[PATCH v6 1/2] cifs: Alternate Data Streams: Add support

[PATCH v6 1/2] cifs: Alternate Data Streams: Add support

[shirishpargaonkar-Re5JQEeQqe8AvxtiuMwx3w]

From: Shirish Pargaonkar <shirishpargaonkar-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>


Add support of Alternate Data Streams (ads).

The generic access flags that cifs client currently employs are sufficient
for alternate data streams as well (MS-CIFS 2.2.4.64.1).

The stream file and stream type are specified using : after the file name,
so that is used to differentiate between a regular file and its
alternate data streams and stream types.
Since they all have the same file id, each path name,
file name:stream name:stream type, has a separate inode with that same
file id but a distinct private data (path name) in that inode to
distinguish them.

This scheme applies only to non-posix compliant servers such as Windows.

One operation that does not work is Rename (0x7).


Signed-off-by: Shirish Pargaonkar <shirishpargaonkar-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
---
 fs/cifs/cifsfs.c   |    1 +
 fs/cifs/cifsglob.h |    2 ++
 fs/cifs/inode.c    |   31 ++++++++++++++++++++++++++++++-
 3 files changed, 33 insertions(+), 1 deletions(-)

diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
index a41044a..1a02c81 100644
--- a/fs/cifs/cifsfs.c
+++ b/fs/cifs/cifsfs.c
@@ -264,6 +264,7 @@ cifs_evict_inode(struct inode *inode)
 {
 	truncate_inode_pages(&inode->i_data, 0);
 	clear_inode(inode);
+	kfree(inode->i_private);
 	cifs_fscache_release_inode_cookie(inode);
 }
 
diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
index f5af252..26d65c7 100644
--- a/fs/cifs/cifsglob.h
+++ b/fs/cifs/cifsglob.h
@@ -1251,6 +1251,7 @@ struct dfs_info3_param {
 #define CIFS_FATTR_DELETE_PENDING	0x2
 #define CIFS_FATTR_NEED_REVAL		0x4
 #define CIFS_FATTR_INO_COLLISION	0x8
+#define CIFS_FATTR_ALTDATASTR		0x10
 
 struct cifs_fattr {
 	u32		cf_flags;
@@ -1268,6 +1269,7 @@ struct cifs_fattr {
 	struct timespec	cf_atime;
 	struct timespec	cf_mtime;
 	struct timespec	cf_ctime;
+	char		*cf_private;
 };
 
 static inline void free_dfs_info_param(struct dfs_info3_param *param)
diff --git a/fs/cifs/inode.c b/fs/cifs/inode.c
index afdff79..b7c6dcf 100644
--- a/fs/cifs/inode.c
+++ b/fs/cifs/inode.c
@@ -615,10 +615,12 @@ cifs_get_inode_info(struct inode **inode, const char *full_path,
 	struct tcon_link *tlink;
 	struct cifs_sb_info *cifs_sb = CIFS_SB(sb);
 	char *buf = NULL;
+	char *altstr = NULL;
 	bool adjust_tz = false;
 	struct cifs_fattr fattr;
 	struct cifs_search_info *srchinf = NULL;
 
+	fattr.cf_private = NULL;
 	tlink = cifs_sb_tlink(cifs_sb);
 	if (IS_ERR(tlink))
 		return PTR_ERR(tlink);
@@ -746,9 +748,26 @@ cifs_get_inode_info(struct inode **inode, const char *full_path,
 	}
 
 	if (!*inode) {
+		altstr = strchr(full_path, ':');
+		if (altstr) {
+			fattr.cf_private = kstrdup(altstr, GFP_KERNEL);
+			if (!fattr.cf_private) {
+				rc = -ENOMEM;
+				goto cgii_exit;
+			}
+			fattr.cf_flags |= CIFS_FATTR_ALTDATASTR;
+		}
+
 		*inode = cifs_iget(sb, &fattr);
-		if (!*inode)
+		if (*inode) {
+			if (altstr && !((*inode)->i_private))
+				(*inode)->i_private = fattr.cf_private;
+			else
+				kfree(fattr.cf_private);
+		} else {
 			rc = -ENOMEM;
+			kfree(fattr.cf_private);
+		}
 	} else {
 		cifs_fattr_to_inode(*inode, &fattr);
 	}
@@ -784,6 +803,16 @@ cifs_find_inode(struct inode *inode, void *opaque)
 	if (S_ISDIR(inode->i_mode) && !hlist_empty(&inode->i_dentry))
 		fattr->cf_flags |= CIFS_FATTR_INO_COLLISION;
 
