f2fs crypto: use per-inode tfm structure

This patch applies the following ext4 patch:

  ext4 crypto: use per-inode tfm structure

As suggested by Herbert Xu, we shouldn't allocate a new tfm each time
we read or write a page.  Instead we can use a single tfm hanging off
the inode's crypt_info structure for all of our encryption needs for
that inode, since the tfm can be used by multiple crypto requests in
parallel.

Also use cmpxchg() to avoid races that could result in crypt_info
structure getting doubly allocated or doubly freed.

Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

1 files changed, 6 insertions, 76 deletions

diff --git a/fs/f2fs/crypto.c b/fs/f2fs/crypto.c
index c6d11229aee4..2c7819aebcc5 100644
--- a/fs/f2fs/crypto.c
+++ b/fs/f2fs/crypto.c
@@ -91,8 +91,6 @@ void f2fs_release_crypto_ctx(struct f2fs_crypto_ctx *ctx)
 	}
 	ctx->w.control_page = NULL;
 	if (ctx->flags & F2FS_CTX_REQUIRES_FREE_ENCRYPT_FL) {
-		if (ctx->tfm)
-			crypto_free_tfm(ctx->tfm);
 		kmem_cache_free(f2fs_crypto_ctx_cachep, ctx);
 	} else {
 		spin_lock_irqsave(&f2fs_crypto_ctx_lock, flags);
@@ -113,7 +111,6 @@ void f2fs_release_crypto_ctx(struct f2fs_crypto_ctx *ctx)
 struct f2fs_crypto_ctx *f2fs_get_crypto_ctx(struct inode *inode)
 {
 	struct f2fs_crypto_ctx *ctx = NULL;
-	int res = 0;
 	unsigned long flags;
 	struct f2fs_crypt_info *ci = F2FS_I(inode)->i_crypt_info;
 
@@ -138,56 +135,13 @@ struct f2fs_crypto_ctx *f2fs_get_crypto_ctx(struct inode *inode)
 	spin_unlock_irqrestore(&f2fs_crypto_ctx_lock, flags);
 	if (!ctx) {
 		ctx = kmem_cache_zalloc(f2fs_crypto_ctx_cachep, GFP_NOFS);
-		if (!ctx) {
-			res = -ENOMEM;
-			goto out;
-		}
+		if (!ctx)
+			return ERR_PTR(-ENOMEM);
 		ctx->flags |= F2FS_CTX_REQUIRES_FREE_ENCRYPT_FL;
 	} else {
 		ctx->flags &= ~F2FS_CTX_REQUIRES_FREE_ENCRYPT_FL;
 	}
 	ctx->flags &= ~F2FS_WRITE_PATH_FL;
-
-	/*
-	 * Allocate a new Crypto API context if we don't already have
-	 * one or if it isn't the right mode.
-	 */
-	if (ctx->tfm && (ctx->mode != ci->ci_data_mode)) {
-		crypto_free_tfm(ctx->tfm);
-		ctx->tfm = NULL;
-		ctx->mode = F2FS_ENCRYPTION_MODE_INVALID;
-	}
-	if (!ctx->tfm) {
-		switch (ci->ci_data_mode) {
-		case F2FS_ENCRYPTION_MODE_AES_256_XTS:
-			ctx->tfm = crypto_ablkcipher_tfm(
-				crypto_alloc_ablkcipher("xts(aes)", 0, 0));
-			break;
-		case F2FS_ENCRYPTION_MODE_AES_256_GCM:
-			/*
-			 * TODO(mhalcrow): AEAD w/ gcm(aes);
-			 * crypto_aead_setauthsize()
-			 */
-			ctx->tfm = ERR_PTR(-ENOTSUPP);
-			break;
-		default:
-			BUG();
-		}
-		if (IS_ERR_OR_NULL(ctx->tfm)) {
-			res = PTR_ERR(ctx->tfm);
-			ctx->tfm = NULL;
-			goto out;
-		}
-		ctx->mode = ci->ci_data_mode;
-	}
-	BUG_ON(ci->ci_size != f2fs_encryption_key_size(ci->ci_data_mode));
-
-out:
-	if (res) {
-		if (!IS_ERR_OR_NULL(ctx))
-			f2fs_release_crypto_ctx(ctx);
-		ctx = ERR_PTR(res);
-	}
 	return ctx;
 }
 
@@ -229,11 +183,8 @@ static void f2fs_crypto_destroy(void)
 {
 	struct f2fs_crypto_ctx *pos, *n;
 
-	list_for_each_entry_safe(pos, n, &f2fs_free_crypto_ctxs, free_list) {
-		if (pos->tfm)
-			crypto_free_tfm(pos->tfm);
+	list_for_each_entry_safe(pos, n, &f2fs_free_crypto_ctxs, free_list)
 		kmem_cache_free(f2fs_crypto_ctx_cachep, pos);
-	}
 	INIT_LIST_HEAD(&f2fs_free_crypto_ctxs);
 	if (f2fs_bounce_page_pool)
 		mempool_destroy(f2fs_bounce_page_pool);
@@ -383,32 +334,11 @@ static int f2fs_page_crypto(struct f2fs_crypto_ctx *ctx,
 	struct ablkcipher_request *req = NULL;
 	DECLARE_F2FS_COMPLETION_RESULT(ecr);
 	struct scatterlist dst, src;
-	struct f2fs_inode_info *fi = F2FS_I(inode);
-	struct crypto_ablkcipher *atfm = __crypto_ablkcipher_cast(ctx->tfm);
+	struct f2fs_crypt_info *ci = F2FS_I(inode)->i_crypt_info;
+	struct crypto_ablkcipher *tfm = ci->ci_ctfm;
 	int res = 0;
 
-	BUG_ON(!ctx->tfm);
-	BUG_ON(ctx->mode != fi->i_crypt_info->ci_data_mode);
-
-	if (ctx->mode != F2FS_ENCRYPTION_MODE_AES_256_XTS) {
-		printk_ratelimited(KERN_ERR
-				"%s: unsupported crypto algorithm: %d\n",
-				__func__, ctx->mode);
-		return -ENOTSUPP;
-	}
-
-	crypto_ablkcipher_clear_flags(atfm, ~0);
-	crypto_tfm_set_flags(ctx->tfm, CRYPTO_TFM_REQ_WEAK_KEY);
-
-	res = crypto_ablkcipher_setkey(atfm, fi->i_crypt_info->ci_raw,
-					fi->i_crypt_info->ci_size);
-	if (res) {
-		printk_ratelimited(KERN_ERR
-				"%s: crypto_ablkcipher_setkey() failed\n",
-				__func__);
-		return res;
-	}
-	req = ablkcipher_request_alloc(atfm, GFP_NOFS);
+	req = ablkcipher_request_alloc(tfm, GFP_NOFS);
 	if (!req) {
 		printk_ratelimited(KERN_ERR
 				"%s: crypto_request_alloc() failed\n",