Commit cdeaf9d0 authored by Steve French's avatar Steve French
Browse files

smb3: allow previous versions to be mounted with snapshot= mount parm 



mounting with the "snapshots=" mount parm allows a read-only
view of a previous version of a file system (see MS-SMB2
and "timewarp" tokens, section 2.2.13.2.6) based on the timestamp
passed in on the snapshots mount parm.

Add processing to optionally send this create context.

Example output:

/mnt1 is mounted with "snapshots=..." and will see an earlier
version of the directory, with three fewer files than /mnt2
the current version of the directory.

root@Ubuntu-17-Virtual-Machine:~/cifs-2.6# cat /proc/mounts | grep cifs
//172.22.149.186/public /mnt1 cifs
ro,relatime,vers=default,cache=strict,username=smfrench,uid=0,noforceuid,gid=0,noforcegid,addr=172.22.149.186,file_mode=0755,dir_mode=0755,soft,nounix,mapposix,rsize=1048576,wsize=1048576,echo_interval=60,snapshot=131748608570000000,actimeo=1

//172.22.149.186/public /mnt2 cifs
rw,relatime,vers=default,cache=strict,username=smfrench,uid=0,noforceuid,gid=0,noforcegid,addr=172.22.149.186,file_mode=0755,dir_mode=0755,soft,nounix,mapposix,rsize=1048576,wsize=1048576,echo_interval=60,actimeo=1

root@Ubuntu-17-Virtual-Machine:~/cifs-2.6# ls /mnt1
EmptyDir  newerdir
root@Ubuntu-17-Virtual-Machine:~/cifs-2.6# ls /mnt1/newerdir

root@Ubuntu-17-Virtual-Machine:~/cifs-2.6# ls /mnt2
EmptyDir  file  newerdir  newestdir  timestamp-trace.cap
root@Ubuntu-17-Virtual-Machine:~/cifs-2.6# ls /mnt2/newerdir
new-file-not-in-snapshot

Snapshots are extremely useful for comparing previous versions of files or directories,
and recovering from data corruptions or mistakes.

Signed-off-by: default avatarSteve French <stfrench@microsoft.com>
Reviewed-by: default avatarRonnie Sahlberg <lsahlber@redhat.com>
parent e55954a5

fs/cifs/smb2pdu.c

+60 −0
Original line number Diff line number Diff line
@@ -1856,6 +1856,51 @@ add_durable_context(struct kvec *iov, unsigned int *num_iovec, 
	return 0;

}



/* See MS-SMB2 2.2.13.2.7 */

static struct crt_twarp_ctxt *

create_twarp_buf(__u64 timewarp)

{

	struct crt_twarp_ctxt *buf;



	buf = kzalloc(sizeof(struct crt_twarp_ctxt), GFP_KERNEL);

	if (!buf)

		return NULL;



	buf->ccontext.DataOffset = cpu_to_le16(offsetof

					(struct crt_twarp_ctxt, Timestamp));

	buf->ccontext.DataLength = cpu_to_le32(8);

	buf->ccontext.NameOffset = cpu_to_le16(offsetof

				(struct crt_twarp_ctxt, Name));

	buf->ccontext.NameLength = cpu_to_le16(4);

	/* SMB2_CREATE_TIMEWARP_TOKEN is "TWrp" */

	buf->Name[0] = 'T';

	buf->Name[1] = 'W';

	buf->Name[2] = 'r';

	buf->Name[3] = 'p';

	buf->Timestamp = cpu_to_le64(timewarp);

	return buf;

}



/* See MS-SMB2 2.2.13.2.7 */

static int

add_twarp_context(struct kvec *iov, unsigned int *num_iovec, __u64 timewarp)

{

	struct smb2_create_req *req = iov[0].iov_base;

	unsigned int num = *num_iovec;



	iov[num].iov_base = create_twarp_buf(timewarp);

	if (iov[num].iov_base == NULL)

		return -ENOMEM;

	iov[num].iov_len = sizeof(struct crt_twarp_ctxt);

	if (!req->CreateContextsOffset)

		req->CreateContextsOffset = cpu_to_le32(

				sizeof(struct smb2_create_req) +

				iov[num - 1].iov_len);

	le32_add_cpu(&req->CreateContextsLength, sizeof(struct crt_twarp_ctxt));

	*num_iovec = num + 1;

	return 0;

}



static int

alloc_path_with_tree_prefix(__le16 **out_path, int *out_size, int *out_len,

			    const char *treename, const __le16 *path)
@@ -2168,6 +2213,21 @@ SMB2_open_init(struct cifs_tcon *tcon, struct smb_rqst *rqst, __u8 *oplock, 
			return rc;

	}



	if (tcon->snapshot_time) {

		cifs_dbg(FYI, "adding snapshot context\n");

		if (n_iov > 2) {

			struct create_context *ccontext =

			    (struct create_context *)iov[n_iov-1].iov_base;

			ccontext->Next =

				cpu_to_le32(iov[n_iov-1].iov_len);

		}



		rc = add_twarp_context(iov, &n_iov, tcon->snapshot_time);

		if (rc)

			return rc;

	}





	rqst->rq_nvec = n_iov;

	return 0;

}

fs/cifs/smb2pdu.h

+8 −0
Original line number Diff line number Diff line
@@ -767,6 +767,14 @@ struct create_durable_handle_reconnect_v2 { 
	struct durable_reconnect_context_v2 dcontext;

} __packed;



/* See MS-SMB2 2.2.13.2.5 */

struct crt_twarp_ctxt {

	struct create_context ccontext;

	__u8	Name[8];

	__le64	Timestamp;



} __packed;



#define COPY_CHUNK_RES_KEY_SIZE	24

struct resume_key_req {

	char ResumeKey[COPY_CHUNK_RES_KEY_SIZE];

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