[v3,16/18] jbd2: switch to using the crc32c library

From: Eric Biggers <ebiggers@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@kernel.org>
Signed-off-by: Eric Biggers <ebiggers@google.com>
---
 fs/jbd2/Kconfig      |  2 --
 fs/jbd2/journal.c    | 25 ++-----------------------
 include/linux/jbd2.h | 31 +++----------------------------
 3 files changed, 5 insertions(+), 53 deletions(-)

On Sun, Nov 03, 2024 at 02:31:52PM -0800, Eric Biggers wrote:
> From: Eric Biggers <ebiggers@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@kernel.org>
> Signed-off-by: Eric Biggers <ebiggers@google.com>
> ---
>  fs/jbd2/Kconfig      |  2 --
>  fs/jbd2/journal.c    | 25 ++-----------------------
>  include/linux/jbd2.h | 31 +++----------------------------
>  3 files changed, 5 insertions(+), 53 deletions(-)
> 
> diff --git a/fs/jbd2/Kconfig b/fs/jbd2/Kconfig
> index 4ad2c67f93f1..9c19e1512101 100644
> --- a/fs/jbd2/Kconfig
> +++ b/fs/jbd2/Kconfig
> @@ -1,11 +1,9 @@
>  # SPDX-License-Identifier: GPL-2.0-only
>  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
>  	  the ext4 and OCFS2 filesystems, but it could also be used to add
>  	  journal support to other file systems or block devices such
> diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
> index 97f487c3d8fc..56cea5a738a7 100644
> --- a/fs/jbd2/journal.c
> +++ b/fs/jbd2/journal.c
> @@ -1373,24 +1373,16 @@ static int journal_check_superblock(journal_t *journal)
>  		printk(KERN_ERR "JBD2: Can't enable checksumming v1 and v2/3 "
>  		       "at the same time!\n");
>  		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 = -EFSBADCRC;
>  			return err;
> @@ -1611,12 +1603,10 @@ static journal_t *journal_init_common(struct block_device *bdev,
>  
>  	return journal;
>  
>  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);
>  	kfree(journal);
>  	return ERR_PTR(err);
> @@ -2194,12 +2184,10 @@ int jbd2_journal_destroy(journal_t *journal)
>  	if (journal->j_proc_entry)
>  		jbd2_stats_proc_exit(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);
>  
>  	return err;
> @@ -2340,23 +2328,14 @@ int jbd2_journal_set_features(journal_t *journal, unsigned long compat,
>  			pr_err("JBD2: Cannot enable fast commits.\n");
>  			return 0;
>  		}
>  	}
>  
> -	/* 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 */
> +	/* Precompute checksum seed for all metadata */
> +	if (INCOMPAT_FEATURE_ON(JBD2_FEATURE_INCOMPAT_CSUM_V3))
>  		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 (INCOMPAT_FEATURE_ON(JBD2_FEATURE_INCOMPAT_CSUM_V3)) {
> diff --git a/include/linux/jbd2.h b/include/linux/jbd2.h
> index 8aef9bb6ad57..33d25a3d15f1 100644
> --- a/include/linux/jbd2.h
> +++ b/include/linux/jbd2.h
> @@ -26,11 +26,11 @@
>  #include <linux/mutex.h>
>  #include <linux/timer.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
>  
>  /*
> @@ -1239,17 +1239,10 @@ struct journal_s
>  	 * An opaque pointer to fs-private information.  ext3 puts its
>  	 * superblock pointer here.
>  	 */
>  	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.
>  	 */
> @@ -1748,14 +1741,11 @@ static inline bool jbd2_journal_has_csum_v2or3_feature(journal_t *j)
>  	return jbd2_has_feature_csum2(j) || jbd2_has_feature_csum3(j);
>  }
>  
>  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);

Same comment as my last reply about removing trivial helpers, but
otherwise
Reviewed-by: Darrick J. Wong <djwong@kernel.org>

If you push this for 6.13 I'd be happy that the shash junk finally went
away.  The onstack struct desc thing in the _chksum() functions was by
far the most sketchy part of the ext4/jbd2 metadata csum project. :)

--D

>  }
>  
>  static inline int jbd2_journal_get_num_fc_blks(journal_superblock_t *jsb)
>  {
>  	int num_fc_blocks = be32_to_cpu(jsb->s_num_fc_blks);
> @@ -1794,26 +1784,11 @@ static inline unsigned long jbd2_log_space_left(journal_t *journal)
>  #define JBD_MAX_CHECKSUM_SIZE 4
>  
>  static inline u32 jbd2_chksum(journal_t *journal, u32 crc,
>  			      const void *address, unsigned int length)
>  {
> -	struct {
> -		struct shash_desc shash;
> -		char ctx[JBD_MAX_CHECKSUM_SIZE];
> -	} desc;
> -	int err;
> -
> -	BUG_ON(crypto_shash_descsize(journal->j_chksum_driver) >
> -		JBD_MAX_CHECKSUM_SIZE);
> -
> -	desc.shash.tfm = journal->j_chksum_driver;
> -	*(u32 *)desc.ctx = crc;
> -
> -	err = crypto_shash_update(&desc.shash, address, length);
> -	BUG_ON(err);
> -
> -	return *(u32 *)desc.ctx;
> +	return crc32c(crc, address, length);
>  }
>  
>  /* Return most recent uncommitted transaction */
>  static inline tid_t  jbd2_get_latest_transaction(journal_t *journal)
>  {
> -- 
> 2.47.0
> 
>

On Sun, Nov 03, 2024 at 02:31:52PM -0800, Eric Biggers wrote:
> From: Eric Biggers <ebiggers@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@kernel.org>
> Signed-off-by: Eric Biggers <ebiggers@google.com>

Acked-by: Theodore Ts'o <tytso@mit.edu>

On Mon, Nov 04, 2024 at 08:01:36AM -0800, Darrick J. Wong wrote:
> Same comment as my last reply about removing trivial helpers, but
> otherwise
> Reviewed-by: Darrick J. Wong <djwong@kernel.org>
> 
> If you push this for 6.13 I'd be happy that the shash junk finally went
> away.  The onstack struct desc thing in the _chksum() functions was by
> far the most sketchy part of the ext4/jbd2 metadata csum project. :)

It will take a bit longer I'm afraid, since this patchset depends on patches
that are currently enqueued in three different trees for 6.13.  My current plan
is to target 6.14, and get this series into into linux-next shortly after the
6.13 merge window closes.

- Eric