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cifs: reduce roundtrips on create/qinfo requests
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To work around some Window servers that return
STATUS_OBJECT_NAME_INVALID on query infos under DFS namespaces that
contain non-ASCII characters, we started checking for -ENOENT on every
file open, and if so, then send additional requests to figure out
whether it is a DFS link or not.  It means that all those requests
will be sent to every non-existing file.

So, in order to reduce the number of roundtrips, check earlier whether
status code is STATUS_OBJECT_NAME_INVALID and tcon supports dfs, and
if so, then map -ENOENT to -EREMOTE so mount or automount will take
care of chasing the DFS link -- if it isn't an DFS link, then -ENOENT
will be returned appropriately.

Before patch

  SMB2 438 Create Request File: ada.test\dfs\foo;GetInfo Request...
  SMB2 310 Create Response, Error: STATUS_OBJECT_NAME_NOT_FOUND;...
  SMB2 228 Ioctl Request FSCTL_DFS_GET_REFERRALS, File: \ada.test\dfs\foo
  SMB2 143 Ioctl Response, Error: STATUS_OBJECT_PATH_NOT_FOUND
  SMB2 438 Create Request File: ada.test\dfs\foo;GetInfo Request...
  SMB2 310 Create Response, Error: STATUS_OBJECT_NAME_NOT_FOUND;...
  SMB2 228 Ioctl Request FSCTL_DFS_GET_REFERRALS, File: \ada.test\dfs\foo
  SMB2 143 Ioctl Response, Error: STATUS_OBJECT_PATH_NOT_FOUND

After patch

  SMB2 438 Create Request File: ada.test\dfs\foo;GetInfo Request...
  SMB2 310 Create Response, Error: STATUS_OBJECT_NAME_NOT_FOUND;...
  SMB2 438 Create Request File: ada.test\dfs\foo;GetInfo Request...
  SMB2 310 Create Response, Error: STATUS_OBJECT_NAME_NOT_FOUND;...

Signed-off-by: Paulo Alcantara (SUSE) <pc@cjr.nz>
Signed-off-by: Steve French <stfrench@microsoft.com>
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Paulo Alcantara authored and Steve French committed Dec 19, 2022
1 parent 86fe0fa commit c877ce4
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Showing 5 changed files with 57 additions and 84 deletions.
16 changes: 0 additions & 16 deletions fs/cifs/connect.c
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Original file line number Diff line number Diff line change
Expand Up @@ -3547,9 +3547,6 @@ static int is_path_remote(struct mount_ctx *mnt_ctx)
struct cifs_tcon *tcon = mnt_ctx->tcon;
struct smb3_fs_context *ctx = mnt_ctx->fs_ctx;
char *full_path;
#ifdef CONFIG_CIFS_DFS_UPCALL
bool nodfs = cifs_sb->mnt_cifs_flags & CIFS_MOUNT_NO_DFS;
#endif

if (!server->ops->is_path_accessible)
return -EOPNOTSUPP;
Expand All @@ -3566,19 +3563,6 @@ static int is_path_remote(struct mount_ctx *mnt_ctx)

rc = server->ops->is_path_accessible(xid, tcon, cifs_sb,
full_path);
#ifdef CONFIG_CIFS_DFS_UPCALL
if (nodfs) {
if (rc == -EREMOTE)
rc = -EOPNOTSUPP;
goto out;
}

/* path *might* exist with non-ASCII characters in DFS root
* try again with full path (only if nodfs is not set) */
if (rc == -ENOENT && is_tcon_dfs(tcon))
rc = cifs_dfs_query_info_nonascii_quirk(xid, tcon, cifs_sb,
full_path);
#endif
if (rc != 0 && rc != -EREMOTE)
goto out;

