Commit 1ef15fbe authored by Rajasi Mandal's avatar Rajasi Mandal Committed by Steve French
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cifs: client: enforce consistent handling of multichannel and max_channels 



Previously, the behavior of the multichannel and max_channels mount
options was inconsistent and order-dependent. For example, specifying
"multichannel,max_channels=1" would result in 2 channels, while
"max_channels=1,multichannel" would result in 1 channel. Additionally,
conflicting combinations such as "nomultichannel,max_channels=3" or
"multichannel,max_channels=1" did not produce errors and could lead to
unexpected channel counts.

This commit introduces two new fields in smb3_fs_context to explicitly
track whether multichannel and max_channels were specified during
mount. The option parsing and validation logic is updated to ensure:
- The outcome is no longer dependent on the order of options.
- Conflicting combinations (e.g., "nomultichannel,max_channels=3" or
  "multichannel,max_channels=1") are detected and result in an error.
- The number of channels created is consistent with the specified
  options.

This improves the reliability and predictability of mount option
handling for SMB3 multichannel support.

Reviewed-by: default avatarShyam Prasad N <sprasad@microsoft.com>
Signed-off-by: default avatarRajasi Mandal <rajasimandal@microsoft.com>
Signed-off-by: default avatarSteve French <stfrench@microsoft.com>
parent 86973754

fs/smb/client/cifsfs.c

+0 −1
Original line number Diff line number Diff line
@@ -1016,7 +1016,6 @@ cifs_smb3_do_mount(struct file_system_type *fs_type, 
	} else {

		cifs_info("Attempting to mount %s\n", old_ctx->source);

	}



	cifs_sb = kzalloc(sizeof(*cifs_sb), GFP_KERNEL);

	if (!cifs_sb)

		return ERR_PTR(-ENOMEM);

fs/smb/client/fs_context.c

+48 −17
Original line number Diff line number Diff line
@@ -711,6 +711,47 @@ smb3_parse_devname(const char *devname, struct smb3_fs_context *ctx) 
	return 0;

}



static int smb3_handle_conflicting_options(struct fs_context *fc)

{

	struct smb3_fs_context *ctx = smb3_fc2context(fc);



	if (ctx->multichannel_specified) {

		if (ctx->multichannel) {

			if (!ctx->max_channels_specified) {

				ctx->max_channels = 2;

			} else if (ctx->max_channels == 1) {

				cifs_errorf(fc,

					    "max_channels must be greater than 1 when multichannel is enabled\n");

				return -EINVAL;

			}

		} else {

			if (!ctx->max_channels_specified) {

				ctx->max_channels = 1;

			} else if (ctx->max_channels > 1) {

				cifs_errorf(fc,

					    "max_channels must be equal to 1 when multichannel is disabled\n");

				return -EINVAL;

			}

		}

	} else {

		if (ctx->max_channels_specified) {

			if (ctx->max_channels > 1)

				ctx->multichannel = true;

			else

				ctx->multichannel = false;

		} else {

			ctx->multichannel = false;

			ctx->max_channels = 1;

		}

	}



	//resetting default values as remount doesn't initialize fs_context again

	ctx->multichannel_specified = false;

	ctx->max_channels_specified = false;



	return 0;

}



static void smb3_fs_context_free(struct fs_context *fc);

static int smb3_fs_context_parse_param(struct fs_context *fc,

				       struct fs_parameter *param);
@@ -784,6 +825,7 @@ static int smb3_fs_context_parse_monolithic(struct fs_context *fc, 
		if (ret < 0)

			break;

	}

	ret = smb3_handle_conflicting_options(fc);



	return ret;

}
@@ -1250,15 +1292,11 @@ static int smb3_fs_context_parse_param(struct fs_context *fc, 
		ctx->nodelete = 1;

		break;

	case Opt_multichannel:

		if (result.negated) {

		ctx->multichannel_specified = true;

		if (result.negated)

			ctx->multichannel = false;

			ctx->max_channels = 1;

		} else {

		else

			ctx->multichannel = true;

			/* if number of channels not specified, default to 2 */

			if (ctx->max_channels < 2)

				ctx->max_channels = 2;

		}

		break;

	case Opt_uid:

		ctx->linux_uid = result.uid;
@@ -1394,15 +1432,13 @@ static int smb3_fs_context_parse_param(struct fs_context *fc, 
		ctx->max_credits = result.uint_32;

		break;

	case Opt_max_channels:

		ctx->max_channels_specified = true;

		if (result.uint_32 < 1 || result.uint_32 > CIFS_MAX_CHANNELS) {

			cifs_errorf(fc, "%s: Invalid max_channels value, needs to be 1-%d\n",

				 __func__, CIFS_MAX_CHANNELS);

			goto cifs_parse_mount_err;

		}

		ctx->max_channels = result.uint_32;

		/* If more than one channel requested ... they want multichan */

		if (result.uint_32 > 1)

			ctx->multichannel = true;

		break;

	case Opt_max_cached_dirs:

		if (result.uint_32 < 1) {
@@ -1820,13 +1856,6 @@ static int smb3_fs_context_parse_param(struct fs_context *fc, 
		goto cifs_parse_mount_err;

	}



	/*

	 * Multichannel is not meaningful if max_channels is 1.

	 * Force multichannel to false to ensure consistent configuration.

	 */

	if (ctx->multichannel && ctx->max_channels == 1)

		ctx->multichannel = false;



	return 0;



 cifs_parse_mount_err:
@@ -1913,6 +1942,8 @@ int smb3_init_fs_context(struct fs_context *fc) 


	/* default to no multichannel (single server connection) */

	ctx->multichannel = false;

	ctx->multichannel_specified = false;

	ctx->max_channels_specified = false;

	ctx->max_channels = 1;



	ctx->backupuid_specified = false; /* no backup intent for a user */

fs/smb/client/fs_context.h

+2 −0
Original line number Diff line number Diff line
@@ -294,6 +294,8 @@ struct smb3_fs_context { 
	bool domainauto:1;

	bool rdma:1;

	bool multichannel:1;

	bool multichannel_specified:1; /* true if user specified multichannel or nomultichannel */

	bool max_channels_specified:1; /* true if user specified max_channels */

	bool use_client_guid:1;

	/* reuse existing guid for multichannel */

	u8 client_guid[SMB2_CLIENT_GUID_SIZE];