+	/* looking for an inode of a alternate data stream (full pathname) */
+	if (fattr->cf_flags & CIFS_FATTR_ALTDATASTR) {
+		if (!(inode->i_private)) {
+			return 0;
+		} else {
+			if (strcmp(inode->i_private, fattr->cf_private))
+				return 0;
+		}
+	}
+
 	return 1;
 }
 
-- 
1.6.0.2

Re: [PATCH v6 1/2] cifs: Alternate Data Streams: Add support

[Jeff Layton]

On Tue, 23 Oct 2012 08:24:51 -0500
shirishpargaonkar-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org wrote:

> From: Shirish Pargaonkar <shirishpargaonkar-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
> 
> 
> Add support of Alternate Data Streams (ads).
> 
> The generic access flags that cifs client currently employs are sufficient
> for alternate data streams as well (MS-CIFS 2.2.4.64.1).
> 
> The stream file and stream type are specified using : after the file name,
> so that is used to differentiate between a regular file and its
> alternate data streams and stream types.
> Since they all have the same file id, each path name,
> file name:stream name:stream type, has a separate inode with that same
> file id but a distinct private data (path name) in that inode to
> distinguish them.
> 
> This scheme applies only to non-posix compliant servers such as Windows.
> 

Question: are alternate data streams really part of the protocol
per-se? Or are they an implementation detail of the exported
filesystem? Is it possible that a (say non-windows) server could export
a filesystem that did allow ':' in a filename without posix extensions?

If so, are we at risk of treating such a file as an alternate data
stream instead of a separate file altogether? Is there a way to
distinguish such a situation?

> One operation that does not work is Rename (0x7).
> 

I'm confused. What does this have to do with rename?

> 
> Signed-off-by: Shirish Pargaonkar <shirishpargaonkar-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
> ---
>  fs/cifs/cifsfs.c   |    1 +
>  fs/cifs/cifsglob.h |    2 ++
>  fs/cifs/inode.c    |   31 ++++++++++++++++++++++++++++++-
>  3 files changed, 33 insertions(+), 1 deletions(-)
> 
> diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
> index a41044a..1a02c81 100644
> --- a/fs/cifs/cifsfs.c
> +++ b/fs/cifs/cifsfs.c
> @@ -264,6 +264,7 @@ cifs_evict_inode(struct inode *inode)
>  {
>  	truncate_inode_pages(&inode->i_data, 0);
>  	clear_inode(inode);
> +	kfree(inode->i_private);
>  	cifs_fscache_release_inode_cookie(inode);
>  }
>  
> diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
> index f5af252..26d65c7 100644
> --- a/fs/cifs/cifsglob.h
> +++ b/fs/cifs/cifsglob.h
> @@ -1251,6 +1251,7 @@ struct dfs_info3_param {
>  #define CIFS_FATTR_DELETE_PENDING	0x2
>  #define CIFS_FATTR_NEED_REVAL		0x4
>  #define CIFS_FATTR_INO_COLLISION	0x8
> +#define CIFS_FATTR_ALTDATASTR		0x10
>  
>  struct cifs_fattr {
>  	u32		cf_flags;
> @@ -1268,6 +1269,7 @@ struct cifs_fattr {
>  	struct timespec	cf_atime;
>  	struct timespec	cf_mtime;
>  	struct timespec	cf_ctime;
> +	char		*cf_private;
>  };
>  
>  static inline void free_dfs_info_param(struct dfs_info3_param *param)
> diff --git a/fs/cifs/inode.c b/fs/cifs/inode.c
> index afdff79..b7c6dcf 100644
> --- a/fs/cifs/inode.c
> +++ b/fs/cifs/inode.c
> @@ -615,10 +615,12 @@ cifs_get_inode_info(struct inode **inode, const char *full_path,
>  	struct tcon_link *tlink;
>  	struct cifs_sb_info *cifs_sb = CIFS_SB(sb);
>  	char *buf = NULL;
> +	char *altstr = NULL;
>  	bool adjust_tz = false;
>  	struct cifs_fattr fattr;
>  	struct cifs_search_info *srchinf = NULL;
>  
> +	fattr.cf_private = NULL;
>  	tlink = cifs_sb_tlink(cifs_sb);
>  	if (IS_ERR(tlink))
>  		return PTR_ERR(tlink);
> @@ -746,9 +748,26 @@ cifs_get_inode_info(struct inode **inode, const char *full_path,
>  	}
>  
>  	if (!*inode) {
> +		altstr = strchr(full_path, ':');
> +		if (altstr) {
> +			fattr.cf_private = kstrdup(altstr, GFP_KERNEL);
> +			if (!fattr.cf_private) {
> +				rc = -ENOMEM;
> +				goto cgii_exit;
> +			}
> +			fattr.cf_flags |= CIFS_FATTR_ALTDATASTR;
> +		}
> +
>  		*inode = cifs_iget(sb, &fattr);
> -		if (!*inode)
> +		if (*inode) {
> +			if (altstr && !((*inode)->i_private))
> +				(*inode)->i_private = fattr.cf_private;
> +			else
> +				kfree(fattr.cf_private);
> +		} else {
>  			rc = -ENOMEM;
> +			kfree(fattr.cf_private);
> +		}
>  	} else {
>  		cifs_fattr_to_inode(*inode, &fattr);
>  	}
> @@ -784,6 +803,16 @@ cifs_find_inode(struct inode *inode, void *opaque)
>  	if (S_ISDIR(inode->i_mode) && !hlist_empty(&inode->i_dentry))
>  		fattr->cf_flags |= CIFS_FATTR_INO_COLLISION;
>  
> +	/* looking for an inode of a alternate data stream (full pathname) */
> +	if (fattr->cf_flags & CIFS_FATTR_ALTDATASTR) {
> +		if (!(inode->i_private)) {
> +			return 0;
> +		} else {
> +			if (strcmp(inode->i_private, fattr->cf_private))
> +				return 0;
> +		}
> +	}
> +
>  	return 1;
>  }
>  


