ext4: load the crc32c driver if necessary

Obtain a reference to the cryptoapi and crc32c if we mount a
filesystem with metadata checksumming enabled.

Signed-off-by: Darrick J. Wong <djwong@us.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

3 files changed, 41 insertions, 0 deletions

diff --git a/fs/ext4/Kconfig b/fs/ext4/Kconfig
index 9ed1bb1f319f..c22f17021b6e 100644
--- a/fs/ext4/Kconfig
+++ b/fs/ext4/Kconfig
@@ -2,6 +2,8 @@ config EXT4_FS
         tristate "The Extended 4 (ext4) filesystem"
         select JBD2
         select CRC16
+        select CRYPTO
+        select CRYPTO_CRC32C
         help
           This is the next generation of the ext3 filesystem.
 
diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 61dd739b64f0..f19192bde094 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -29,6 +29,7 @@
 #include <linux/wait.h>
 #include <linux/blockgroup_lock.h>
 #include <linux/percpu_counter.h>
+#include <crypto/hash.h>
 #ifdef __KERNEL__
 #include <linux/compat.h>
 #endif
@@ -1276,6 +1277,9 @@ struct ext4_sb_info {
 
         /* record the last minlen when FITRIM is called. */
         atomic_t s_last_trim_minblks;
+
+        /* Reference to checksum algorithm driver via cryptoapi */
+        struct crypto_shash *s_chksum_driver;
 };
 
 static inline struct ext4_sb_info *EXT4_SB(struct super_block *sb)
@@ -1639,6 +1643,25 @@ static inline __le16 ext4_rec_len_to_disk(unsigned len, unsigned blocksize)
 #define DX_HASH_HALF_MD4_UNSIGNED       4
 #define DX_HASH_TEA_UNSIGNED            5
 
+static inline u32 ext4_chksum(struct ext4_sb_info *sbi, u32 crc,
+                              const void *address, unsigned int length)
+{
+        struct {
+                struct shash_desc shash;
+                char ctx[crypto_shash_descsize(sbi->s_chksum_driver)];
+        } desc;
+        int err;
+
+        desc.shash.tfm = sbi->s_chksum_driver;
+        desc.shash.flags = 0;
+        *(u32 *)desc.ctx = crc;
+
+        err = crypto_shash_update(&desc.shash, address, length);
+        BUG_ON(err);
+
+        return *(u32 *)desc.ctx;
+}
+
 #ifdef __KERNEL__
 
 /* hash info structure used by the directory hash */
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index f489ffb3605d..11a0a7078da7 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -915,6 +915,8 @@ static void ext4_put_super(struct super_block *sb)
         unlock_super(sb);
         kobject_put(&sbi->s_kobj);
         wait_for_completion(&sbi->s_kobj_unregister);
+        if (sbi->s_chksum_driver)
+                crypto_free_shash(sbi->s_chksum_driver);
         kfree(sbi->s_blockgroup_lock);
         kfree(sbi);
 }
@@ -3043,6 +3045,18 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
                 goto cantfind_ext4;
         }
 
+        /* Load the checksum driver */
+        if (EXT4_HAS_RO_COMPAT_FEATURE(sb,
+                                       EXT4_FEATURE_RO_COMPAT_METADATA_CSUM)) {
+                sbi->s_chksum_driver = crypto_alloc_shash("crc32c", 0, 0);
+                if (IS_ERR(sbi->s_chksum_driver)) {
+                        ext4_msg(sb, KERN_ERR, "Cannot load crc32c driver.");
+                        ret = PTR_ERR(sbi->s_chksum_driver);
+                        sbi->s_chksum_driver = NULL;
+                        goto failed_mount;
+                }
+        }
+
         /* Set defaults before we parse the mount options */
         def_mount_opts = le32_to_cpu(es->s_default_mount_opts);
         set_opt(sb, INIT_INODE_TABLE);
@@ -3728,6 +3742,8 @@ failed_mount2:
                 brelse(sbi->s_group_desc[i]);
         ext4_kvfree(sbi->s_group_desc);
 failed_mount:
+        if (sbi->s_chksum_driver)
+                crypto_free_shash(sbi->s_chksum_driver);
         if (sbi->s_proc) {
                 remove_proc_entry("options", sbi->s_proc);
                 remove_proc_entry(sb->s_id, ext4_proc_root);