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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: Steve French <stfrench@microsoft.com>
Reviewed-by: Ronnie Sahlberg <lsahlber@redhat.com>
This commit is contained in:
Steve French 2018-08-10 02:25:06 -05:00
parent e55954a5f7
commit cdeaf9d04a
2 changed files with 68 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

60
fs/cifs/smb2pdu.c
View File

@ -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;
}

8
fs/cifs/smb2pdu.h
View File

@ -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];