On Fri, Aug 26, 2011 at 03:29:44PM +0400, Cyrill Gorcunov wrote:
> On Thu, Aug 25, 2011 at 11:39:31PM +0200, Tejun Heo wrote:
> ...
> >
> > Why would you need an extra reference? All these data structures are
> > created dynamically on access and dentry is always available while any
> > operation on the inode is in progress so it's guaranteed to be
> > available and there's no reason to diddle with reference count.
> > Anyways, we can deal with this optimization later, I think.
> >
>
> Hi, thanks a huge for all feedback! Mind to give the below one a
> review shot? Hope this time I've addressed all concerns. Thanks.
> (please check map_files_d_revalidate() precisely). Complains are
> welcome, as always.
>
> Cyrill
> ---
> fs, proc: Introduce the /proc/<pid>/map_files/ directory v4
>
> This one behaves similarly to the /proc/<pid>/fd/ one - it contains symlinks
> one for each mapping with file, the name of a symlink is "vma->vm_start-vma->vm_end",
> the target is the file. Opening a symlink results in a file that point exactly
> to the same inode as them vma's one.
>
> For example the ls -l of some arbitrary /proc/<pid>/map_files/
>
> | lr-x------ 1 root root 64 Aug 26 06:40 7f8f80403000-7f8f80404000 -> /lib64/libc-2.5.so
> | lr-x------ 1 root root 64 Aug 26 06:40 7f8f8061e000-7f8f80620000 -> /lib64/libselinux.so.1
> | lr-x------ 1 root root 64 Aug 26 06:40 7f8f80826000-7f8f80827000 -> /lib64/libacl.so.1.1.0
> | lr-x------ 1 root root 64 Aug 26 06:40 7f8f80a2f000-7f8f80a30000 -> /lib64/librt-2.5.so
> | lr-x------ 1 root root 64 Aug 26 06:40 7f8f80a30000-7f8f80a4c000 -> /lib64/ld-2.5.so
>
> This helps checkpointing process in three ways:
>
> 1. When dumping a task mappings we do know exact file that is mapped by particular
> region. We do this by opening /proc/pid/map_files/address symlink the way we do
> with file descriptors.
>
> 2. This also helps in determining which anonymous shared mappings are shared with
> each other by comparing the inodes of them.
>
> 3. When restoring a set of process in case two of them has a mapping shared, we map
> the memory by the 1st one and then open its /proc/pid/map_files/address file and
> map it by the 2nd task.
>
> v2: (spotted by Tejun Heo)
> - /proc/<pid>/mfd changed to /proc/<pid>/map_files
> - find_vma helper is used instead of linear search
> - routines are re-grouped
> - d_revalidate is set now
>
> v3:
> - d_revalidate reworked, now it should drops no longer valid dentries (Tejun Heo)
> - ptrace_may_access added into proc_map_files_lookup (Vasiliy Kulikov)
> - because of filldir (which eventually might need to lock mmap_sem)
> the proc_map_files_readdir() was reworked to call proc_fill_cache()
> with unlocked mmap_sem
>
> v4: (feedback by Tejun Heo and Vasiliy Kulikov)
> - instead of saving data in proc_inode we rather make a dentry name
> to keep both vm_start and vm_end accordingly
> - d_revalidate now honor task credentials
>
> Signed-off-by: Pavel Emelyanov <xemul@xxxxxxxxxxxxx>
> Signed-off-by: Cyrill Gorcunov <gorcunov@xxxxxxxxxx>
> CC: Tejun Heo <tj@xxxxxxxxxx>
> CC: Vasiliy Kulikov <segoon@xxxxxxxxxxxx>
> ---
> fs/proc/base.c | 326 +++++++++++++++++++++++++++++++++++++++++++++++-
> include/linux/proc_fs.h | 2
> 2 files changed, 321 insertions(+), 7 deletions(-)
>
> Index: linux-2.6.git/fs/proc/base.c
> ===================================================================
> --- linux-2.6.git.orig/fs/proc/base.c
> +++ linux-2.6.git/fs/proc/base.c
> @@ -165,7 +165,7 @@ static int get_task_root(struct task_str
> return result;
> }
>
> -static int proc_cwd_link(struct inode *inode, struct path *path)
> +static int proc_cwd_link(struct dentry *dentry, struct inode *inode, struct path *path)
Put proc_get_link() change in separate patch?
