fscrypt: optimize fscrypt_initialize()

fscrypt_initialize() is a "one-time init" function that is called
whenever the key is set up for any inode on any filesystem.  Make it
implement "one-time init" more efficiently by not taking a global mutex
in the "already initialized case" and doing fewer pointer dereferences.

Link: https://lore.kernel.org/r/20230406181245.36091-1-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>

diff --git a/fs/crypto/crypto.c b/fs/crypto/crypto.c
index bf642479269a542b97157177b5c1bbf80e7665da..6a837e4b80dcb3a052508d7e64bca409956236d1 100644 (file)
--- a/fs/crypto/crypto.c
+++ b/fs/crypto/crypto.c
@@ -308,19 +308,24 @@ EXPORT_SYMBOL(fscrypt_decrypt_block_inplace);
 
 /**
  * fscrypt_initialize() - allocate major buffers for fs encryption.
- * @cop_flags:  fscrypt operations flags
+ * @sb: the filesystem superblock
  *
  * We only call this when we start accessing encrypted files, since it
  * results in memory getting allocated that wouldn't otherwise be used.
  *
  * Return: 0 on success; -errno on failure
  */
-int fscrypt_initialize(unsigned int cop_flags)
+int fscrypt_initialize(struct super_block *sb)
 {
        int err = 0;
+       mempool_t *pool;
+
+       /* pairs with smp_store_release() below */
+       if (likely(smp_load_acquire(&fscrypt_bounce_page_pool)))
+               return 0;
 
        /* No need to allocate a bounce page pool if this FS won't use it. */
-       if (cop_flags & FS_CFLG_OWN_PAGES)
+       if (sb->s_cop->flags & FS_CFLG_OWN_PAGES)
                return 0;
 
        mutex_lock(&fscrypt_init_mutex);
@@ -328,11 +333,11 @@ int fscrypt_initialize(unsigned int cop_flags)
                goto out_unlock;
 
        err = -ENOMEM;
-       fscrypt_bounce_page_pool =
-               mempool_create_page_pool(num_prealloc_crypto_pages, 0);
-       if (!fscrypt_bounce_page_pool)
+       pool = mempool_create_page_pool(num_prealloc_crypto_pages, 0);
+       if (!pool)
                goto out_unlock;
-
+       /* pairs with smp_load_acquire() above */
+       smp_store_release(&fscrypt_bounce_page_pool, pool);
        err = 0;
 out_unlock:
        mutex_unlock(&fscrypt_init_mutex);

diff --git a/fs/crypto/fscrypt_private.h b/fs/crypto/fscrypt_private.h
index 05310aa741fd686f65792abce3b7ad68ab5efa2d..7ab5a7b7eef8c3dd366c3ef24742f01cd5018205 100644 (file)
--- a/fs/crypto/fscrypt_private.h
+++ b/fs/crypto/fscrypt_private.h
@@ -264,7 +264,7 @@ typedef enum {
 
 /* crypto.c */
 extern struct kmem_cache *fscrypt_info_cachep;
-int fscrypt_initialize(unsigned int cop_flags);
+int fscrypt_initialize(struct super_block *sb);
 int fscrypt_crypt_block(const struct inode *inode, fscrypt_direction_t rw,
                        u64 lblk_num, struct page *src_page,
                        struct page *dest_page, unsigned int len,

diff --git a/fs/crypto/keysetup.c b/fs/crypto/keysetup.c
index 84cdae30632809f33a8613ea8fb1c2b671840fde..361f41ef46c787d8a317e536e0bf72fe638294dc 100644 (file)
--- a/fs/crypto/keysetup.c
+++ b/fs/crypto/keysetup.c
@@ -560,7 +560,7 @@ fscrypt_setup_encryption_info(struct inode *inode,
        struct fscrypt_master_key *mk = NULL;
        int res;
 
-       res = fscrypt_initialize(inode->i_sb->s_cop->flags);
+       res = fscrypt_initialize(inode->i_sb);
        if (res)
                return res;