fscrypt: replace get_ino_and_lblk_bits with just has_32bit_inodes

Now that fs/crypto/ computes the filesystem's lblk_bits from its maximum
file size, it is no longer necessary for filesystems to provide
lblk_bits via fscrypt_operations::get_ino_and_lblk_bits.

It is still necessary for fs/crypto/ to retrieve ino_bits from the
filesystem.  However, this is used only to decide whether inode numbers
fit in 32 bits.  Also, ino_bits is static for all relevant filesystems,
i.e. it doesn't depend on the filesystem instance.

Therefore, in the interest of keeping things as simple as possible,
replace 'get_ino_and_lblk_bits' with a flag 'has_32bit_inodes'.  This
can always be changed back to a function if a filesystem needs it to be
dynamic, but for now a static flag is all that's needed.

Link: https://lore.kernel.org/r/20230925055451.59499-5-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>

1 files changed, 11 insertions, 15 deletions

diff --git a/include/linux/fscrypt.h b/include/linux/fscrypt.h
index 4505078e89b7..09a3cacbf62a 100644
--- a/include/linux/fscrypt.h
+++ b/include/linux/fscrypt.h
@@ -75,6 +75,17 @@ struct fscrypt_operations {
 	unsigned int needs_bounce_pages : 1;
 
 	/*
+	 * If set, then fs/crypto/ will allow the use of encryption settings
+	 * that assume inode numbers fit in 32 bits (i.e.
+	 * FSCRYPT_POLICY_FLAG_IV_INO_LBLK_{32,64}), provided that the other
+	 * prerequisites for these settings are also met.  This is only useful
+	 * if the filesystem wants to support inline encryption hardware that is
+	 * limited to 32-bit or 64-bit data unit numbers and where programming
+	 * keyslots is very slow.
+	 */
+	unsigned int has_32bit_inodes : 1;
+
+	/*
 	 * This field exists only for backwards compatibility reasons and should
 	 * only be set by the filesystems that are setting it already.  It
 	 * contains the filesystem-specific key description prefix that is
@@ -152,21 +163,6 @@ struct fscrypt_operations {
 	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 an array of pointers to the block devices to which the
 	 * filesystem may write encrypted file contents, NULL if the filesystem
 	 * only has a single such block device, or an ERR_PTR() on error.