On Thu, 11 Oct 2012 00:33:48 -0500
Shirish Pargaonkar <shirishpargaonkar@xxxxxxxxx> wrote:
> On Wed, Oct 10, 2012 at 2:05 PM, Jeff Layton <jlayton@xxxxxxxxxx> wrote:
> > On Wed, 10 Oct 2012 13:25:59 -0400
> > Jeff Layton <jlayton@xxxxxxxxxx> wrote:
> >
> >> On Wed, 10 Oct 2012 12:22:16 -0500
> >> Shirish Pargaonkar <shirishpargaonkar@xxxxxxxxx> wrote:
> >>
> >> > On Wed, Oct 10, 2012 at 11:14 AM, Jeff Layton <jlayton@xxxxxxxxxx> wrote:
> >> > > On Wed, 10 Oct 2012 10:11:46 -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.
> >> > >>
> >> > >> One operation that does not work is Rename (0x7).
> >> > >>
> >> > >>
> >> > >> Signed-off-by: Shirish Pargaonkar <shirishpargaonkar@xxxxxxxxx>
> >> > >> ---
> >> > >> fs/cifs/cifsfs.c | 1 +
> >> > >> fs/cifs/cifsglob.h | 2 ++
> >> > >> fs/cifs/inode.c | 33 ++++++++++++++++++++++++++++++++-
> >> > >> 3 files changed, 35 insertions(+), 1 deletions(-)
> >> > >>
> >> > >> diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
> >> > >> index e7931cc..3068992 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..93b010b 100644
> >> > >> --- a/fs/cifs/inode.c
> >> > >> +++ b/fs/cifs/inode.c
> >> > >> @@ -619,6 +619,7 @@ cifs_get_inode_info(struct inode **inode, const char *full_path,
> >> > >> 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);
> >> > >> @@ -746,14 +747,34 @@ cifs_get_inode_info(struct inode **inode, const char *full_path,
> >> > >> }
> >> > >>
> >> > >> if (!*inode) {
> >> > >> + if (strstr(full_path, ":")) {
> >
> > I think you probably want strrchr here. You want to
> > search the string backward. It's possible that the
> > pathname might have multiple ':' characters in it.
> >
> >> > >> + fattr.cf_private = kstrdup(full_path, GFP_KERNEL);
> >
> > Is it really necessary to copy the entire path? This is
> > a frequently traveled bit of code, and I think you
> > could save some cycles by just copying the alternate
> > data stream name.
> >
> >> > >> + 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 (strstr(full_path, ":") &&
> >> > >> + !((*inode)->i_flags & S_PRIVATE)) {
> >> > >> + (*inode)->i_private = kstrdup(fattr.cf_private,
> >> > >> + GFP_KERNEL);
> >> > >> + if ((*inode)->i_private)
> >> > >> + (*inode)->i_flags |= S_PRIVATE;
> >> > >> + else
> >> > >> + rc = -ENOMEM;
> >> > >> + }
> >> > >> + } else
> >> > >> rc = -ENOMEM;
> >> > >> } else {
> >> > >> cifs_fattr_to_inode(*inode, &fattr);
> >> > >> }
> >> > >>
> >> > >> cgii_exit:
> >> > >> + kfree(fattr.cf_private);
> >> > >> kfree(buf);
> >> > >> cifs_put_tlink(tlink);
> >> > >> return rc;
> >> > >> @@ -784,6 +805,16 @@ 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_flags & S_PRIVATE)) {
> >> > >> + return 0;
> >> > >> + } else {
> >> > >> + if (strcmp(inode->i_private, fattr->cf_private))
> >> > >> + return 0;
> >> > >> + }
> >> > >> + }
> >> > >> +
> >> > >> return 1;
> >> > >> }
> >> > >>
> >> > >
> >
> >
> > At least in my cursory testing, it's possible to create an alternate
> > data stream on a directory as well as a file. The resulting inode does
> > not seem to be treated as a directory, but what are the implications if
> > a particular server does?
>
> Which server would that be? Do you mean like, can you create a
> parallel alternate data stream directory which can get populated with
> files (with alternate data streams)? It is probably not possible,
> an alternate data stream for a directory is used just the way one
> is used for a file.
>
> >
> > Also, what's the interaction here with "mapchars" mount option? If
> > someone specifies that, what behavior should they expect wrt alternate
> > data streams?
>
> It is same as if you were to mount without mapchars mount option.
> If you mount with mapchars option and create alternate data streams, they
> are accessible only with mapchars mount option.
>
':' is one of the characters remapped when you specify mapchars, so I
don't think it's something you can ignore.
--
Jeff Layton <jlayton@xxxxxxxxxx>
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