f2fs: compress: support chksum

This patch supports to store chksum value with compressed
data, and verify the integrality of compressed data while
reading the data.

The feature can be enabled through specifying mount option
'compress_chksum'.

Signed-off-by: Chao Yu <[e-mail]>
Signed-off-by: Jaegeuk Kim <[e-mail]>

Documentation/filesystems/f2fs.rst

···
 			 For other files, we can still enable compression via ioctl.
 			 Note that, there is one reserved special extension '*', it
 			 can be set to enable compression for all files.
+compress_chksum		 Support verifying chksum of raw data in compressed cluster.
 inlinecrypt		 When possible, encrypt/decrypt the contents of encrypted
 			 files using the blk-crypto framework rather than
 			 filesystem-layer encryption. This allows the use of

fs/f2fs/compress.c

···
 				f2fs_cops[fi->i_compress_algorithm];
 	unsigned int max_len, new_nr_cpages;
 	struct page **new_cpages;
+	u32 chksum = 0;
 	int i, ret;
 
 	trace_f2fs_compress_pages_start(cc->inode, cc->cluster_idx,
···
 	}
 
 	cc->cbuf->clen = cpu_to_le32(cc->clen);
+
+	if (fi->i_compress_flag & 1 << COMPRESS_CHKSUM)
+		chksum = f2fs_crc32(F2FS_I_SB(cc->inode),
+					cc->cbuf->cdata, cc->clen);
+	cc->cbuf->chksum = cpu_to_le32(chksum);
 
 	for (i = 0; i < COMPRESS_DATA_RESERVED_SIZE; i++)
 		cc->cbuf->reserved[i] = cpu_to_le32(0);
···
 	}
 
 	ret = cops->decompress_pages(dic);
+
+	if (!ret && fi->i_compress_flag & 1 << COMPRESS_CHKSUM) {
+		u32 provided = le32_to_cpu(dic->cbuf->chksum);
+		u32 calculated = f2fs_crc32(sbi, dic->cbuf->cdata, dic->clen);
+
+		if (provided != calculated) {
+			if (!is_inode_flag_set(dic->inode, FI_COMPRESS_CORRUPT)) {
+				set_inode_flag(dic->inode, FI_COMPRESS_CORRUPT);
+				printk_ratelimited(
+					"%sF2FS-fs (%s): checksum invalid, nid = %lu, %x vs %x",
+					KERN_INFO, sbi->sb->s_id, dic->inode->i_ino,
+					provided, calculated);
+			}
+			set_sbi_flag(sbi, SBI_NEED_FSCK);
+			WARN_ON_ONCE(1);
+		}
+	}
 
 out_vunmap_cbuf:
 	vm_unmap_ram(dic->cbuf, dic->nr_cpages);

fs/f2fs/f2fs.h

···
 
 	/* For compression */
 	unsigned char compress_algorithm;	/* algorithm type */
-	unsigned compress_log_size;		/* cluster log size */
+	unsigned char compress_log_size;	/* cluster log size */
+	bool compress_chksum;			/* compressed data chksum */
 	unsigned char compress_ext_cnt;		/* extension count */
 	unsigned char extensions[COMPRESS_EXT_NUM][F2FS_EXTENSION_LEN];	/* extensions */
 };
···
 	FI_ATOMIC_REVOKE_REQUEST, /* request to drop atomic data */
 	FI_VERITY_IN_PROGRESS,	/* building fs-verity Merkle tree */
 	FI_COMPRESSED_FILE,	/* indicate file's data can be compressed */
+	FI_COMPRESS_CORRUPT,	/* indicate compressed cluster is corrupted */
 	FI_MMAP_FILE,		/* indicate file was mmapped */
 	FI_MAX,			/* max flag, never be used */
 };
···
 	atomic_t i_compr_blocks;		/* # of compressed blocks */
 	unsigned char i_compress_algorithm;	/* algorithm type */
 	unsigned char i_log_cluster_size;	/* log of cluster size */
+	unsigned short i_compress_flag;		/* compress flag */
 	unsigned int i_cluster_size;		/* cluster size */
 };
 
