erofs: simplify compression configuration parser

commit efb4fb02ce upstream.

Move erofs_load_compr_cfgs() into decompressor.c as well as introduce
a callback instead of a hard-coded switch for each algorithm for
simplicity.

Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Link: https://lore.kernel.org/r/20231022130957.11398-1-xiang@kernel.org
Stable-dep-of: 118a8cf504 ("erofs: fix inconsistent per-file compression format")
Signed-off-by: Yue Hu <huyue2@coolpad.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

fs/erofs/compress.h

@@ -21,6 +21,8 @@ struct z_erofs_decompress_req {
 };
 
 struct z_erofs_decompressor {
+	int (*config)(struct super_block *sb, struct erofs_super_block *dsb,
+		      void *data, int size);
 	int (*decompress)(struct z_erofs_decompress_req *rq,
 			  struct page **pagepool);
 	char *name;
@@ -93,6 +95,8 @@ int z_erofs_decompress(struct z_erofs_decompress_req *rq,
 		       struct page **pagepool);
 
 /* prototypes for specific algorithms */
+int z_erofs_load_lzma_config(struct super_block *sb,
+			struct erofs_super_block *dsb, void *data, int size);
 int z_erofs_lzma_decompress(struct z_erofs_decompress_req *rq,
 			    struct page **pagepool);
 #endif

fs/erofs/decompressor.c

@@ -24,11 +24,11 @@ struct z_erofs_lz4_decompress_ctx {
 	unsigned int oend;
 };
 
-int z_erofs_load_lz4_config(struct super_block *sb,
+static int z_erofs_load_lz4_config(struct super_block *sb,
-			    struct erofs_super_block *dsb,
+			    struct erofs_super_block *dsb, void *data, int size)
-			    struct z_erofs_lz4_cfgs *lz4, int size)
 {
 	struct erofs_sb_info *sbi = EROFS_SB(sb);
+	struct z_erofs_lz4_cfgs *lz4 = data;
 	u16 distance;
 
 	if (lz4) {
@@ -374,17 +374,71 @@ static struct z_erofs_decompressor decompressors[] = {
 		.name = "interlaced"
 	},
 	[Z_EROFS_COMPRESSION_LZ4] = {
+		.config = z_erofs_load_lz4_config,
 		.decompress = z_erofs_lz4_decompress,
 		.name = "lz4"
 	},
 #ifdef CONFIG_EROFS_FS_ZIP_LZMA
 	[Z_EROFS_COMPRESSION_LZMA] = {
+		.config = z_erofs_load_lzma_config,
 		.decompress = z_erofs_lzma_decompress,
 		.name = "lzma"
 	},
 #endif
 };
 
+int z_erofs_parse_cfgs(struct super_block *sb, struct erofs_super_block *dsb)
+{
+	struct erofs_sb_info *sbi = EROFS_SB(sb);
+	struct erofs_buf buf = __EROFS_BUF_INITIALIZER;
+	unsigned int algs, alg;
+	erofs_off_t offset;
+	int size, ret = 0;
+
+	if (!erofs_sb_has_compr_cfgs(sbi)) {
+		sbi->available_compr_algs = Z_EROFS_COMPRESSION_LZ4;
+		return z_erofs_load_lz4_config(sb, dsb, NULL, 0);
+	}
+
+	sbi->available_compr_algs = le16_to_cpu(dsb->u1.available_compr_algs);
+	if (sbi->available_compr_algs & ~Z_EROFS_ALL_COMPR_ALGS) {
+		erofs_err(sb, "unidentified algorithms %x, please upgrade kernel",
+			  sbi->available_compr_algs & ~Z_EROFS_ALL_COMPR_ALGS);
+		return -EOPNOTSUPP;
+	}
+
+	offset = EROFS_SUPER_OFFSET + sbi->sb_size;
+	alg = 0;
+	for (algs = sbi->available_compr_algs; algs; algs >>= 1, ++alg) {
+		void *data;
+
+		if (!(algs & 1))
+			continue;
+
+		data = erofs_read_metadata(sb, &buf, &offset, &size);
+		if (IS_ERR(data)) {
+			ret = PTR_ERR(data);
+			break;
+		}
+
+		if (alg >= ARRAY_SIZE(decompressors) ||
+		    !decompressors[alg].config) {
+			erofs_err(sb, "algorithm %d isn't enabled on this kernel",
+				  alg);
+			ret = -EOPNOTSUPP;
+		} else {
+			ret = decompressors[alg].config(sb,
+					dsb, data, size);
+		}
+
+		kfree(data);
+		if (ret)
+			break;
+	}
+	erofs_put_metabuf(&buf);
+	return ret;
+}
+
 int z_erofs_decompress(struct z_erofs_decompress_req *rq,
 		       struct page **pagepool)
 {

