btrfs: advertise which crc32c implementation is being used at module load

Commit Message

David Sterba May 31, 2016, 11:57 p.m. UTC

From: Jeff Mahoney <[e-mail]>

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 <[e-mail]>
[ added a helper and used in module load-time message ]
Signed-off-by: David Sterba <[e-mail]>
---

Slightly modified version of Jeff's patch.

 fs/btrfs/hash.c  | 5 +++++
 fs/btrfs/hash.h  | 1 +
 fs/btrfs/super.c | 5 +++--
 3 files changed, 9 insertions(+), 2 deletions(-)

Patch

diff --git a/fs/btrfs/hash.c b/fs/btrfs/hash.c
index aae520b2aee5..a97fdc156a03 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 118a2316e5d3..c3a2ec554361 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 4e59a91a11e0..4397a303fc6c 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)