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 fde40112a25930895397d4e90f8c7f2487e01db3..174d196d69609a24f2183e329a0bcd3fcdebc527 100644 (file)
--- 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 8dd8f56bf7824f5cf28a39702eb4246f64eee5c0..3f3c8f9186f90b2183558f66ca2c520a042698b2 100644 (file)
--- 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)