From: Christoph Hellwig <hch@lst.de>
Date: Wed, 29 Mar 2023 09:13:05 +0900
Subject: [PATCH] btrfs: fix fast csum implementation detection
References: bsc#1012628
Patch-mainline: 6.2.12
Git-commit: 68d99ab0e9221ef54506f827576c5a914680eeaf

commit 68d99ab0e9221ef54506f827576c5a914680eeaf upstream.

The BTRFS_FS_CSUM_IMPL_FAST flag is currently set whenever a non-generic
crc32c is detected, which is the incorrect check if the file system uses
a different checksumming algorithm.  Refactor the code to only check
this if crc32c is actually used.  Note that in an ideal world the
information if an algorithm is hardware accelerated or not should be
provided by the crypto API instead, but that's left for another day.

CC: stable@vger.kernel.org # 5.4.x: c8a5f8ca9a9c: btrfs: print checksum type and implementation at mount time
CC: stable@vger.kernel.org # 5.4.x
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
 fs/btrfs/disk-io.c | 14 ++++++++++++++
 fs/btrfs/super.c   |  2 --
 2 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index fde40112..174d196d 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -2433,6 +2433,20 @@ static int btrfs_init_csum_hash(struct btrfs_fs_info *fs_info, u16 csum_type)
 
 	fs_info->csum_shash = csum_shash;
 
+	/*
+	 * Check if the checksum implementation is a fast accelerated one.
+	 * As-is this is a bit of a hack and should be replaced once the csum
+	 * implementations provide that information themselves.
+	 */
+	switch (csum_type) {
+	case BTRFS_CSUM_TYPE_CRC32:
+		if (!strstr(crypto_shash_driver_name(csum_shash), "generic"))
+			set_bit(BTRFS_FS_CSUM_IMPL_FAST, &fs_info->flags);
+		break;
+	default:
+		break;
+	}
+
 	btrfs_info(fs_info, "using %s (%s) checksum algorithm",
 			btrfs_super_csum_name(csum_type),
 			crypto_shash_driver_name(csum_shash));
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 8dd8f56b..3f3c8f91 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -1515,8 +1515,6 @@ static struct dentry *btrfs_mount_root(struct file_system_type *fs_type,
 		shrinker_debugfs_rename(&s->s_shrink, "sb-%s:%s", fs_type->name,
 					s->s_id);
 		btrfs_sb(s)->bdev_holder = fs_type;
-		if (!strstr(crc32c_impl(), "generic"))
-			set_bit(BTRFS_FS_CSUM_IMPL_FAST, &fs_info->flags);
 		error = btrfs_fill_super(s, fs_devices, data);
 	}
 	if (!error)
-- 
2.35.3