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6 changes: 0 additions & 6 deletions fs/cifs/inode.c
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Original file line number Diff line number Diff line change
Expand Up @@ -993,12 +993,6 @@ int cifs_get_inode_info(struct inode **inode, const char *full_path,
}
rc = server->ops->query_path_info(xid, tcon, cifs_sb, full_path, &tmp_data,
&adjust_tz, &is_reparse_point);
#ifdef CONFIG_CIFS_DFS_UPCALL
if (rc == -ENOENT && is_tcon_dfs(tcon))
rc = cifs_dfs_query_info_nonascii_quirk(xid, tcon,
cifs_sb,
full_path);
#endif
data = &tmp_data;
}

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45 changes: 0 additions & 45 deletions fs/cifs/misc.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1314,49 +1314,4 @@ int cifs_update_super_prepath(struct cifs_sb_info *cifs_sb, char *prefix)
cifs_sb->mnt_cifs_flags |= CIFS_MOUNT_USE_PREFIX_PATH;
return 0;
}

/** cifs_dfs_query_info_nonascii_quirk
* Handle weird Windows SMB server behaviour. It responds with
* STATUS_OBJECT_NAME_INVALID code to SMB2 QUERY_INFO request
* for "\<server>\<dfsname>\<linkpath>" DFS reference,
* where <dfsname> contains non-ASCII unicode symbols.
*
* Check such DFS reference.
*/
int cifs_dfs_query_info_nonascii_quirk(const unsigned int xid,
struct cifs_tcon *tcon,
struct cifs_sb_info *cifs_sb,
const char *linkpath)
{
char *treename, *dfspath, sep;
int treenamelen, linkpathlen, rc;

treename = tcon->tree_name;
/* MS-DFSC: All paths in REQ_GET_DFS_REFERRAL and RESP_GET_DFS_REFERRAL
* messages MUST be encoded with exactly one leading backslash, not two
* leading backslashes.
*/
sep = CIFS_DIR_SEP(cifs_sb);
if (treename[0] == sep && treename[1] == sep)
treename++;
linkpathlen = strlen(linkpath);
treenamelen = strnlen(treename, MAX_TREE_SIZE + 1);
dfspath = kzalloc(treenamelen + linkpathlen + 1, GFP_KERNEL);
if (!dfspath)
return -ENOMEM;
if (treenamelen)
memcpy(dfspath, treename, treenamelen);
memcpy(dfspath + treenamelen, linkpath, linkpathlen);
rc = dfs_cache_find(xid, tcon->ses, cifs_sb->local_nls,
cifs_remap(cifs_sb), dfspath, NULL, NULL);
if (rc == 0) {
cifs_dbg(FYI, "DFS ref '%s' is found, emulate -EREMOTE\n",
dfspath);
rc = -EREMOTE;
} else {
cifs_dbg(FYI, "%s: dfs_cache_find returned %d\n", __func__, rc);
}
kfree(dfspath);
return rc;
}
#endif
46 changes: 33 additions & 13 deletions fs/cifs/smb2inode.c
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Original file line number Diff line number Diff line change
Expand Up @@ -556,22 +556,42 @@ int smb2_query_path_info(const unsigned int xid, struct cifs_tcon *tcon,
rc = smb2_compound_op(xid, tcon, cifs_sb, full_path, FILE_READ_ATTRIBUTES, FILE_OPEN,
create_options, ACL_NO_MODE, data, SMB2_OP_QUERY_INFO, cfile,
NULL, NULL, err_iov, err_buftype);
if (rc == -EOPNOTSUPP) {
if (err_iov[0].iov_base && err_buftype[0] != CIFS_NO_BUFFER &&
((struct smb2_hdr *)err_iov[0].iov_base)->Command == SMB2_CREATE &&
((struct smb2_hdr *)err_iov[0].iov_base)->Status == STATUS_STOPPED_ON_SYMLINK) {
rc = smb2_parse_symlink_response(cifs_sb, err_iov, &data->symlink_target);
if (rc) {
struct smb2_hdr *hdr = err_iov[0].iov_base;

if (unlikely(!hdr || err_buftype[0] == CIFS_NO_BUFFER))
goto out;
if (rc == -EOPNOTSUPP && hdr->Command == SMB2_CREATE &&
hdr->Status == STATUS_STOPPED_ON_SYMLINK) {
rc = smb2_parse_symlink_response(cifs_sb, err_iov,
&data->symlink_target);
if (rc)
goto out;
}
*reparse = true;
create_options |= OPEN_REPARSE_POINT;