-- 
Jeff Layton <jlayton-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>

Re: [PATCH v6 1/2] cifs: Alternate Data Streams: Add support

[Shirish Pargaonkar]

On Tue, Oct 23, 2012 at 9:41 AM, Jeff Layton <jlayton-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> wrote:
> On Tue, 23 Oct 2012 08:24:51 -0500
> shirishpargaonkar-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org wrote:
>
>> From: Shirish Pargaonkar <shirishpargaonkar-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
>>
>>
>> Add support of Alternate Data Streams (ads).
>>
>> The generic access flags that cifs client currently employs are sufficient
>> for alternate data streams as well (MS-CIFS 2.2.4.64.1).
>>
>> The stream file and stream type are specified using : after the file name,
>> so that is used to differentiate between a regular file and its
>> alternate data streams and stream types.
>> Since they all have the same file id, each path name,
>> file name:stream name:stream type, has a separate inode with that same
>> file id but a distinct private data (path name) in that inode to
>> distinguish them.
>>
>> This scheme applies only to non-posix compliant servers such as Windows.
>>
>
> Question: are alternate data streams really part of the protocol
> per-se? Or are they an implementation detail of the exported
> filesystem? Is it possible that a (say non-windows) server could export
> a filesystem that did allow ':' in a filename without posix extensions?
>
> If so, are we at risk of treating such a file as an alternate data
> stream instead of a separate file altogether? Is there a way to
> distinguish such a situation?
>

Jeff, they are not part of the protocol, part of the implementation
details of the exported file system.

It is possible that a cifs/smb server such as a non-windows
server which does not support posix extensions could export a
file system that does allow ':' in a filename but it would not be a
issue because file ids / unique ids at the server would be different.

>> One operation that does not work is Rename (0x7).
>>
>
> I'm confused. What does this have to do with rename?
>

I was stating the observation that, for a file stream, against
a Windows server, cifs/smb operation of renaming that file stream
either to a regular file or to a another file stream fails.
(whereas create / delete / lookup etc. operations succeed).

