[PATCH v2 15/18] ext4: switch to using the crc32c library

[Eric Biggers]

From: Eric Biggers <ebiggers at google.com>

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 <ardb at kernel.org>
Signed-off-by: Eric Biggers <ebiggers at google.com>
---
 fs/ext4/Kconfig |  3 +--
 fs/ext4/ext4.h  | 25 +++----------------------
 fs/ext4/super.c | 15 ---------------
 3 files changed, 4 insertions(+), 39 deletions(-)

diff --git a/fs/ext4/Kconfig b/fs/ext4/Kconfig
index e20d59221fc0..c9ca41d91a6c 100644
--- a/fs/ext4/Kconfig
+++ b/fs/ext4/Kconfig
@@ -29,12 +29,11 @@ config EXT3_FS_SECURITY
 config EXT4_FS
 	tristate "The Extended 4 (ext4) filesystem"
 	select BUFFER_HEAD
 	select JBD2
 	select CRC16
-	select CRYPTO
-	select CRYPTO_CRC32C
+	select CRC32
 	select FS_IOMAP
 	select FS_ENCRYPTION_ALGS if FS_ENCRYPTION
 	help
 	  This is the next generation of the ext3 filesystem.
 
diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 44b0d418143c..99aa512a7de1 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -31,11 +31,11 @@
 #include <linux/wait.h>
 #include <linux/sched/signal.h>
 #include <linux/blockgroup_lock.h>
 #include <linux/percpu_counter.h>
 #include <linux/ratelimit.h>
-#include <crypto/hash.h>
+#include <linux/crc32c.h>
 #include <linux/falloc.h>
 #include <linux/percpu-rwsem.h>
 #include <linux/fiemap.h>
 #ifdef __KERNEL__
 #include <linux/compat.h>
@@ -1660,13 +1660,10 @@ struct ext4_sb_info {
 	struct task_struct *s_mmp_tsk;
 
 	/* record the last minlen when FITRIM is called. */
 	unsigned long s_last_trim_minblks;
 
-	/* Reference to checksum algorithm driver via cryptoapi */
-	struct crypto_shash *s_chksum_driver;
-
 	/* Precomputed FS UUID checksum for seeding other checksums */
 	__u32 s_csum_seed;
 
 	/* Reclaim extents from extent status tree */
 	struct shrinker *s_es_shrinker;
@@ -2465,23 +2462,11 @@ static inline __le16 ext4_rec_len_to_disk(unsigned len, unsigned blocksize)
 #define DX_HASH_LAST 			DX_HASH_SIPHASH
 
 static inline u32 ext4_chksum(struct ext4_sb_info *sbi, u32 crc,
 			      const void *address, unsigned int length)
 {
-	struct {
-		struct shash_desc shash;
-		char ctx[4];
-	} desc;
-
-	BUG_ON(crypto_shash_descsize(sbi->s_chksum_driver)!=sizeof(desc.ctx));
-
-	desc.shash.tfm = sbi->s_chksum_driver;
-	*(u32 *)desc.ctx = crc;
-
-	BUG_ON(crypto_shash_update(&desc.shash, address, length));
-
-	return *(u32 *)desc.ctx;
+	return crc32c(crc, address, length);
 }
 
 #ifdef __KERNEL__
 
 /* hash info structure used by the directory hash */
@@ -3278,15 +3263,11 @@ extern void ext4_group_desc_csum_set(struct super_block *sb, __u32 group,
 extern int ext4_register_li_request(struct super_block *sb,
 				    ext4_group_t first_not_zeroed);
 
 static inline int ext4_has_metadata_csum(struct super_block *sb)
 {
-	WARN_ON_ONCE(ext4_has_feature_metadata_csum(sb) &&
-		     !EXT4_SB(sb)->s_chksum_driver);
-
-	return ext4_has_feature_metadata_csum(sb) &&
-	       (EXT4_SB(sb)->s_chksum_driver != NULL);
+	return ext4_has_feature_metadata_csum(sb);
 }
 
 static inline int ext4_has_group_desc_csum(struct super_block *sb)
 {
 	return ext4_has_feature_gdt_csum(sb) || ext4_has_metadata_csum(sb);
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 16a4ce704460..1a821093cc0d 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -1371,12 +1371,10 @@ static void ext4_put_super(struct super_block *sb)
 	 * Now that we are completely done shutting down the
 	 * superblock, we need to actually destroy the kobject.
 	 */
 	kobject_put(&sbi->s_kobj);
 	wait_for_completion(&sbi->s_kobj_unregister);
-	if (sbi->s_chksum_driver)
-		crypto_free_shash(sbi->s_chksum_driver);
 	kfree(sbi->s_blockgroup_lock);
 	fs_put_dax(sbi->s_daxdev, NULL);
 	fscrypt_free_dummy_policy(&sbi->s_dummy_enc_policy);
 #if IS_ENABLED(CONFIG_UNICODE)
 	utf8_unload(sb->s_encoding);
@@ -4586,19 +4584,10 @@ static int ext4_init_metadata_csum(struct super_block *sb, struct ext4_super_blo
 		return -EINVAL;
 	}
 	ext4_setup_csum_trigger(sb, EXT4_JTR_ORPHAN_FILE,
 				ext4_orphan_file_block_trigger);
 
-	/* Load the checksum driver */
-	sbi->s_chksum_driver = crypto_alloc_shash("crc32c", 0, 0);
-	if (IS_ERR(sbi->s_chksum_driver)) {
-		int ret = PTR_ERR(sbi->s_chksum_driver);
-		ext4_msg(sb, KERN_ERR, "Cannot load crc32c driver.");
-		sbi->s_chksum_driver = NULL;
-		return ret;
-	}
-
 	/* Check superblock checksum */
 	if (!ext4_superblock_csum_verify(sb, es)) {
 		ext4_msg(sb, KERN_ERR, "VFS: Found ext4 filesystem with "
 			 "invalid superblock checksum.  Run e2fsck?");
 		return -EFSBADCRC;
@@ -5638,13 +5627,10 @@ failed_mount8: __maybe_unused
 	flush_work(&sbi->s_sb_upd_work);
 	ext4_stop_mmpd(sbi);
 	del_timer_sync(&sbi->s_err_report);
 	ext4_group_desc_free(sbi);
 failed_mount:
-	if (sbi->s_chksum_driver)
-		crypto_free_shash(sbi->s_chksum_driver);
-
 #if IS_ENABLED(CONFIG_UNICODE)
 	utf8_unload(sb->s_encoding);
 #endif
 
 #ifdef CONFIG_QUOTA
@@ -7433,8 +7419,7 @@ static void __exit ext4_exit_fs(void)
 }
 
 MODULE_AUTHOR("Remy Card, Stephen Tweedie, Andrew Morton, Andreas Dilger, Theodore Ts'o and others");
 MODULE_DESCRIPTION("Fourth Extended Filesystem");
 MODULE_LICENSE("GPL");
-MODULE_SOFTDEP("pre: crc32c");
 module_init(ext4_init_fs)
 module_exit(ext4_exit_fs)
-- 
2.47.0