/* Failed on a symbolic link - query a reparse point info */
cifs_get_readable_path(tcon, full_path, &cfile);
rc = smb2_compound_op(xid, tcon, cifs_sb, full_path, FILE_READ_ATTRIBUTES,
FILE_OPEN, create_options, ACL_NO_MODE, data,
SMB2_OP_QUERY_INFO, cfile, NULL, NULL, NULL, NULL);
*reparse = true;
create_options |= OPEN_REPARSE_POINT;

/* Failed on a symbolic link - query a reparse point info */
cifs_get_readable_path(tcon, full_path, &cfile);
rc = smb2_compound_op(xid, tcon, cifs_sb, full_path,
FILE_READ_ATTRIBUTES, FILE_OPEN,
create_options, ACL_NO_MODE, data,
SMB2_OP_QUERY_INFO, cfile, NULL, NULL,
NULL, NULL);
goto out;
} else if (rc != -EREMOTE && IS_ENABLED(CONFIG_CIFS_DFS_UPCALL) &&
hdr->Status == STATUS_OBJECT_NAME_INVALID) {
/*
* Handle weird Windows SMB server behaviour. It responds with
* STATUS_OBJECT_NAME_INVALID code to SMB2 QUERY_INFO request
* for "\<server>\<dfsname>\<linkpath>" DFS reference,
* where <dfsname> contains non-ASCII unicode symbols.
*/
rc = -EREMOTE;
}
if (rc == -EREMOTE && IS_ENABLED(CONFIG_CIFS_DFS_UPCALL) && cifs_sb &&
(cifs_sb->mnt_cifs_flags & CIFS_MOUNT_NO_DFS))
rc = -EOPNOTSUPP;
}

out:
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28 changes: 24 additions & 4 deletions fs/cifs/smb2ops.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -796,7 +796,9 @@ smb2_is_path_accessible(const unsigned int xid, struct cifs_tcon *tcon,
int rc;
__le16 *utf16_path;
__u8 oplock = SMB2_OPLOCK_LEVEL_NONE;
int err_buftype = CIFS_NO_BUFFER;
struct cifs_open_parms oparms;
struct kvec err_iov = {};
struct cifs_fid fid;
struct cached_fid *cfid;

Expand All @@ -820,14 +822,32 @@ smb2_is_path_accessible(const unsigned int xid, struct cifs_tcon *tcon,
oparms.fid = &fid;
oparms.reconnect = false;

rc = SMB2_open(xid, &oparms, utf16_path, &oplock, NULL, NULL, NULL,
NULL);
rc = SMB2_open(xid, &oparms, utf16_path, &oplock, NULL, NULL,
&err_iov, &err_buftype);
if (rc) {
kfree(utf16_path);
return rc;
struct smb2_hdr *hdr = err_iov.iov_base;

if (unlikely(!hdr || err_buftype == CIFS_NO_BUFFER))
goto out;
/*
* Handle weird Windows SMB server behaviour. It responds with
* STATUS_OBJECT_NAME_INVALID code to SMB2 QUERY_INFO request
* for "\<server>\<dfsname>\<linkpath>" DFS reference,
* where <dfsname> contains non-ASCII unicode symbols.
*/
if (rc != -EREMOTE && IS_ENABLED(CONFIG_CIFS_DFS_UPCALL) &&
hdr->Status == STATUS_OBJECT_NAME_INVALID)
rc = -EREMOTE;
if (rc == -EREMOTE && IS_ENABLED(CONFIG_CIFS_DFS_UPCALL) && cifs_sb &&
(cifs_sb->mnt_cifs_flags & CIFS_MOUNT_NO_DFS))
rc = -EOPNOTSUPP;
goto out;
}

rc = SMB2_close(xid, tcon, fid.persistent_fid, fid.volatile_fid);

out:
free_rsp_buf(err_buftype, err_iov.iov_base);
kfree(utf16_path);
return rc;
}
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