From: Eric Biggers <ebiggers@xxxxxxxxxx>
Document all fields of struct fscrypt_operations so that it's more clear
what filesystems that use (or plan to use) fs/crypto/ need to implement.
Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx>
---
include/linux/fscrypt.h | 109 ++++++++++++++++++++++++++++++++++++++--
1 file changed, 105 insertions(+), 4 deletions(-)
diff --git a/include/linux/fscrypt.h b/include/linux/fscrypt.h
index b7bfd0cd4f3e..e912ed9141d9 100644
--- a/include/linux/fscrypt.h
+++ b/include/linux/fscrypt.h
@@ -47,27 +47,128 @@ struct fscrypt_name {
#define FSCRYPT_SET_CONTEXT_MAX_SIZE 40
#ifdef CONFIG_FS_ENCRYPTION
+
/*
- * fscrypt superblock flags
+ * If set, the fscrypt bounce page pool won't be allocated (unless another
+ * filesystem needs it). Set this if the filesystem always uses its own bounce
+ * pages for writes and therefore won't need the fscrypt bounce page pool.
*/
#define FS_CFLG_OWN_PAGES (1U << 1)
-/*
- * crypto operations for filesystems
- */
+/* Crypto operations for filesystems */
struct fscrypt_operations {
+
+ /* Set of optional flags; see above for allowed flags */
unsigned int flags;
+
+ /*
+ * If set, this is a filesystem-specific key description prefix that
+ * will be accepted for "logon" keys for v1 fscrypt policies, in
+ * addition to the generic prefix "fscrypt:". This functionality is
+ * deprecated, so new filesystems shouldn't set this field.
+ */
const char *key_prefix;
+
+ /*
+ * Get the fscrypt context of the given inode.
+ *
+ * @inode: the inode whose context to get
+ * @ctx: the buffer into which to get the context
+ * @len: length of the @ctx buffer in bytes
+ *
+ * Return: On success, returns the length of the context in bytes; this
+ * may be less than @len. On failure, returns -ENODATA if the
+ * inode doesn't have a context, -ERANGE if the context is
+ * longer than @len, or another -errno code.
+ */
int (*get_context)(struct inode *inode, void *ctx, size_t len);
+
+ /*
+ * Set an fscrypt context on the given inode.
+ *
+ * @inode: the inode whose context to set. The inode won't already have
+ * an fscrypt context.
+ * @ctx: the context to set
+ * @len: length of @ctx in bytes (at most FSCRYPT_SET_CONTEXT_MAX_SIZE)
+ * @fs_data: If called from fscrypt_set_context(), this will be the
+ * value the filesystem passed to fscrypt_set_context().
+ * Otherwise (i.e. when called from
+ * FS_IOC_SET_ENCRYPTION_POLICY) this will be NULL.
+ *
+ * i_rwsem will be held for write.
+ *
+ * Return: 0 on success, -errno on failure.
+ */
int (*set_context)(struct inode *inode, const void *ctx, size_t len,
void *fs_data);
+
+ /*
+ * Get the dummy fscrypt policy in use on the filesystem (if any).
+ *
+ * Filesystems only need to implement this function if they support the
+ * test_dummy_encryption mount option.
+ *
+ * Return: A pointer to the dummy fscrypt policy, if the filesystem is
+ * mounted with test_dummy_encryption; otherwise NULL.
+ */
const union fscrypt_policy *(*get_dummy_policy)(struct super_block *sb);
+
+ /*
+ * Check whether a directory is empty. i_rwsem will be held for write.
+ */
bool (*empty_dir)(struct inode *inode);
+
+ /* The filesystem's maximum ciphertext filename length, in bytes */
unsigned int max_namelen;
+
+ /*
+ * Check whether the filesystem's inode numbers and UUID are stable,
+ * meaning that they will never be changed even by offline operations
+ * such as filesystem shrinking and therefore can be used in the
+ * encryption without the possibility of files becoming unreadable.
+ *
+ * Filesystems only need to implement this function if they want to
+ * support the FSCRYPT_POLICY_FLAG_IV_INO_LBLK_{32,64} flags. These
+ * flags are designed to work around the limitations of UFS and eMMC
+ * inline crypto hardware, and they shouldn't be used in scenarios where
+ * such hardware isn't being used.
+ *
+ * Leaving this NULL is equivalent to always returning false.
+ */
bool (*has_stable_inodes)(struct super_block *sb);
+
+ /*
+ * Get the number of bits that the filesystem uses to represent inode
+ * numbers and file logical block numbers.
+ *
+ * By default, both of these are assumed to be 64-bit. This function
+ * can be implemented to declare that either or both of these numbers is
+ * shorter, which may allow the use of the
+ * FSCRYPT_POLICY_FLAG_IV_INO_LBLK_{32,64} flags and/or the use of
+ * inline crypto hardware whose maximum DUN length is less than 64 bits
+ * (e.g., eMMC v5.2 spec compliant hardware). This function only needs
+ * to be implemented if support for one of these features is needed.
+ */
void (*get_ino_and_lblk_bits)(struct super_block *sb,
int *ino_bits_ret, int *lblk_bits_ret);
+
+ /*
+ * Return the number of block devices to which the filesystem may write
+ * encrypted file contents.
+ *
+ * If the filesystem can use multiple block devices (other than block
+ * devices that aren't used for encrypted file contents, such as
+ * external journal devices), and wants to support inline encryption,
+ * then it must implement this function. Otherwise it's not needed.
+ */
int (*get_num_devices)(struct super_block *sb);
+
+ /*
+ * If ->get_num_devices() returns a value greater than 1, then this
+ * function is called to get the array of request_queues that the
+ * filesystem is using -- one per block device. (There may be duplicate
+ * entries in this array, as block devices can share a request_queue.)
+ */
void (*get_devices)(struct super_block *sb,
struct request_queue **devs);
};
--
2.32.0
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