Re: [Qemu-devel] [V9fs-developer] [Bug 1336794] Re: 9pfs does not honor open file handles on unlinked files

[Eric Van Hensbergen <ericvh@gmail.com>]

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That patch looks fine by me.  Happy to put it in the queue.  Thanks Al.

On Tue, Apr 14, 2015 at 11:07 AM Al Viro <viro@zeniv.linux.org.uk> wrote:

> On Mon, Apr 13, 2015 at 04:05:28PM +0000, Eric Van Hensbergen wrote:
> > Well, technically fid 3 isn't 'open', only fid 2 is open - at least
> > according to the protocol.  fid 3 and fid 2 are both clones of fid 1.
> > However, thanks for the alternative workaround.  If you get a chance, can
> > you check that my change to the client to partially fix this for the
> other
> > servers doesn't break nfs-ganesha:
> >
> >
> https://github.com/ericvh/linux/commit/fddc7721d6d19e4e6be4905f37ade5b0521f4ed5
>
> BTW, what the hell is going on in v9fs_vfs_mknod() and v9fs_vfs_link()?
> You allocate 4Kb buffer, sprintf into it ("b %u %u", "c %u %u", or "%d\n")
> feed it to v9fs_vfs_mkspecial() and immediately free it.  What's wrong with
> a local array of char?  In the worst case it needs to be char name[24] -
> surely, we are not so tight on stack that extra 16 bytes (that array
> instead
> of a pointer) would drive us over the cliff?
>
> IOW, do you have any problem with this:
> diff --git a/fs/9p/vfs_inode.c b/fs/9p/vfs_inode.c
> index 703342e..cda68f7 100644
> --- a/fs/9p/vfs_inode.c
> +++ b/fs/9p/vfs_inode.c
> @@ -1370,6 +1370,8 @@ v9fs_vfs_symlink(struct inode *dir, struct dentry
> *dentry, const char *symname)
>         return v9fs_vfs_mkspecial(dir, dentry, P9_DMSYMLINK, symname);
>  }
>
> +#define U32_MAX_DIGITS 10
> +
>  /**
>   * v9fs_vfs_link - create a hardlink
>   * @old_dentry: dentry for file to link to
> @@ -1383,7 +1385,7 @@ v9fs_vfs_link(struct dentry *old_dentry, struct
> inode *dir,
>               struct dentry *dentry)
>  {
>         int retval;
> -       char *name;
> +       char name[1 + U32_MAX_DIGITS + 2]; /* sign + number + \n + \0 */
>         struct p9_fid *oldfid;
>
>         p9_debug(P9_DEBUG_VFS, " %lu,%pd,%pd\n",
> @@ -1393,20 +1395,12 @@ v9fs_vfs_link(struct dentry *old_dentry, struct
> inode *dir,
>         if (IS_ERR(oldfid))
>                 return PTR_ERR(oldfid);
>
> -       name = __getname();
> -       if (unlikely(!name)) {
> -               retval = -ENOMEM;
> -               goto clunk_fid;
> -       }
> -
>         sprintf(name, "%d\n", oldfid->fid);
>         retval = v9fs_vfs_mkspecial(dir, dentry, P9_DMLINK, name);
> -       __putname(name);
>         if (!retval) {
>                 v9fs_refresh_inode(oldfid, d_inode(old_dentry));
>                 v9fs_invalidate_inode_attr(dir);
>         }
> -clunk_fid:
>         p9_client_clunk(oldfid);
>         return retval;
>  }
> @@ -1425,7 +1419,7 @@ v9fs_vfs_mknod(struct inode *dir, struct dentry
> *dentry, umode_t mode, dev_t rde
>  {
>         struct v9fs_session_info *v9ses = v9fs_inode2v9ses(dir);
>         int retval;
> -       char *name;
> +       char name[2 + U32_MAX_DIGITS + 1 + U32_MAX_DIGITS + 1];
>         u32 perm;
>
>         p9_debug(P9_DEBUG_VFS, " %lu,%pd mode: %hx MAJOR: %u MINOR: %u\n",
> @@ -1435,26 +1429,16 @@ v9fs_vfs_mknod(struct inode *dir, struct dentry
> *dentry, umode_t mode, dev_t rde
>         if (!new_valid_dev(rdev))
>                 return -EINVAL;
>
> -       name = __getname();
> -       if (!name)
> -               return -ENOMEM;
>         /* build extension */
>         if (S_ISBLK(mode))
>                 sprintf(name, "b %u %u", MAJOR(rdev), MINOR(rdev));
>         else if (S_ISCHR(mode))
>                 sprintf(name, "c %u %u", MAJOR(rdev), MINOR(rdev));
> -       else if (S_ISFIFO(mode))
> -               *name = 0;
> -       else if (S_ISSOCK(mode))
> +       else
>                 *name = 0;
> -       else {
> -               __putname(name);
> -               return -EINVAL;
> -       }
>
>         perm = unixmode2p9mode(v9ses, mode);
>         retval = v9fs_vfs_mkspecial(dir, dentry, perm, name);
> -       __putname(name);
>
>         return retval;
>  }
>

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