fscrypt: Remove fscrypt_dio_supported()

On block-based filesystems, fscrypt file contents encryption is now
always implemented using blk-crypto.  This implementation supports
direct I/O.

Therefore, fscrypt_dio_supported() now always returns true, except in
the edge case where statx(STATX_DIOALIGN) is called on an encrypted
regular file that hasn't had its key set up.  But that was really a
workaround rather than the desired behavior, so we can disregard it.

Thus, fscrypt_dio_supported() is no longer needed.  Remove it.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://patch.msgid.link/20260713023708.9245-14-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>

1 files changed, 0 insertions, 43 deletions

diff --git a/fs/crypto/inline_crypt.c b/fs/crypto/inline_crypt.c
index 6b90fd5e8fee..57f3496dd36e 100644
--- a/fs/crypto/inline_crypt.c
+++ b/fs/crypto/inline_crypt.c
@@ -287,49 +287,6 @@ bool fscrypt_mergeable_bio(struct bio *bio, const struct inode *inode,
 EXPORT_SYMBOL_GPL(fscrypt_mergeable_bio);
 
 /**
- * fscrypt_dio_supported() - check whether DIO (direct I/O) is supported on an
- *			     inode, as far as encryption is concerned
- * @inode: the inode in question
- *
- * Return: %true if there are no encryption constraints that prevent DIO from
- *	   being supported; %false if DIO is unsupported.  (Note that in the
- *	   %true case, the filesystem might have other, non-encryption-related
- *	   constraints that prevent DIO from actually being supported.  Also, on
- *	   encrypted files the filesystem is still responsible for only allowing
- *	   DIO when requests are filesystem-block-aligned.)
- */
-bool fscrypt_dio_supported(struct inode *inode)
-{
-	int err;
-
-	/* If the file is unencrypted, no veto from us. */
-	if (!fscrypt_needs_contents_encryption(inode))
-		return true;
-
-	/*
-	 * We only support DIO with inline crypto, not fs-layer crypto.
-	 *
-	 * To determine whether the inode is using inline crypto, we have to set
-	 * up the key if it wasn't already done.  This is because in the current
-	 * design of fscrypt, the decision of whether to use inline crypto or
-	 * not isn't made until the inode's encryption key is being set up.  In
-	 * the DIO read/write case, the key will always be set up already, since
-	 * the file will be open.  But in the case of statx(), the key might not
-	 * be set up yet, as the file might not have been opened yet.
-	 */
-	err = fscrypt_require_key(inode);
-	if (err) {
-		/*
-		 * Key unavailable or couldn't be set up.  This edge case isn't
-		 * worth worrying about; just report that DIO is unsupported.
-		 */
-		return false;
-	}
-	return true;
-}
-EXPORT_SYMBOL_GPL(fscrypt_dio_supported);
-
-/**
  * fscrypt_limit_io_blocks() - limit I/O blocks to avoid discontiguous DUNs
  * @inode: the file on which I/O is being done
  * @lblk: the block at which the I/O is being started from