fscrypt: work on block_devices instead of request_queues

request_queues are a block layer implementation detail that should not
leak into file systems.  Change the fscrypt inline crypto code to
retrieve block devices instead of request_queues from the file system.
As part of that, clean up the interaction with multi-device file systems
by returning both the number of devices and the actual device array in a
single method call.

Signed-off-by: Christoph Hellwig <hch@lst.de>
[ebiggers: bug fixes and minor tweaks]
Signed-off-by: Eric Biggers <ebiggers@google.com>
Link: https://lore.kernel.org/r/20220901193208.138056-4-ebiggers@kernel.org

1 files changed, 9 insertions, 12 deletions

diff --git a/include/linux/fscrypt.h b/include/linux/fscrypt.h
index db5bb5650bf2..1f12ebb4a69d 100644
--- a/include/linux/fscrypt.h
+++ b/include/linux/fscrypt.h
@@ -161,24 +161,21 @@ struct fscrypt_operations {
 				      int *ino_bits_ret, int *lblk_bits_ret);
 
 	/*
-	 * Return the number of block devices to which the filesystem may write
-	 * encrypted file contents.
+	 * 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.
+	 *
+	 * On successful non-NULL return, *num_devs is set to the number of
+	 * devices in the returned array.  The caller must free the returned
+	 * array using kfree().
 	 *
 	 * 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);
+	struct block_device **(*get_devices)(struct super_block *sb,
+					     unsigned int *num_devs);
 };
 
 static inline struct fscrypt_info *fscrypt_get_info(const struct inode *inode)