bcachefs: Add an option to disable reflink support

Reflink might be buggy, so we're adding an option so users can help
bisect what's going on.
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/bcachefs_format.h

@@ -1266,6 +1266,8 @@ LE64_BITMASK(BCH_SB_PRJQUOTA,		struct bch_sb, flags[0], 59, 60);
 
 LE64_BITMASK(BCH_SB_HAS_ERRORS,		struct bch_sb, flags[0], 60, 61);
 
+LE64_BITMASK(BCH_SB_REFLINK,		struct bch_sb, flags[0], 61, 62);
+
 /* 61-64 unused */
 
 LE64_BITMASK(BCH_SB_STR_HASH_TYPE,	struct bch_sb, flags[1],  0,  4);

fs/bcachefs/fs-io.c

@@ -2812,6 +2812,9 @@ loff_t bch2_remap_file_range(struct file *file_src, loff_t pos_src,
 	u64 aligned_len;
 	loff_t ret = 0;
 
+	if (!c->opts.reflink)
+		return -EOPNOTSUPP;
+
 	if (remap_flags & ~(REMAP_FILE_DEDUP|REMAP_FILE_ADVISORY))
 		return -EINVAL;
 

fs/bcachefs/opts.h

@@ -207,6 +207,11 @@ enum opt_type {
 	  OPT_BOOL(),							\
 	  BCH_SB_PRJQUOTA,		false,				\
 	  NULL,		"Enable project quotas")			\
+	x(reflink,			u8,				\
+	  OPT_FORMAT|OPT_MOUNT|OPT_RUNTIME,				\
+	  OPT_BOOL(),							\
+	  BCH_SB_REFLINK,		true,				\
+	  NULL,		"Enable reflink support")			\
 	x(degraded,			u8,				\
 	  OPT_MOUNT,							\
 	  OPT_BOOL(),							\

fs/bcachefs/reflink.c

@@ -167,6 +167,9 @@ s64 bch2_remap_range(struct bch_fs *c,
 	u64 src_done, dst_done;
 	int ret = 0, ret2 = 0;
 
+	if (!c->opts.reflink)
+		return -EOPNOTSUPP;
+
 	if (!percpu_ref_tryget(&c->writes))
 		return -EROFS;