bcachefs: Don't BUG_ON() when superblock feature wasn't set for compressed data

We don't allocate the mempools for compression/decompression unless we
need them - but that means there's an inconsistency to check for.

Reported-by: syzbot+cb3fbcfb417448cfd278@syzkaller.appspotmail.com
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/compress.c

@@ -2,7 +2,9 @@
 #include "bcachefs.h"
 #include "checksum.h"
 #include "compress.h"
+#include "error.h"
 #include "extents.h"
+#include "opts.h"
 #include "super-io.h"
 
 #include <linux/lz4.h>
@@ -178,7 +180,16 @@ static int __bio_uncompress(struct bch_fs *c, struct bio *src,
 
 	enum bch_compression_opts opt = bch2_compression_type_to_opt(crc.compression_type);
 	mempool_t *workspace_pool = &c->compress_workspace[opt];
-	BUG_ON(!mempool_initialized(workspace_pool));
+	if (unlikely(!mempool_initialized(workspace_pool))) {
+		if (fsck_err(c, compression_type_not_marked_in_sb,
+			     "compression type %s set but not marked in superblock",
+			     __bch2_compression_types[crc.compression_type]))
+			ret = bch2_check_set_has_compressed_data(c, opt);
+		else
+			ret = -BCH_ERR_compression_workspace_not_initialized;
+		if (ret)
+			goto out;
+	}
 
 	src_data = bio_map_or_bounce(c, src, READ);
 
@@ -234,6 +245,7 @@ static int __bio_uncompress(struct bch_fs *c, struct bio *src,
 		BUG();
 	}
 	ret = 0;
+fsck_err:
 out:
 	bio_unmap_or_unbounce(c, src_data);
 	return ret;
@@ -420,7 +432,17 @@ static unsigned __bio_compress(struct bch_fs *c,
 	BUG_ON(compression.type >= BCH_COMPRESSION_OPT_NR);
 
 	mempool_t *workspace_pool = &c->compress_workspace[compression.type];
-	BUG_ON(!mempool_initialized(workspace_pool));
+	if (unlikely(!mempool_initialized(workspace_pool))) {
+		if (fsck_err(c, compression_opt_not_marked_in_sb,
+			     "compression opt %s set but not marked in superblock",
+			     bch2_compression_opts[compression.type])) {
+			ret = bch2_check_set_has_compressed_data(c, compression.type);
+			if (ret) /* memory allocation failure, don't compress */
+				return 0;
+		} else {
+			return 0;
+		}
+	}
 
 	/* If it's only one block, don't bother trying to compress: */
 	if (src->bi_iter.bi_size <= c->opts.block_size)
@@ -502,6 +524,9 @@ static unsigned __bio_compress(struct bch_fs *c,
 err:
 	ret = BCH_COMPRESSION_TYPE_incompressible;
 	goto out;
+fsck_err:
+	ret = 0;
+	goto out;
 }
 
 unsigned bch2_bio_compress(struct bch_fs *c,

fs/bcachefs/errcode.h

@@ -54,6 +54,7 @@
 	x(ENOMEM,			ENOMEM_compression_bounce_read_init)	\
 	x(ENOMEM,			ENOMEM_compression_bounce_write_init)	\
 	x(ENOMEM,			ENOMEM_compression_workspace_init)	\
+	x(EIO,				compression_workspace_not_initialized)	\
 	x(ENOMEM,			ENOMEM_bucket_gens)			\
 	x(ENOMEM,			ENOMEM_buckets_nouse)			\
 	x(ENOMEM,			ENOMEM_usage_init)			\

fs/bcachefs/opts.c

@@ -54,7 +54,7 @@ const char * const __bch2_csum_opts[] = {
 	NULL
 };
 
-static const char * const __bch2_compression_types[] = {
+const char * const __bch2_compression_types[] = {
 	BCH_COMPRESSION_TYPES()
 	NULL
 };

fs/bcachefs/opts.h

@@ -17,6 +17,7 @@ extern const char * const bch2_sb_features[];
 extern const char * const bch2_sb_compat[];
 extern const char * const __bch2_btree_ids[];
 extern const char * const __bch2_csum_opts[];
+extern const char * const __bch2_compression_types[];
 extern const char * const bch2_compression_opts[];
 extern const char * const __bch2_str_hash_types[];
 extern const char * const bch2_str_hash_opts[];

fs/bcachefs/sb-errors_format.h

@@ -305,7 +305,9 @@ enum bch_fsck_flags {
 	x(accounting_key_replicas_devs_unsorted,		280,	FSCK_AUTOFIX)	\
 	x(accounting_key_version_0,				282,	FSCK_AUTOFIX)	\
 	x(logged_op_but_clean,					283,	FSCK_AUTOFIX)	\
-	x(MAX,							295,	0)
+	x(compression_opt_not_marked_in_sb,			295,	FSCK_AUTOFIX)	\
+	x(compression_type_not_marked_in_sb,			296,	FSCK_AUTOFIX)	\
+	x(MAX,							297,	0)
 
 enum bch_sb_error_id {
 #define x(t, n, ...) BCH_FSCK_ERR_##t = n,