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

fs/crypto/inline_crypt.c

@@ -21,20 +21,22 @@
 
 #include "fscrypt_private.h"
 
-static int fscrypt_get_num_devices(struct super_block *sb)
+static struct block_device **fscrypt_get_devices(struct super_block *sb,
+						 unsigned int *num_devs)
 {
-	if (sb->s_cop->get_num_devices)
-		return sb->s_cop->get_num_devices(sb);
-	return 1;
-}
+	struct block_device **devs;
 
-static void fscrypt_get_devices(struct super_block *sb, int num_devs,
-				struct request_queue **devs)
-{
-	if (num_devs == 1)
-		devs[0] = bdev_get_queue(sb->s_bdev);
-	else
-		sb->s_cop->get_devices(sb, devs);
+	if (sb->s_cop->get_devices) {
+		devs = sb->s_cop->get_devices(sb, num_devs);
+		if (devs)
+			return devs;
+	}
+	devs = kmalloc(sizeof(*devs), GFP_KERNEL);
+	if (!devs)
+		return ERR_PTR(-ENOMEM);
+	devs[0] = sb->s_bdev;
+	*num_devs = 1;
+	return devs;
 }
 
 static unsigned int fscrypt_get_dun_bytes(const struct fscrypt_info *ci)
@@ -68,15 +70,17 @@ static unsigned int fscrypt_get_dun_bytes(const struct fscrypt_info *ci)
  * helpful for debugging problems where the "wrong" implementation is used.
  */
 static void fscrypt_log_blk_crypto_impl(struct fscrypt_mode *mode,
-					struct request_queue **devs,
-					int num_devs,
+					struct block_device **devs,
+					unsigned int num_devs,
 					const struct blk_crypto_config *cfg)
 {
-	int i;
+	unsigned int i;
 
 	for (i = 0; i < num_devs; i++) {
+		struct request_queue *q = bdev_get_queue(devs[i]);
+
 		if (!IS_ENABLED(CONFIG_BLK_INLINE_ENCRYPTION_FALLBACK) ||
-		    __blk_crypto_cfg_supported(devs[i]->crypto_profile, cfg)) {
+		    __blk_crypto_cfg_supported(q->crypto_profile, cfg)) {
 			if (!xchg(&mode->logged_blk_crypto_native, 1))
 				pr_info("fscrypt: %s using blk-crypto (native)\n",
 					mode->friendly_name);
@@ -93,9 +97,9 @@ int fscrypt_select_encryption_impl(struct fscrypt_info *ci)
 	const struct inode *inode = ci->ci_inode;
 	struct super_block *sb = inode->i_sb;
 	struct blk_crypto_config crypto_cfg;
-	int num_devs;
-	struct request_queue **devs;
-	int i;
+	struct block_device **devs;
+	unsigned int num_devs;
+	unsigned int i;
 
 	/* The file must need contents encryption, not filenames encryption */
 	if (!S_ISREG(inode->i_mode))
@@ -123,20 +127,20 @@ int fscrypt_select_encryption_impl(struct fscrypt_info *ci)
 		return 0;
 
 	/*
-	 * On all the filesystem's devices, blk-crypto must support the crypto
-	 * configuration that the file would use.
+	 * On all the filesystem's block devices, blk-crypto must support the
+	 * crypto configuration that the file would use.
 	 */
 	crypto_cfg.crypto_mode = ci->ci_mode->blk_crypto_mode;
 	crypto_cfg.data_unit_size = sb->s_blocksize;
 	crypto_cfg.dun_bytes = fscrypt_get_dun_bytes(ci);
-	num_devs = fscrypt_get_num_devices(sb);
-	devs = kmalloc_array(num_devs, sizeof(*devs), GFP_KERNEL);
-	if (!devs)
-		return -ENOMEM;
-	fscrypt_get_devices(sb, num_devs, devs);
+
+	devs = fscrypt_get_devices(sb, &num_devs);
+	if (IS_ERR(devs))
+		return PTR_ERR(devs);
 
 	for (i = 0; i < num_devs; i++) {
-		if (!blk_crypto_config_supported(devs[i], &crypto_cfg))
+		if (!blk_crypto_config_supported(bdev_get_queue(devs[i]),
+						 &crypto_cfg))
 			goto out_free_devs;
 	}
 
