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    Subject[PATCH 08/17] VFS: Make more complete truncate operation available to CacheFiles
    Date
    Make a more complete truncate operation available to CacheFiles (including
    security checks and suchlike) so that it can use this to clear invalidated
    cache files.

    Signed-off-by: David Howells <dhowells@redhat.com>
    ---

    fs/open.c | 50 +++++++++++++++++++++++++++-----------------------
    include/linux/fs.h | 1 +
    2 files changed, 28 insertions(+), 23 deletions(-)

    diff --git a/fs/open.c b/fs/open.c
    index 77becc0..7535620 100644
    --- a/fs/open.c
    +++ b/fs/open.c
    @@ -61,33 +61,22 @@ int do_truncate(struct dentry *dentry, loff_t length, unsigned int time_attrs,
    return ret;
    }

    -static long do_sys_truncate(const char __user *pathname, loff_t length)
    +long vfs_truncate(struct path *path, loff_t length)
    {
    - struct path path;
    struct inode *inode;
    - int error;
    -
    - error = -EINVAL;
    - if (length < 0) /* sorry, but loff_t says... */
    - goto out;
    + long error;

    - error = user_path(pathname, &path);
    - if (error)
    - goto out;
    - inode = path.dentry->d_inode;
    + inode = path->dentry->d_inode;

    /* For directories it's -EISDIR, for other non-regulars - -EINVAL */
    - error = -EISDIR;
    if (S_ISDIR(inode->i_mode))
    - goto dput_and_out;
    -
    - error = -EINVAL;
    + return -EISDIR;
    if (!S_ISREG(inode->i_mode))
    - goto dput_and_out;
    + return -EINVAL;

    - error = mnt_want_write(path.mnt);
    + error = mnt_want_write(path->mnt);
    if (error)
    - goto dput_and_out;
    + goto out;

    error = inode_permission(inode, MAY_WRITE);
    if (error)
    @@ -111,19 +100,34 @@ static long do_sys_truncate(const char __user *pathname, loff_t length)

    error = locks_verify_truncate(inode, NULL, length);
    if (!error)
    - error = security_path_truncate(&path);
    + error = security_path_truncate(path);
    if (!error)
    - error = do_truncate(path.dentry, length, 0, NULL);
    + error = do_truncate(path->dentry, length, 0, NULL);

    put_write_and_out:
    put_write_access(inode);
    mnt_drop_write_and_out:
    - mnt_drop_write(path.mnt);
    -dput_and_out:
    - path_put(&path);
    + mnt_drop_write(path->mnt);
    out:
    return error;
    }
    +EXPORT_SYMBOL_GPL(vfs_truncate);
    +
    +static long do_sys_truncate(const char __user *pathname, loff_t length)
    +{
    + struct path path;
    + int error;
    +
    + if (length < 0) /* sorry, but loff_t says... */
    + return -EINVAL;
    +
    + error = user_path(pathname, &path);
    + if (!error) {
    + error = vfs_truncate(&path, length);
    + path_put(&path);
    + }
    + return error;
    +}

    SYSCALL_DEFINE2(truncate, const char __user *, path, long, length)
    {
    diff --git a/include/linux/fs.h b/include/linux/fs.h
    index 386da09..79449e4 100644
    --- a/include/linux/fs.h
    +++ b/include/linux/fs.h
    @@ -2014,6 +2014,7 @@ static inline int break_lease(struct inode *inode, unsigned int mode)

    /* fs/open.c */

    +extern long vfs_truncate(struct path *, loff_t);
    extern int do_truncate(struct dentry *, loff_t start, unsigned int time_attrs,
    struct file *filp);
    extern int do_fallocate(struct file *file, int mode, loff_t offset,


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