···
 	COMPRESS_MAX,
 };
 
-#define COMPRESS_DATA_RESERVED_SIZE		5
+enum compress_flag {
+	COMPRESS_CHKSUM,
+	COMPRESS_MAX_FLAG,
+};
+
+#define COMPRESS_DATA_RESERVED_SIZE		4
 struct compress_data {
 	__le32 clen;			/* compressed data size */
+	__le32 chksum;			/* compressed data chksum */
 	__le32 reserved[COMPRESS_DATA_RESERVED_SIZE];	/* reserved */
 	u8 cdata[];			/* compressed data */
 };
···
 			F2FS_OPTION(sbi).compress_algorithm;
 	F2FS_I(inode)->i_log_cluster_size =
 			F2FS_OPTION(sbi).compress_log_size;
+	F2FS_I(inode)->i_compress_flag =
+			F2FS_OPTION(sbi).compress_chksum ?
+				1 << COMPRESS_CHKSUM : 0;
 	F2FS_I(inode)->i_cluster_size =
 			1 << F2FS_I(inode)->i_log_cluster_size;
 	F2FS_I(inode)->i_flags |= F2FS_COMPR_FL;

fs/f2fs/inode.c

···
 					le64_to_cpu(ri->i_compr_blocks));
 			fi->i_compress_algorithm = ri->i_compress_algorithm;
 			fi->i_log_cluster_size = ri->i_log_cluster_size;
+			fi->i_compress_flag = le16_to_cpu(ri->i_compress_flag);
 			fi->i_cluster_size = 1 << fi->i_log_cluster_size;
 			set_inode_flag(inode, FI_COMPRESSED_FILE);
 		}
···
 					&F2FS_I(inode)->i_compr_blocks));
 			ri->i_compress_algorithm =
 				F2FS_I(inode)->i_compress_algorithm;
+			ri->i_compress_flag =
+				cpu_to_le16(F2FS_I(inode)->i_compress_flag);
 			ri->i_log_cluster_size =
 				F2FS_I(inode)->i_log_cluster_size;
 		}

fs/f2fs/super.c

···
 	Opt_compress_algorithm,
 	Opt_compress_log_size,
 	Opt_compress_extension,
+	Opt_compress_chksum,
 	Opt_atgc,
 	Opt_err,
 };
···
 	{Opt_compress_algorithm, "compress_algorithm=%s"},
 	{Opt_compress_log_size, "compress_log_size=%u"},
 	{Opt_compress_extension, "compress_extension=%s"},
+	{Opt_compress_chksum, "compress_chksum"},
 	{Opt_atgc, "atgc"},
 	{Opt_err, NULL},
 };
···
 			F2FS_OPTION(sbi).compress_ext_cnt++;
 			kfree(name);
 			break;
+		case Opt_compress_chksum:
+			F2FS_OPTION(sbi).compress_chksum = true;
+			break;
 #else
 		case Opt_compress_algorithm:
 		case Opt_compress_log_size:
 		case Opt_compress_extension:
+		case Opt_compress_chksum:
 			f2fs_info(sbi, "compression options not supported");
 			break;
 #endif
···
 		seq_printf(seq, ",compress_extension=%s",
 			F2FS_OPTION(sbi).extensions[i]);
 	}
+
+	if (F2FS_OPTION(sbi).compress_chksum)
+		seq_puts(seq, ",compress_chksum");
 }
 
 static int f2fs_show_options(struct seq_file *seq, struct dentry *root)

include/linux/f2fs_fs.h

···
 			__le64 i_compr_blocks;	/* # of compressed blocks */
 			__u8 i_compress_algorithm;	/* compress algorithm */
 			__u8 i_log_cluster_size;	/* log of cluster size */
-			__le16 i_padding;		/* padding */
+			__le16 i_compress_flag;		/* compress flag */
 			__le32 i_extra_end[0];	/* for attribute size calculation */
 		} __packed;
 		__le32 i_addr[DEF_ADDRS_PER_INODE];	/* Pointers to data blocks */