Messages in this thread | ![/](/images/icornerl.gif) | | Date | Mon, 11 Dec 2023 11:43:06 -0800 | From | Andrew Morton <> | Subject | Re: [PATCH 1/2] fs/proc: show correct device and inode numbers in /proc/pid/maps |
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On Mon, 11 Dec 2023 11:30:47 -0800 Andrei Vagin <avagin@google.com> wrote:
> Device and inode numbers in /proc/pid/maps have to match numbers returned by > statx for the same files. > > /proc/pid/maps shows device and inode numbers of vma->vm_file-s. Here is > an issue. If a mapped file is on a stackable file system (e.g., > overlayfs), vma->vm_file is a backing file whose f_inode is on the > underlying filesystem. To show correct numbers, we need to get a user > file and shows its numbers. The same trick is used to show file paths in > /proc/pid/maps. > > But it isn't the end of this story. A file system can manipulate inode numbers > within the getattr callback (e.g., ovl_getattr), so vfs_getattr must be used to > get correct numbers.
Al, could you please comment on this?
Thanks.
> --- a/fs/proc/task_mmu.c > +++ b/fs/proc/task_mmu.c > @@ -273,9 +273,23 @@ show_map_vma(struct seq_file *m, struct vm_area_struct *vma) > const char *name = NULL; > > if (file) { > - struct inode *inode = file_inode(vma->vm_file); > - dev = inode->i_sb->s_dev; > - ino = inode->i_ino; > + const struct path *path; > + struct kstat stat; > + > + path = file_user_path(file); > + /* > + * A file system can manipulate inode numbers within the > + * getattr callback (e.g. ovl_getattr). > + */ > + if (!vfs_getattr_nosec(path, &stat, STATX_INO, AT_STATX_DONT_SYNC)) { > + dev = stat.dev; > + ino = stat.ino; > + } else { > + struct inode *inode = d_backing_inode(path->dentry); > + > + dev = inode->i_sb->s_dev; > + ino = inode->i_ino; > + } > pgoff = ((loff_t)vma->vm_pgoff) << PAGE_SHIFT; > } > > -- > 2.43.0.472.g3155946c3a-goog
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