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    Subject[RFC][PATCH 09/27] elevate writer count for chown and friends
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    Date

    chown/chmod,etc... don't call permission in the same way
    that the normal "open for write" calls do. They still
    write to the filesystem, so bump the write count during
    these operations.

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

    lxc-dave/fs/open.c | 38 +++++++++++++++++++++++++++++++++-----
    1 files changed, 33 insertions(+), 5 deletions(-)

    diff -puN fs/open.c~C-elevate-writers-chown-and-friends fs/open.c
    --- lxc/fs/open.c~C-elevate-writers-chown-and-friends 2006-07-12 11:09:17.000000000 -0700
    +++ lxc-dave/fs/open.c 2006-07-12 11:09:26.000000000 -0700
    @@ -644,9 +644,12 @@ asmlinkage long sys_fchmod(unsigned int
    err = -EROFS;
    if (IS_RDONLY(inode))
    goto out_putf;
    + err = mnt_want_write(file->f_vfsmnt);
    + if (err)
    + goto out_putf;
    err = -EPERM;
    if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
    - goto out_putf;
    + goto out_drop_write;
    mutex_lock(&inode->i_mutex);
    if (mode == (mode_t) -1)
    mode = inode->i_mode;
    @@ -655,6 +658,8 @@ asmlinkage long sys_fchmod(unsigned int
    err = notify_change(dentry, &newattrs);
    mutex_unlock(&inode->i_mutex);

    +out_drop_write:
    + mnt_drop_write(file->f_vfsmnt);
    out_putf:
    fput(file);
    out:
    @@ -674,13 +679,16 @@ asmlinkage long sys_fchmodat(int dfd, co
    goto out;
    inode = nd.dentry->d_inode;

    + error = mnt_want_write(nd.mnt);
    + if (error)
    + goto dput_and_out;
    error = -EROFS;
    if (IS_RDONLY(inode))
    - goto dput_and_out;
    + goto out_drop_write;

    error = -EPERM;
    if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
    - goto dput_and_out;
    + goto out_drop_write;

    mutex_lock(&inode->i_mutex);
    if (mode == (mode_t) -1)
    @@ -690,6 +698,8 @@ asmlinkage long sys_fchmodat(int dfd, co
    error = notify_change(nd.dentry, &newattrs);
    mutex_unlock(&inode->i_mutex);

    +out_drop_write:
    + mnt_drop_write(nd.mnt);
    dput_and_out:
    path_release(&nd);
    out:
    @@ -715,7 +725,7 @@ static int chown_common(struct dentry *
    error = -EROFS;
    if (IS_RDONLY(inode))
    goto out;
    - error = -EPERM;
    + error = -EPERM;
    if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
    goto out;
    newattrs.ia_valid = ATTR_CTIME;
    @@ -744,7 +754,12 @@ asmlinkage long sys_chown(const char __u
    error = user_path_walk(filename, &nd);
    if (error)
    goto out;
    + error = mnt_want_write(nd.mnt);
    + if (error)
    + goto out_release;
    error = chown_common(nd.dentry, user, group);
    + mnt_drop_write(nd.mnt);
    +out_release:
    path_release(&nd);
    out:
    return error;
    @@ -764,7 +779,12 @@ asmlinkage long sys_fchownat(int dfd, co
    error = __user_walk_fd(dfd, filename, follow, &nd);
    if (error)
    goto out;
    + error = mnt_want_write(nd.mnt);
    + if (error)
    + goto out_release;
    error = chown_common(nd.dentry, user, group);
    + mnt_drop_write(nd.mnt);
    +out_release:
    path_release(&nd);
    out:
    return error;
    @@ -778,7 +798,11 @@ asmlinkage long sys_lchown(const char __
    error = user_path_walk_link(filename, &nd);
    if (error)
    goto out;
    + error = mnt_want_write(nd.mnt);
    + if (error)
    + goto out_release;
    error = chown_common(nd.dentry, user, group);
    +out_release:
    path_release(&nd);
    out:
    return error;
    @@ -794,10 +818,14 @@ asmlinkage long sys_fchown(unsigned int
    file = fget(fd);
    if (!file)
    goto out;
    -
    + error = mnt_want_write(file->f_vfsmnt);
    + if (error)
    + goto out_fput;
    dentry = file->f_dentry;
    audit_inode(NULL, dentry->d_inode);
    error = chown_common(dentry, user, group);
    + mnt_drop_write(file->f_vfsmnt);
    +out_fput:
    fput(file);
    out:
    return error;
    _
    -
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