btrfs: fix fast csum implementation detection

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>

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 883a3671a9774b298bf05619789d9bc0282752be..5b1b5e1a63c8f4a41c85bbf7821d51ffd62bc336 100644 (file)
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -2347,6 +2347,20 @@ 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 fa03a4b2d90496a6e11aeeb151a868e8fc3b4c1d..e43b16199e22b0a7289bf3ed56627d9a03405b6d 100644 (file)
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -1824,8 +1824,6 @@ 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)