> {
> struct task_struct *task = get_proc_task(inode);
> int result = -ENOENT;
> @@ -182,7 +182,7 @@ static int proc_cwd_link(struct inode *i
> return result;
> }
>
> -static int proc_root_link(struct inode *inode, struct path *path)
> +static int proc_root_link(struct dentry *dentry, struct inode *inode, struct path *path)
> {
> struct task_struct *task = get_proc_task(inode);
> int result = -ENOENT;
> @@ -1580,7 +1580,7 @@ static const struct file_operations proc
> .release = single_release,
> };
>
> -static int proc_exe_link(struct inode *inode, struct path *exe_path)
> +static int proc_exe_link(struct dentry *dentry, struct inode *inode, struct path *exe_path)
> {
> struct task_struct *task;
> struct mm_struct *mm;
> @@ -1616,7 +1616,7 @@ static void *proc_pid_follow_link(struct
> if (!proc_fd_access_allowed(inode))
> goto out;
>
> - error = PROC_I(inode)->op.proc_get_link(inode, &nd->path);
> + error = PROC_I(inode)->op.proc_get_link(dentry, inode, &nd->path);
> out:
> return ERR_PTR(error);
> }
> @@ -1655,7 +1655,7 @@ static int proc_pid_readlink(struct dent
> if (!proc_fd_access_allowed(inode))
> goto out;
>
> - error = PROC_I(inode)->op.proc_get_link(inode, &path);
> + error = PROC_I(inode)->op.proc_get_link(dentry, inode, &path);
> if (error)
> goto out;
>
> @@ -1947,7 +1947,7 @@ static int proc_fd_info(struct inode *in
> return -ENOENT;
> }
>
> -static int proc_fd_link(struct inode *inode, struct path *path)
> +static int proc_fd_link(struct dentry *dentry, struct inode *inode, struct path *path)
> {
> return proc_fd_info(inode, path, NULL);
> }
> @@ -2170,6 +2170,319 @@ static const struct file_operations proc
> .llseek = default_llseek,
> };
>
> +static struct vm_area_struct *
> +find_exact_vma(struct mm_struct *mm, unsigned long vm_start, unsigned long vm_end)
> +{
> + struct vm_area_struct *vma = find_vma(mm, vm_start);
> + if (vma && (vma->vm_start != vm_start || vma->vm_end != vm_end))
> + vma = NULL;
> + return vma;
> +}
> +
> +static int map_name_to_addr(const unsigned char *name, unsigned long *start, unsigned long *end)
> +{
> + int ret = -1;
> + char *endp;
> +
> + if (unlikely(!name))
> + goto err;
> +
> + *start = simple_strtoul(name, &endp, 16);
> + if (*endp != '-')
> + goto err;
> + *end = simple_strtoul(endp + 1, &endp, 16);
> + if (*endp != 0)
> + goto err;
> +
> + ret = 0;
> +
> +err:
> + return ret;
> +}
> +
> +static int map_files_d_revalidate(struct dentry *dentry, struct nameidata *nd)
> +{
> + struct vm_area_struct *vma = NULL;
> + unsigned long vm_start, vm_end;
> + struct task_struct *task;
> + const struct cred *cred;
> + struct mm_struct *mm;
> + struct inode *inode;
> +
> + if (nd && nd->flags & LOOKUP_RCU)
> + return -ECHILD;
> +
> + inode = dentry->d_inode;
> + task = get_proc_task(inode);
> + if (!task)
> + goto out;
> +
> + mm = get_task_mm(task);
> + put_task_struct(task);
> + if (!mm)
> + goto out;
> +
> + if (!map_name_to_addr(dentry->d_name.name, &vm_start, &vm_end)) {
> + down_read(&mm->mmap_sem);
> + vma = find_exact_vma(mm, vm_start, vm_end);
> + up_read(&mm->mmap_sem);
> + }
> +
> + mmput(mm);
> +
> + if (vma) {
> + if (task_dumpable(task)) {
> + rcu_read_lock();
> + cred = __task_cred(task);
> + inode->i_uid = cred->euid;
> + inode->i_gid = cred->egid;
> + rcu_read_unlock();
> + } else {
> + inode->i_uid = 0;
> + inode->i_gid = 0;
> + }
> + security_task_to_inode(task, inode);
> + return 1;
> + }
> +out:
> + d_drop(dentry);
> + return 0;
> +}
> +
> +static const struct dentry_operations tid_map_files_dentry_operations = {
> + .d_revalidate = map_files_d_revalidate,
> + .d_delete = pid_delete_dentry,
> +};
> +
> +static int proc_map_files_get_link(struct dentry *dentry, struct inode *inode, struct path *path)
> +{
> + unsigned long vm_start, vm_end;
> + struct vm_area_struct *vma;
> + struct task_struct *task;
> + struct mm_struct *mm;
