f2fs crypto: remove alloc_page for bounce_page

We don't need to call alloc_page() prior to mempool_alloc(), since the
mempool_alloc() calls alloc_page() internally.
And, if __GFP_WAIT is set, it never fails on page allocation, so let's
give GFP_NOWAIT and handle ENOMEM by writepage().
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/crypto.c

@@ -83,10 +83,7 @@ void f2fs_release_crypto_ctx(struct f2fs_crypto_ctx *ctx)
 	unsigned long flags;
 
 	if (ctx->flags & F2FS_WRITE_PATH_FL && ctx->w.bounce_page) {
-		if (ctx->flags & F2FS_BOUNCE_PAGE_REQUIRES_FREE_ENCRYPT_FL)
-			__free_page(ctx->w.bounce_page);
-		else
-			mempool_free(ctx->w.bounce_page, f2fs_bounce_page_pool);
+		mempool_free(ctx->w.bounce_page, f2fs_bounce_page_pool);
 		ctx->w.bounce_page = NULL;
 	}
 	ctx->w.control_page = NULL;
@@ -408,34 +405,28 @@ struct page *f2fs_encrypt(struct inode *inode,
 		return (struct page *)ctx;
 
 	/* The encryption operation will require a bounce page. */
-	ciphertext_page = alloc_page(GFP_NOFS);
+	ciphertext_page = mempool_alloc(f2fs_bounce_page_pool, GFP_NOWAIT);
 	if (!ciphertext_page) {
-		/*
-		 * This is a potential bottleneck, but at least we'll have
-		 * forward progress.
-		 */
-		ciphertext_page = mempool_alloc(f2fs_bounce_page_pool,
-							GFP_NOFS);
-		if (WARN_ON_ONCE(!ciphertext_page))
-			ciphertext_page = mempool_alloc(f2fs_bounce_page_pool,
-						GFP_NOFS | __GFP_WAIT);
-		ctx->flags &= ~F2FS_BOUNCE_PAGE_REQUIRES_FREE_ENCRYPT_FL;
-	} else {
-		ctx->flags |= F2FS_BOUNCE_PAGE_REQUIRES_FREE_ENCRYPT_FL;
+		err = -ENOMEM;
+		goto err_out;
 	}
+
 	ctx->flags |= F2FS_WRITE_PATH_FL;
 	ctx->w.bounce_page = ciphertext_page;
 	ctx->w.control_page = plaintext_page;
 	err = f2fs_page_crypto(ctx, inode, F2FS_ENCRYPT, plaintext_page->index,
 					plaintext_page, ciphertext_page);
-	if (err) {
-		f2fs_release_crypto_ctx(ctx);
-		return ERR_PTR(err);
-	}
+	if (err)
+		goto err_out;
+
 	SetPagePrivate(ciphertext_page);
 	set_page_private(ciphertext_page, (unsigned long)ctx);
 	lock_page(ciphertext_page);
 	return ciphertext_page;
+
+err_out:
+	f2fs_release_crypto_ctx(ctx);
+	return ERR_PTR(err);
 }
 
 /**

fs/f2fs/f2fs_crypto.h

@@ -84,8 +84,7 @@ struct f2fs_crypt_info {
 };
 
 #define F2FS_CTX_REQUIRES_FREE_ENCRYPT_FL             0x00000001
-#define F2FS_BOUNCE_PAGE_REQUIRES_FREE_ENCRYPT_FL     0x00000002
-#define F2FS_WRITE_PATH_FL			      0x00000004
+#define F2FS_WRITE_PATH_FL			      0x00000002
 
 struct f2fs_crypto_ctx {
 	union {