>>
>> Signed-off-by: Shirish Pargaonkar <shirishpargaonkar-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
>> ---
>>  fs/cifs/cifsfs.c   |    1 +
>>  fs/cifs/cifsglob.h |    2 ++
>>  fs/cifs/inode.c    |   31 ++++++++++++++++++++++++++++++-
>>  3 files changed, 33 insertions(+), 1 deletions(-)
>>
>> diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
>> index a41044a..1a02c81 100644
>> --- a/fs/cifs/cifsfs.c
>> +++ b/fs/cifs/cifsfs.c
>> @@ -264,6 +264,7 @@ cifs_evict_inode(struct inode *inode)
>>  {
>>       truncate_inode_pages(&inode->i_data, 0);
>>       clear_inode(inode);
>> +     kfree(inode->i_private);
>>       cifs_fscache_release_inode_cookie(inode);
>>  }
>>
>> diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
>> index f5af252..26d65c7 100644
>> --- a/fs/cifs/cifsglob.h
>> +++ b/fs/cifs/cifsglob.h
>> @@ -1251,6 +1251,7 @@ struct dfs_info3_param {
>>  #define CIFS_FATTR_DELETE_PENDING    0x2
>>  #define CIFS_FATTR_NEED_REVAL                0x4
>>  #define CIFS_FATTR_INO_COLLISION     0x8
>> +#define CIFS_FATTR_ALTDATASTR                0x10
>>
>>  struct cifs_fattr {
>>       u32             cf_flags;
>> @@ -1268,6 +1269,7 @@ struct cifs_fattr {
>>       struct timespec cf_atime;
>>       struct timespec cf_mtime;
>>       struct timespec cf_ctime;
>> +     char            *cf_private;
>>  };
>>
>>  static inline void free_dfs_info_param(struct dfs_info3_param *param)
>> diff --git a/fs/cifs/inode.c b/fs/cifs/inode.c
>> index afdff79..b7c6dcf 100644
>> --- a/fs/cifs/inode.c
>> +++ b/fs/cifs/inode.c
>> @@ -615,10 +615,12 @@ cifs_get_inode_info(struct inode **inode, const char *full_path,
>>       struct tcon_link *tlink;
>>       struct cifs_sb_info *cifs_sb = CIFS_SB(sb);
>>       char *buf = NULL;
>> +     char *altstr = NULL;
>>       bool adjust_tz = false;
>>       struct cifs_fattr fattr;
>>       struct cifs_search_info *srchinf = NULL;
>>
>> +     fattr.cf_private = NULL;
>>       tlink = cifs_sb_tlink(cifs_sb);
>>       if (IS_ERR(tlink))
>>               return PTR_ERR(tlink);
>> @@ -746,9 +748,26 @@ cifs_get_inode_info(struct inode **inode, const char *full_path,
>>       }
>>
>>       if (!*inode) {
>> +             altstr = strchr(full_path, ':');
>> +             if (altstr) {
>> +                     fattr.cf_private = kstrdup(altstr, GFP_KERNEL);
>> +                     if (!fattr.cf_private) {
>> +                             rc = -ENOMEM;
>> +                             goto cgii_exit;
>> +                     }
>> +                     fattr.cf_flags |= CIFS_FATTR_ALTDATASTR;
>> +             }
>> +
>>               *inode = cifs_iget(sb, &fattr);
>> -             if (!*inode)
>> +             if (*inode) {
>> +                     if (altstr && !((*inode)->i_private))
>> +                             (*inode)->i_private = fattr.cf_private;
>> +                     else
>> +                             kfree(fattr.cf_private);
>> +             } else {
>>                       rc = -ENOMEM;
>> +                     kfree(fattr.cf_private);
>> +             }
>>       } else {
>>               cifs_fattr_to_inode(*inode, &fattr);
>>       }
>> @@ -784,6 +803,16 @@ cifs_find_inode(struct inode *inode, void *opaque)
>>       if (S_ISDIR(inode->i_mode) && !hlist_empty(&inode->i_dentry))
>>               fattr->cf_flags |= CIFS_FATTR_INO_COLLISION;
>>
>> +     /* looking for an inode of a alternate data stream (full pathname) */
>> +     if (fattr->cf_flags & CIFS_FATTR_ALTDATASTR) {
>> +             if (!(inode->i_private)) {
>> +                     return 0;
>> +             } else {
>> +                     if (strcmp(inode->i_private, fattr->cf_private))
>> +                             return 0;
>> +             }
>> +     }
>> +
>>       return 1;
>>  }
>>
>
>
> --
> Jeff Layton <jlayton-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>