> + int rc = -ENOENT;
> +
> + task = get_proc_task(inode);
> + if (!task)
> + goto out;
> +
> + mm = get_task_mm(task);
> + put_task_struct(task);
> + if (!mm)
> + goto out;
> +
> + if (map_name_to_addr(dentry->d_name.name,
> + &vm_start, &vm_end))
> + goto out_mmput;
> +
> + down_read(&mm->mmap_sem);
> + vma = find_exact_vma(mm, vm_start, vm_end);
> + if (vma && vma->vm_file) {
> + *path = vma->vm_file->f_path;
> + path_get(path);
> + rc = 0;
> + }
> + up_read(&mm->mmap_sem);
> +
> +out_mmput:
> + mmput(mm);
> +out:
> + return rc;
> +}
> +
> +struct map_files_info {
> + struct file *file;
> + unsigned char name[16+16+2]; /* max: %016lx-%016lx\0 */
> + unsigned long len;
> +};
> +
> +static struct dentry *
> +proc_map_files_instantiate(struct inode *dir, struct dentry *dentry,
> + struct task_struct *task, const void *ptr)
> +{
> + const struct file *file = ptr;
> + struct proc_inode *ei;
> + struct inode *inode;
> +
> + if (!file)
> + return ERR_PTR(-ENOENT);
> +
> + inode = proc_pid_make_inode(dir->i_sb, task);
> + if (!inode)
> + return ERR_PTR(-ENOENT);
> +
> + ei = PROC_I(inode);
> + ei->op.proc_get_link = proc_map_files_get_link;
> +
> + inode->i_op = &proc_pid_link_inode_operations;
> + inode->i_size = 64;
> + inode->i_mode = S_IFLNK;
> +
> + if (file->f_mode & FMODE_READ)
> + inode->i_mode |= S_IRUSR | S_IXUSR;
> + if (file->f_mode & FMODE_WRITE)
> + inode->i_mode |= S_IWUSR | S_IXUSR;
> +
> + d_set_d_op(dentry, &tid_map_files_dentry_operations);
> + d_add(dentry, inode);
> +
> + return NULL;
> +}
> +
> +static struct dentry *proc_map_files_lookup(struct inode *dir,
> + struct dentry *dentry, struct nameidata *nd)
> +{
> + unsigned long vm_start, vm_end;
> + struct task_struct *task;
> + struct vm_area_struct *vma;
> + struct mm_struct *mm;
> + struct dentry *result;
> +
> + result = ERR_PTR(-ENOENT);
> + task = get_proc_task(dir);
> + if (!task)
> + goto out_no_task;
> +
> + result = ERR_PTR(-EPERM);
> + if (!ptrace_may_access(task, PTRACE_MODE_READ));
> + goto out_no_mm;
> +
> + result = ERR_PTR(-ENOENT);
> + if (map_name_to_addr(dentry->d_name.name,
> + &vm_start, &vm_end))
> + goto out_no_mm;
> +
> + mm = get_task_mm(task);
> + if (!mm)
> + goto out_no_mm;
> +
> + down_read(&mm->mmap_sem);
> + vma = find_exact_vma(mm, vm_start, vm_end);
> + if (!vma)
> + goto out_no_vma;
> +
> + result = proc_map_files_instantiate(dir, dentry, task, vma->vm_file);
> +
> +out_no_vma:
> + up_read(&mm->mmap_sem);
> + mmput(mm);
> +out_no_mm:
> + put_task_struct(task);
> +out_no_task:
> + return result;
> +}
> +
> +static const struct inode_operations proc_map_files_inode_operations = {
> + .lookup = proc_map_files_lookup,
> + .setattr = proc_setattr,
> +};
> +
> +static int proc_map_files_readdir(struct file *filp, void *dirent, filldir_t filldir)
> +{
> + struct dentry *dentry = filp->f_path.dentry;
> + struct inode *inode = dentry->d_inode;
> + struct vm_area_struct *vma;
> + struct task_struct *task;
> + struct mm_struct *mm;
> + unsigned int vmai;
> + ino_t ino;
> + int ret;
> +
> + ret = -ENOENT;
> + task = get_proc_task(inode);
> + if (!task)
> + goto out_no_task;
> +
> + ret = -EPERM;
> + if (!ptrace_may_access(task, PTRACE_MODE_READ))
> + goto out;
> +
> + ret = 0;
> + switch (filp->f_pos) {
> + case 0:
> + ino = inode->i_ino;
> + if (filldir(dirent, ".", 1, 0, ino, DT_DIR) < 0)
> + goto out;
> + filp->f_pos++;
> + case 1:
> + ino = parent_ino(dentry);
> + if (filldir(dirent, "..", 2, 1, ino, DT_DIR) < 0)
> + goto out;
> + filp->f_pos++;
> + default:
> + {
> + unsigned long nr_files, used, i;
> + struct map_files_info *info;
> +
> + mm = get_task_mm(task);
> + if (!mm)
> + goto out;
> + down_read(&mm->mmap_sem);
> +
> + nr_files = 0;
> + for (vma = mm->mmap; vma; vma = vma->vm_next) {
> + if (vma->vm_file)
> + nr_files++;
> + }
> + if (!nr_files)
> + goto out;
up_read(&mm->mmap_sem); ?