@@ -157,7 +161,7 @@ int fscrypt_prepare_inline_crypt_key(struct fscrypt_prepared_key *prep_key,
 	struct super_block *sb = inode->i_sb;
 	enum blk_crypto_mode_num crypto_mode = ci->ci_mode->blk_crypto_mode;
 	struct blk_crypto_key *blk_key;
-	struct request_queue **devs;
+	struct block_device **devs;
 	unsigned int num_devs;
 	unsigned int i;
 	int err;
@@ -174,15 +178,14 @@ int fscrypt_prepare_inline_crypt_key(struct fscrypt_prepared_key *prep_key,
 	}
 
 	/* Start using blk-crypto on all the filesystem's block devices. */
-	num_devs = fscrypt_get_num_devices(sb);
-	devs = kmalloc_array(num_devs, sizeof(*devs), GFP_KERNEL);
-	if (!devs) {
-		err = -ENOMEM;
+	devs = fscrypt_get_devices(sb, &num_devs);
+	if (IS_ERR(devs)) {
+		err = PTR_ERR(devs);
 		goto fail;
 	}
-	fscrypt_get_devices(sb, num_devs, devs);
 	for (i = 0; i < num_devs; i++) {
-		err = blk_crypto_start_using_key(blk_key, devs[i]);
+		err = blk_crypto_start_using_key(blk_key,
+						 bdev_get_queue(devs[i]));
 		if (err)
 			break;
 	}
@@ -210,7 +213,7 @@ void fscrypt_destroy_inline_crypt_key(struct super_block *sb,
 				      struct fscrypt_prepared_key *prep_key)
 {
 	struct blk_crypto_key *blk_key = prep_key->blk_key;
-	struct request_queue **devs;
+	struct block_device **devs;
 	unsigned int num_devs;
 	unsigned int i;
 
@@ -218,12 +221,10 @@ void fscrypt_destroy_inline_crypt_key(struct super_block *sb,
 		return;
 
 	/* Evict the key from all the filesystem's block devices. */
-	num_devs = fscrypt_get_num_devices(sb);
-	devs = kmalloc_array(num_devs, sizeof(*devs), GFP_KERNEL);
-	if (devs) {
-		fscrypt_get_devices(sb, num_devs, devs);
+	devs = fscrypt_get_devices(sb, &num_devs);
+	if (!IS_ERR(devs)) {
 		for (i = 0; i < num_devs; i++)
-			blk_crypto_evict_key(devs[i], blk_key);
+			blk_crypto_evict_key(bdev_get_queue(devs[i]), blk_key);
 		kfree(devs);
 	}
 	kfree_sensitive(blk_key);

fs/f2fs/super.c

@@ -3039,23 +3039,24 @@ static void f2fs_get_ino_and_lblk_bits(struct super_block *sb,
 	*lblk_bits_ret = 8 * sizeof(block_t);
 }
 
-static int f2fs_get_num_devices(struct super_block *sb)
-{
-	struct f2fs_sb_info *sbi = F2FS_SB(sb);
-
-	if (f2fs_is_multi_device(sbi))
-		return sbi->s_ndevs;
-	return 1;
-}
-
-static void f2fs_get_devices(struct super_block *sb,
-			     struct request_queue **devs)
+static struct block_device **f2fs_get_devices(struct super_block *sb,
+					      unsigned int *num_devs)
 {
 	struct f2fs_sb_info *sbi = F2FS_SB(sb);
+	struct block_device **devs;
 	int i;
 
+	if (!f2fs_is_multi_device(sbi))
+		return NULL;
+
+	devs = kmalloc_array(sbi->s_ndevs, sizeof(*devs), GFP_KERNEL);
+	if (!devs)
+		return ERR_PTR(-ENOMEM);
+
 	for (i = 0; i < sbi->s_ndevs; i++)
-		devs[i] = bdev_get_queue(FDEV(i).bdev);
+		devs[i] = FDEV(i).bdev;
+	*num_devs = sbi->s_ndevs;
+	return devs;
 }
 
 static const struct fscrypt_operations f2fs_cryptops = {
@@ -3066,7 +3067,6 @@ static const struct fscrypt_operations f2fs_cryptops = {
 	.empty_dir		= f2fs_empty_dir,
 	.has_stable_inodes	= f2fs_has_stable_inodes,
 	.get_ino_and_lblk_bits	= f2fs_get_ino_and_lblk_bits,
-	.get_num_devices	= f2fs_get_num_devices,
 	.get_devices		= f2fs_get_devices,
 };
 #endif

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)