fs/erofs/decompressor_lzma.c

@@ -72,10 +72,10 @@ int z_erofs_lzma_init(void)
 }
 
 int z_erofs_load_lzma_config(struct super_block *sb,
-			     struct erofs_super_block *dsb,
+			struct erofs_super_block *dsb, void *data, int size)
-			     struct z_erofs_lzma_cfgs *lzma, int size)
 {
 	static DEFINE_MUTEX(lzma_resize_mutex);
+	struct z_erofs_lzma_cfgs *lzma = data;
 	unsigned int dict_size, i;
 	struct z_erofs_lzma *strm, *head = NULL;
 	int err;

fs/erofs/internal.h

@@ -471,6 +471,8 @@ struct erofs_map_dev {
 
 /* data.c */
 extern const struct file_operations erofs_file_fops;
+void *erofs_read_metadata(struct super_block *sb, struct erofs_buf *buf,
+			  erofs_off_t *offset, int *lengthp);
 void erofs_unmap_metabuf(struct erofs_buf *buf);
 void erofs_put_metabuf(struct erofs_buf *buf);
 void *erofs_bread(struct erofs_buf *buf, struct inode *inode,
@@ -565,9 +567,7 @@ void z_erofs_exit_zip_subsystem(void);
 int erofs_try_to_free_all_cached_pages(struct erofs_sb_info *sbi,
 				       struct erofs_workgroup *egrp);
 int erofs_try_to_free_cached_page(struct page *page);
-int z_erofs_load_lz4_config(struct super_block *sb,
+int z_erofs_parse_cfgs(struct super_block *sb, struct erofs_super_block *dsb);
-			    struct erofs_super_block *dsb,
-			    struct z_erofs_lz4_cfgs *lz4, int len);
 #else
 static inline void erofs_shrinker_register(struct super_block *sb) {}
 static inline void erofs_shrinker_unregister(struct super_block *sb) {}
@@ -575,36 +575,14 @@ static inline int erofs_init_shrinker(void) { return 0; }
 static inline void erofs_exit_shrinker(void) {}
 static inline int z_erofs_init_zip_subsystem(void) { return 0; }
 static inline void z_erofs_exit_zip_subsystem(void) {}
-static inline int z_erofs_load_lz4_config(struct super_block *sb,
-				  struct erofs_super_block *dsb,
-				  struct z_erofs_lz4_cfgs *lz4, int len)
-{
-	if (lz4 || dsb->u1.lz4_max_distance) {
-		erofs_err(sb, "lz4 algorithm isn't enabled");
-		return -EINVAL;
-	}
-	return 0;
-}
 #endif	/* !CONFIG_EROFS_FS_ZIP */
 
 #ifdef CONFIG_EROFS_FS_ZIP_LZMA
 int z_erofs_lzma_init(void);
 void z_erofs_lzma_exit(void);
-int z_erofs_load_lzma_config(struct super_block *sb,
-			     struct erofs_super_block *dsb,
-			     struct z_erofs_lzma_cfgs *lzma, int size);
 #else
 static inline int z_erofs_lzma_init(void) { return 0; }
 static inline int z_erofs_lzma_exit(void) { return 0; }
-static inline int z_erofs_load_lzma_config(struct super_block *sb,
-			     struct erofs_super_block *dsb,
-			     struct z_erofs_lzma_cfgs *lzma, int size) {
-	if (lzma) {
-		erofs_err(sb, "lzma algorithm isn't enabled");
-		return -EINVAL;
-	}
-	return 0;
-}
 #endif	/* !CONFIG_EROFS_FS_ZIP */
 