> +
> + info = kmalloc(nr_files * sizeof(*info), GFP_KERNEL);
> + if (!info) {
> + ret = -ENOMEM;
> + goto out;
Ditto.
> + }
> +
> + used = 0;
> + for (vma = mm->mmap, vmai = 2; vma; vma = vma->vm_next) {
> + if (!vma->vm_file)
> + continue;
> + vmai++;
> + if (vmai <= filp->f_pos)
> + continue;
> +
> + get_file(vma->vm_file);
> + info[used].file = vma->vm_file;
> + info[used].len = snprintf(info[used].name,
> + sizeof(info[used].name),
> + "%lx-%lx", vma->vm_start,
> + vma->vm_end);
> + used++;
> + }
> +
> + up_read(&mm->mmap_sem);
> +
> + for (i = 0; i < used; i++) {
> + ret = proc_fill_cache(filp, dirent, filldir,
> + info[i].name,
> + info[i].len,
> + proc_map_files_instantiate,
> + task, info[i].file);
> + if (ret)
> + break;
> + filp->f_pos++;
> + }
> +
> + for (i = 0; i < used; i++)
> + put_filp(info[i].file);
> +
> + kfree(info);
> + mmput(mm);
> + }
> + }
> +
> +out:
> + put_task_struct(task);
> +out_no_task:
> + return ret;
> +}
> +
> +static const struct file_operations proc_map_files_operations = {
> + .read = generic_read_dir,
> + .readdir = proc_map_files_readdir,
> + .llseek = default_llseek,
> +};
> +
> /*
> * /proc/pid/fd needs a special permission handler so that a process can still
> * access /proc/self/fd after it has executed a setuid().
> @@ -2785,6 +3098,7 @@ static const struct inode_operations pro
> static const struct pid_entry tgid_base_stuff[] = {
> DIR("task", S_IRUGO|S_IXUGO, proc_task_inode_operations, proc_task_operations),
> DIR("fd", S_IRUSR|S_IXUSR, proc_fd_inode_operations, proc_fd_operations),
> + DIR("map_files", S_IRUSR|S_IXUSR, proc_map_files_inode_operations, proc_map_files_operations),
> DIR("fdinfo", S_IRUSR|S_IXUSR, proc_fdinfo_inode_operations, proc_fdinfo_operations),
> DIR("ns", S_IRUSR|S_IXUGO, proc_ns_dir_inode_operations, proc_ns_dir_operations),
> #ifdef CONFIG_NET
> Index: linux-2.6.git/include/linux/proc_fs.h
> ===================================================================
> --- linux-2.6.git.orig/include/linux/proc_fs.h
> +++ linux-2.6.git/include/linux/proc_fs.h
> @@ -253,7 +253,7 @@ extern const struct proc_ns_operations u
> extern const struct proc_ns_operations ipcns_operations;
>
> union proc_op {
> - int (*proc_get_link)(struct inode *, struct path *);
> + int (*proc_get_link)(struct dentry *, struct inode *, struct path *);
> int (*proc_read)(struct task_struct *task, char *page);
> int (*proc_show)(struct seq_file *m,
> struct pid_namespace *ns, struct pid *pid,
> _______________________________________________
> Containers mailing list
> Containers@xxxxxxxxxxxxxxxxxxxxxxxxxx
> https://lists.linux-foundation.org/mailman/listinfo/containers
--
Kirill A. Shutemov
--
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