On Tue, 23 Oct 2012 08:24:51 -0500
shirishpargaonkar@xxxxxxxxx wrote:
> From: Shirish Pargaonkar <shirishpargaonkar@xxxxxxxxx>
>
>
> 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@xxxxxxxxx>
> ---
> 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@xxxxxxxxxx>
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