bcachefs: bcachefs_metadata_version_casefolding

This patch implements support for case-insensitive file name lookups
in bcachefs.

The implementation uses the same UTF-8 lowering and normalization that
ext4 and f2fs is using.

More information is provided in Documentation/bcachefs/casefolding.rst

Compatibility notes:

This uses the new versioning scheme for incompatible features where an
incompatible feature is tied to a version number: the superblock says
"we may use incompat features up to x" and "incompat features up to x
are in use", disallowing mounting by previous versions.

Additionally, and old style incompat feature bit is used, so that
kernels without utf8 casefolding support know if casefolding
specifically is in use and they're allowed to mount.

Signed-off-by: Joshua Ashton <joshua@froggi.es>
Cc: André Almeida <andrealmeid@igalia.com>
Cc: Gabriel Krisman Bertazi <krisman@suse.de>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

1 files changed, 25 insertions, 0 deletions

diff --git a/fs/bcachefs/fs-ioctl.c b/fs/bcachefs/fs-ioctl.c
index 15725b4ce393..4465a2a821e3 100644
--- a/fs/bcachefs/fs-ioctl.c
+++ b/fs/bcachefs/fs-ioctl.c
@@ -54,6 +54,31 @@ static int bch2_inode_flags_set(struct btree_trans *trans,
 	    (newflags & (BCH_INODE_nodump|BCH_INODE_noatime)) != newflags)
 		return -EINVAL;
 
+	if ((newflags ^ oldflags) & BCH_INODE_casefolded) {
+#ifdef CONFIG_UNICODE
+		int ret = 0;
+		/* Not supported on individual files. */
+		if (!S_ISDIR(bi->bi_mode))
+			return -EOPNOTSUPP;
+
+		/*
+		 * Make sure the dir is empty, as otherwise we'd need to
+		 * rehash everything and update the dirent keys.
+		 */
+		ret = bch2_empty_dir_trans(trans, inode_inum(inode));
+		if (ret < 0)
+			return ret;
+
+		if (!bch2_request_incompat_feature(c,bcachefs_metadata_version_casefolding))
+			return -EOPNOTSUPP;
+
+		bch2_check_set_feature(c, BCH_FEATURE_casefolding);
+#else
+		printk(KERN_ERR "Cannot use casefolding on a kernel without CONFIG_UNICODE\n");
+		return -EOPNOTSUPP;
+#endif
+	}
+
 	if (s->set_projinherit) {
 		bi->bi_fields_set &= ~(1 << Inode_opt_project);
 		bi->bi_fields_set |= ((int) s->projinherit << Inode_opt_project);