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    Subject[RFC] fs, proc: Introduce the /proc/<pid>/map_files/ directory v2
    From: Pavel Emelyanov <xemul@parallels.com>

    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, the
    target is the file. Opening a symlink results in a file that point exactly
    to the same inode as them vma's one.

    This thing is aimed to help checkpointing processes.

    For example the ls -l of some arbitrary /proc/<pid>/map_files/

    | lr-x------ 1 cyrill cyrill 64 Aug 9 15:25 0x3d73a00000 -> /lib64/ld-2.5.so
    | lr-x------ 1 cyrill cyrill 64 Aug 9 15:25 0x3d73c1b000 -> /lib64/ld-2.5.so
    | lr-x------ 1 cyrill cyrill 64 Aug 9 15:25 0x3d73c1c000 -> /lib64/ld-2.5.so
    | lr-x------ 1 cyrill cyrill 64 Aug 9 15:25 0x3d73e00000 -> /lib64/libc-2.5.so
    | lr-x------ 1 cyrill cyrill 64 Aug 9 15:25 0x3d73f4e000 -> /lib64/libc-2.5.so

    v2:
    - /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

    Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
    Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
    ---
    fs/proc/base.c | 191 ++++++++++++++++++++++++++++++++++++++++++++++++
    include/linux/proc_fs.h | 5 +
    2 files changed, 195 insertions(+), 1 deletion(-)

    Please review. This is a part of previous c/r patchset as well
    but I guess it might be treated separately.

    Objections, complains, comments are highly appreciated!

    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
    @@ -2170,6 +2170,196 @@ static const struct file_operations proc
    .llseek = default_llseek,
    };

    +static const struct dentry_operations tid_map_files_dentry_operations = {
    + .d_revalidate = pid_revalidate,
    + .d_delete = pid_delete_dentry,
    +};
    +
    +static int proc_map_files_get_link(struct inode *inode, struct path *path)
    +{
    + struct task_struct *task;
    + struct vm_area_struct *vma;
    + struct mm_struct *mm;
    + unsigned long vm_start;
    + 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;
    +
    + vm_start = PROC_I(inode)->vm_start;
    +
    + down_read(&mm->mmap_sem);
    + vma = find_vma(mm, vm_start);
    + if (vma && vma->vm_start == vm_start && vma->vm_file) {
    + *path = vma->vm_file->f_path;
    + path_get(path);
    + rc = 0;
    + }
    + up_read(&mm->mmap_sem);
    +
    + mmput(mm);
    +
    +out:
    + return rc;
    +}
    +
    +static struct dentry *
    +proc_map_files_instantiate(struct inode *dir, struct dentry *dentry,
    + struct task_struct *task, const void *ptr)
    +{
    + const struct vm_area_struct *vma = ptr;
    + struct file *file = vma->vm_file;
    + 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->vm_start = vma->vm_start;
    + 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)
    +{
    + struct task_struct *task;
    + unsigned long vm_start;
    + struct vm_area_struct *vma;
    + struct mm_struct *mm;
    + struct dentry *result;
    + char *endp;
    +
    + result = ERR_PTR(-ENOENT);
    +
    + task = get_proc_task(dir);
    + if (!task)
    + goto out_no_task;
    +
    + vm_start = simple_strtoul(dentry->d_name.name, &endp, 16);
    + if (*endp != '\0')
    + goto out_no_mm;
    +
    + mm = get_task_mm(task);
    + if (!mm)
    + goto out_no_mm;
    +
    + down_read(&mm->mmap_sem);
    + vma = find_vma(mm, vm_start);
    + if (!vma || vma->vm_start != vm_start)
    + goto out_no_vma;
    + result = proc_map_files_instantiate(dir, dentry, task, vma);
    +
    +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:
    + mm = get_task_mm(task);
    + if (!mm)
    + goto out;
    + down_read(&mm->mmap_sem);
    + for (vma = mm->mmap, vmai = 2; vma; vma = vma->vm_next) {
    + char name[2 + 16 + 1];
    + int len;
    +
    + if (!vma->vm_file)
    + continue;
    +
    + vmai++;
    + if (vmai < filp->f_pos)
    + continue;
    +
    + filp->f_pos++;
    + len = snprintf(name, sizeof(name), "0x%lx", vma->vm_start);
    + if (proc_fill_cache(filp, dirent, filldir,
    + name, len, proc_map_files_instantiate,
    + task, vma) < 0)
    + break;
    + }
    + up_read(&mm->mmap_sem);
    + 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 +2975,7 @@ 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
    @@ -265,7 +265,10 @@ struct ctl_table;

    struct proc_inode {
    struct pid *pid;
    - int fd;
    + union {
    + int fd;
    + unsigned long vm_start;
    + };
    union proc_op op;
    struct proc_dir_entry *pde;
    struct ctl_table_header *sysctl;

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      Last update: 2011-08-24 10:55    [W:0.088 / U:0.176 seconds]
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