jbd2: switch to using the crc32c library

Now that the crc32c() library function directly takes advantage of
architecture-specific optimizations, it is unnecessary to go through the
crypto API. Just use crc32c(). This is much simpler, and it improves
performance due to eliminating the crypto API overhead.

Reviewed-by: Ard Biesheuvel <[e-mail]>
Reviewed-by: Darrick J. Wong <[e-mail]>
Acked-by: Theodore Ts'o <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Eric Biggers <[e-mail]>

fs/jbd2/Kconfig

···
 config JBD2
 	tristate
 	select CRC32
-	select CRYPTO
-	select CRYPTO_CRC32C
 	help
 	  This is a generic journaling layer for block devices that support
 	  both 32-bit and 64-bit block numbers.  It is currently used by

fs/jbd2/journal.c

···
 		return err;
 	}
 
-	/* Load the checksum driver */
 	if (jbd2_journal_has_csum_v2or3_feature(journal)) {
 		if (sb->s_checksum_type != JBD2_CRC32C_CHKSUM) {
 			printk(KERN_ERR "JBD2: Unknown checksum type\n");
 			return err;
 		}
 
-		journal->j_chksum_driver = crypto_alloc_shash("crc32c", 0, 0);
-		if (IS_ERR(journal->j_chksum_driver)) {
-			printk(KERN_ERR "JBD2: Cannot load crc32c driver.\n");
-			err = PTR_ERR(journal->j_chksum_driver);
-			journal->j_chksum_driver = NULL;
-			return err;
-		}
 		/* Check superblock checksum */
 		if (sb->s_checksum != jbd2_superblock_csum(journal, sb)) {
 			printk(KERN_ERR "JBD2: journal checksum error\n");
···
 
 err_cleanup:
 	percpu_counter_destroy(&journal->j_checkpoint_jh_count);
-	if (journal->j_chksum_driver)
-		crypto_free_shash(journal->j_chksum_driver);
 	kfree(journal->j_wbuf);
 	jbd2_journal_destroy_revoke(journal);
 	journal_fail_superblock(journal);
···
 	iput(journal->j_inode);
 	if (journal->j_revoke)
 		jbd2_journal_destroy_revoke(journal);
-	if (journal->j_chksum_driver)
-		crypto_free_shash(journal->j_chksum_driver);
 	kfree(journal->j_fc_wbuf);
 	kfree(journal->j_wbuf);
 	kfree(journal);
···
 		}
 	}
 
-	/* Load the checksum driver if necessary */
-	if ((journal->j_chksum_driver == NULL) &&
-	    INCOMPAT_FEATURE_ON(JBD2_FEATURE_INCOMPAT_CSUM_V3)) {
-		journal->j_chksum_driver = crypto_alloc_shash("crc32c", 0, 0);
-		if (IS_ERR(journal->j_chksum_driver)) {
-			printk(KERN_ERR "JBD2: Cannot load crc32c driver.\n");
-			journal->j_chksum_driver = NULL;
-			return 0;
-		}
-		/* Precompute checksum seed for all metadata */
-		journal->j_csum_seed = jbd2_chksum(journal, ~0, sb->s_uuid,
-						   sizeof(sb->s_uuid));
-	}
-
 	lock_buffer(journal->j_sb_buffer);
 
-	/* If enabling v3 checksums, update superblock */
+	/* If enabling v3 checksums, update superblock and precompute seed */
 	if (INCOMPAT_FEATURE_ON(JBD2_FEATURE_INCOMPAT_CSUM_V3)) {
 		sb->s_checksum_type = JBD2_CRC32C_CHKSUM;
 		sb->s_feature_compat &=
 			~cpu_to_be32(JBD2_FEATURE_COMPAT_CHECKSUM);
+		journal->j_csum_seed = jbd2_chksum(journal, ~0, sb->s_uuid,
+						   sizeof(sb->s_uuid));
 	}
 
 	/* If enabling v1 checksums, downgrade superblock */

include/linux/jbd2.h

···
 #include <linux/slab.h>
 #include <linux/bit_spinlock.h>
 #include <linux/blkdev.h>
-#include <crypto/hash.h>
+#include <linux/crc32c.h>
 #endif
 
 #define journal_oom_retry 1
···
 	void *j_private;
 
 	/**
-	 * @j_chksum_driver:
-	 *
-	 * Reference to checksum algorithm driver via cryptoapi.
-	 */
-	struct crypto_shash *j_chksum_driver;
-
-	/**
 	 * @j_csum_seed:
 	 *
 	 * Precomputed journal UUID checksum for seeding other checksums.
···
 
 static inline int jbd2_journal_has_csum_v2or3(journal_t *journal)
 {
-	WARN_ON_ONCE(jbd2_journal_has_csum_v2or3_feature(journal) &&
-		     journal->j_chksum_driver == NULL);
-
-	return journal->j_chksum_driver != NULL;
+	return jbd2_journal_has_csum_v2or3_feature(journal);
 }
 
 static inline int jbd2_journal_get_num_fc_blks(journal_superblock_t *jsb)
···
 #define BJ_Reserved	4	/* Buffer is reserved for access by journal */
 #define BJ_Types	5
 
-/* JBD uses a CRC32 checksum */
-#define JBD_MAX_CHECKSUM_SIZE 4
-
 static inline u32 jbd2_chksum(journal_t *journal, u32 crc,
 			      const void *address, unsigned int length)
 {
-	DEFINE_RAW_FLEX(struct shash_desc, desc, __ctx,
-		DIV_ROUND_UP(JBD_MAX_CHECKSUM_SIZE,
-			     sizeof(*((struct shash_desc *)0)->__ctx)));
-	int err;
-
-	BUG_ON(crypto_shash_descsize(journal->j_chksum_driver) >
-		JBD_MAX_CHECKSUM_SIZE);
-
-	desc->tfm = journal->j_chksum_driver;
-	*(u32 *)desc->__ctx = crc;
-
-	err = crypto_shash_update(desc, address, length);
-	BUG_ON(err);
-
-	return *(u32 *)desc->__ctx;
+	return crc32c(crc, address, length);
 }
 
 /* Return most recent uncommitted transaction */