fscrypt: Delay bounce page pool allocation until needed

Since fscrypt users can now indicated if fscrypt_encrypt_page() should
use a bounce page, we can delay the bounce page pool initialization util
it is really needed. That is until fscrypt_operations has no
FS_CFLG_OWN_PAGES flag set.
Signed-off-by: NDavid Gstir <david@sigma-star.at>
Signed-off-by: NTheodore Ts'o <tytso@mit.edu>

fs/crypto/crypto.c

@@ -525,17 +525,22 @@ static void fscrypt_destroy(void)
 
 /**
  * fscrypt_initialize() - allocate major buffers for fs encryption.
+ * @cop_flags:  fscrypt operations flags
  *
  * We only call this when we start accessing encrypted files, since it
  * results in memory getting allocated that wouldn't otherwise be used.
  *
  * Return: Zero on success, non-zero otherwise.
  */
-int fscrypt_initialize(void)
+int fscrypt_initialize(unsigned int cop_flags)
 {
 	int i, res = -ENOMEM;
 
-	if (fscrypt_bounce_page_pool)
+	/*
+	 * No need to allocate a bounce page pool if there already is one or
+	 * this FS won't use it.
+	 */
+	if (cop_flags & FS_CFLG_OWN_PAGES || fscrypt_bounce_page_pool)
 		return 0;
 
 	mutex_lock(&fscrypt_init_mutex);

fs/crypto/fscrypt_private.h

@@ -85,7 +85,7 @@ struct fscrypt_completion_result {
 
 
 /* crypto.c */
-int fscrypt_initialize(void);
+int fscrypt_initialize(unsigned int cop_flags);
 
 /* keyinfo.c */
 extern int fscrypt_get_crypt_info(struct inode *);

fs/crypto/keyinfo.c

@@ -188,7 +188,7 @@ int fscrypt_get_crypt_info(struct inode *inode)
 	u8 *raw_key = NULL;
 	int res;
 
-	res = fscrypt_initialize();
+	res = fscrypt_initialize(inode->i_sb->s_cop->flags);
 	if (res)
 		return res;
 

include/linux/fscrypto.h

@@ -168,7 +168,6 @@ static inline void fscrypt_set_d_op(struct dentry *dentry)
 #if IS_ENABLED(CONFIG_FS_ENCRYPTION)
 /* crypto.c */
 extern struct kmem_cache *fscrypt_info_cachep;
-
 extern struct fscrypt_ctx *fscrypt_get_ctx(const struct inode *, gfp_t);
 extern void fscrypt_release_ctx(struct fscrypt_ctx *);
 extern struct page *fscrypt_encrypt_page(const struct inode *, struct page *,