fs_parameter *param)
 	case Opt_dax:
 #ifdef CONFIG_FS_DAX
 		ext2_msg_fc(fc, KERN_WARNING,
-		    "DAX enabled. Warning: EXPERIMENTAL, use at your own risk");
+		    "DAX enabled. Warning: DAX support in ext2 driver is deprecated"
+		    " and will be removed at the end of 2025. Please use ext4 driver instead.");
 		ctx_set_mount_opt(ctx, EXT2_MOUNT_DAX);
 #else
 		ext2_msg_fc(fc, KERN_INFO, "dax option not supported");