From 85097d72d3d993cbfc62bcdb206a96ce2268dae1 Mon Sep 17 00:00:00 2001
From: Steve French <stfrench@microsoft.com>
Date: Fri, 10 Aug 2018 02:25:06 -0500
Subject: [PATCH] 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>
---
fs/cifs/smb2pdu.c | 60 +++++++++++++++++++++++++++++++++++++++++++++++
fs/cifs/smb2pdu.h | 8 +++++++
2 files changed, 68 insertions(+)
@@ -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;
}
@@ -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];
--
2.17.1
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. See attached patch