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    Subject[RFC][PATCH 16/20] sys_mknodat(): elevate write count for vfs_mknod/create()
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    This takes care of all of the direct callers of vfs_mknod().
    Since a few of these cases also handle normal file creation
    as well, this also covers some calls to vfs_create().

    Signed-off-by: Dave Hansen <haveblue@us.ibm.com>
    ---

    lxc-dave/fs/namei.c | 12 ++++++++++++
    lxc-dave/fs/nfsd/vfs.c | 4 ++++
    lxc-dave/net/unix/af_unix.c | 4 ++++
    3 files changed, 20 insertions(+)

    diff -puN fs/namei.c~C-elevate-writers-vfs_mknod-try2 fs/namei.c
    --- lxc/fs/namei.c~C-elevate-writers-vfs_mknod-try2 2006-06-16 15:58:09.000000000 -0700
    +++ lxc-dave/fs/namei.c 2006-06-16 15:58:09.000000000 -0700
    @@ -1857,14 +1857,26 @@ asmlinkage long sys_mknodat(int dfd, con
    if (!IS_ERR(dentry)) {
    switch (mode & S_IFMT) {
    case 0: case S_IFREG:
    + error = mnt_want_write(nd.mnt);
    + if (error)
    + break;
    error = vfs_create(nd.dentry->d_inode,dentry,mode,&nd);
    + mnt_drop_write(nd.mnt);
    break;
    case S_IFCHR: case S_IFBLK:
    + error = mnt_want_write(nd.mnt);
    + if (error)
    + break;
    error = vfs_mknod(nd.dentry->d_inode,dentry,mode,
    new_decode_dev(dev));
    + mnt_drop_write(nd.mnt);
    break;
    case S_IFIFO: case S_IFSOCK:
    + error = mnt_want_write(nd.mnt);
    + if (error)
    + break;
    error = vfs_mknod(nd.dentry->d_inode,dentry,mode,0);
    + mnt_drop_write(nd.mnt);
    break;
    case S_IFDIR:
    error = -EPERM;
    diff -puN fs/nfsd/vfs.c~C-elevate-writers-vfs_mknod-try2 fs/nfsd/vfs.c
    --- lxc/fs/nfsd/vfs.c~C-elevate-writers-vfs_mknod-try2 2006-06-16 15:58:09.000000000 -0700
    +++ lxc-dave/fs/nfsd/vfs.c 2006-06-16 15:58:09.000000000 -0700
    @@ -1153,6 +1153,9 @@ nfsd_create(struct svc_rqst *rqstp, stru
    /*
    * Get the dir op function pointer.
    */
    + err = mnt_want_write(fhp->fh_export->ex_mnt);
    + if (err)
    + goto out_nfserr;
    err = nfserr_perm;
    switch (type) {
    case S_IFREG:
    @@ -1171,6 +1174,7 @@ nfsd_create(struct svc_rqst *rqstp, stru
    printk("nfsd: bad file type %o in nfsd_create\n", type);
    err = -EINVAL;
    }
    + mnt_drop_write(fhp->fh_export->ex_mnt);
    if (err < 0)
    goto out_nfserr;

    diff -puN net/unix/af_unix.c~C-elevate-writers-vfs_mknod-try2 net/unix/af_unix.c
    --- lxc/net/unix/af_unix.c~C-elevate-writers-vfs_mknod-try2 2006-06-16 15:58:09.000000000 -0700
    +++ lxc-dave/net/unix/af_unix.c 2006-06-16 15:58:09.000000000 -0700
    @@ -789,7 +789,11 @@ static int unix_bind(struct socket *sock
    */
    mode = S_IFSOCK |
    (SOCK_INODE(sock)->i_mode & ~current->fs->umask);
    + err = mnt_want_write(nd.mnt);
    + if (err)
    + goto out_mknod_dput;
    err = vfs_mknod(nd.dentry->d_inode, dentry, mode, 0);
    + mnt_drop_write(nd.mnt);
    if (err)
    goto out_mknod_dput;
    mutex_unlock(&nd.dentry->d_inode->i_mutex);
    _
    -
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