 /* flags for erofs_fscache_register_cookie() */

fs/erofs/super.c

@@ -126,8 +126,8 @@ static bool check_layout_compatibility(struct super_block *sb,
 
 #ifdef CONFIG_EROFS_FS_ZIP
 /* read variable-sized metadata, offset will be aligned by 4-byte */
-static void *erofs_read_metadata(struct super_block *sb, struct erofs_buf *buf,
+void *erofs_read_metadata(struct super_block *sb, struct erofs_buf *buf,
-				 erofs_off_t *offset, int *lengthp)
+			  erofs_off_t *offset, int *lengthp)
 {
 	u8 *buffer, *ptr;
 	int len, i, cnt;
@@ -159,64 +159,15 @@ static void *erofs_read_metadata(struct super_block *sb, struct erofs_buf *buf,
 	}
 	return buffer;
 }
-
-static int erofs_load_compr_cfgs(struct super_block *sb,
-				 struct erofs_super_block *dsb)
-{
-	struct erofs_sb_info *sbi = EROFS_SB(sb);
-	struct erofs_buf buf = __EROFS_BUF_INITIALIZER;
-	unsigned int algs, alg;
-	erofs_off_t offset;
-	int size, ret = 0;
-
-	sbi->available_compr_algs = le16_to_cpu(dsb->u1.available_compr_algs);
-	if (sbi->available_compr_algs & ~Z_EROFS_ALL_COMPR_ALGS) {
-		erofs_err(sb, "try to load compressed fs with unsupported algorithms %x",
-			  sbi->available_compr_algs & ~Z_EROFS_ALL_COMPR_ALGS);
-		return -EINVAL;
-	}
-
-	offset = EROFS_SUPER_OFFSET + sbi->sb_size;
-	alg = 0;
-	for (algs = sbi->available_compr_algs; algs; algs >>= 1, ++alg) {
-		void *data;
-
-		if (!(algs & 1))
-			continue;
-
-		data = erofs_read_metadata(sb, &buf, &offset, &size);
-		if (IS_ERR(data)) {
-			ret = PTR_ERR(data);
-			break;
-		}
-
-		switch (alg) {
-		case Z_EROFS_COMPRESSION_LZ4:
-			ret = z_erofs_load_lz4_config(sb, dsb, data, size);
-			break;
-		case Z_EROFS_COMPRESSION_LZMA:
-			ret = z_erofs_load_lzma_config(sb, dsb, data, size);
-			break;
-		default:
-			DBG_BUGON(1);
-			ret = -EFAULT;
-		}
-		kfree(data);
-		if (ret)
-			break;
-	}
-	erofs_put_metabuf(&buf);
-	return ret;
-}
 #else
-static int erofs_load_compr_cfgs(struct super_block *sb,
+static int z_erofs_parse_cfgs(struct super_block *sb,
-				 struct erofs_super_block *dsb)
+			      struct erofs_super_block *dsb)
 {
-	if (dsb->u1.available_compr_algs) {
+	if (!dsb->u1.available_compr_algs)
-		erofs_err(sb, "try to load compressed fs when compression is disabled");
+		return 0;
-		return -EINVAL;
+
-	}
+	erofs_err(sb, "compression disabled, unable to mount compressed EROFS");
-	return 0;
+	return -EOPNOTSUPP;
 }
 #endif
 
@@ -398,10 +349,7 @@ static int erofs_read_superblock(struct super_block *sb)
 	}
 
 	/* parse on-disk compression configurations */
-	if (erofs_sb_has_compr_cfgs(sbi))
+	ret = z_erofs_parse_cfgs(sb, dsb);
-		ret = erofs_load_compr_cfgs(sb, dsb);
-	else
-		ret = z_erofs_load_lz4_config(sb, dsb, NULL, 0);
 	if (ret < 0)
 		goto out;