From 5f9e1059d9347191b271bf7d13bd83db57594d2a Mon Sep 17 00:00:00 2001
From: Jeff Mahoney <jeffm@suse.com>
Date: Wed, 16 Sep 2015 15:34:53 +0200
Subject: btrfs: advertise which crc32c implementation is being used at module
 load

Since several architectures support hardware-accelerated crc32c
calculation, it would be nice to confirm that btrfs is actually using it.

We can see an elevated use count for the module, but it doesn't actually
show who the users are.  This patch simply prints the name of the driver
after successfully initializing the shash.

Signed-off-by: Jeff Mahoney <jeffm@suse.com>
[ added a helper and used in module load-time message ]
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/hash.c b/fs/btrfs/hash.c
index aae520b..a97fdc1 100644
--- a/fs/btrfs/hash.c
+++ b/fs/btrfs/hash.c
@@ -24,6 +24,11 @@ int __init btrfs_hash_init(void)
 	return PTR_ERR_OR_ZERO(tfm);
 }
 
+const char* btrfs_crc32c_impl(void)
+{
+	return crypto_tfm_alg_driver_name(crypto_shash_tfm(tfm));
+}
+
 void btrfs_hash_exit(void)
 {
 	crypto_free_shash(tfm);
diff --git a/fs/btrfs/hash.h b/fs/btrfs/hash.h
index 118a231..c3a2ec5 100644
--- a/fs/btrfs/hash.h
+++ b/fs/btrfs/hash.h
@@ -22,6 +22,7 @@
 int __init btrfs_hash_init(void);
 
 void btrfs_hash_exit(void);
+const char* btrfs_crc32c_impl(void);
 
 u32 btrfs_crc32c(u32 crc, const void *address, unsigned int length);
 
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 4e59a91..4397a30 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -2303,7 +2303,7 @@ static void btrfs_interface_exit(void)
 
 static void btrfs_print_mod_info(void)
 {
-	printk(KERN_INFO "Btrfs loaded"
+	printk(KERN_INFO "Btrfs loaded, crc32c=%s"
 #ifdef CONFIG_BTRFS_DEBUG
 			", debug=on"
 #endif
@@ -2313,7 +2313,8 @@ static void btrfs_print_mod_info(void)
 #ifdef CONFIG_BTRFS_FS_CHECK_INTEGRITY
 			", integrity-checker=on"
 #endif
-			"\n");
+			"\n",
+			btrfs_crc32c_impl());
 }
 
 static int btrfs_run_sanity_tests(void)
-- 
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