@@ -490,6 +490,32 @@ static int ovl_fsync(struct file *file, loff_t start, loff_t end, int datasync)
return ret;
}
+/*
+ * In map_files_get_link() (fs/proc/base.c)
+ * we need to determine correct path from overlayfs.
+ * But real_mount(realfile->f_path.mnt) may be not
+ * equal to real_mount(file->f_path.mnt). In such case
+ * fdinfo of the same file which was opened from
+ * /proc/<pid>/map_files/... and "usual" path
+ * will show different mnt_id.
+ *
+ * We solve issue like in aufs by using additional
+ * field on struct vm_area_struct called "vm_prfile"
+ * which is used only for fdinfo/"printing" needs.
+ *
+ * See also mm/prfile.c
+ */
+static void ovl_vm_prfile_set(struct vm_area_struct *vma,
+ struct file *file)
+{
+ get_file(file);
+ vma->vm_prfile = file;
+#ifndef CONFIG_MMU
+ get_file(file);
+ vma->vm_region->vm_prfile = file;
+#endif
+}
+
static int ovl_mmap(struct file *file, struct vm_area_struct *vma)
{
struct file *realfile = file->private_data;
@@ -507,6 +533,10 @@ static int ovl_mmap(struct file *file, struct vm_area_struct *vma)
old_cred = ovl_override_creds(file_inode(file)->i_sb);
ret = call_mmap(vma->vm_file, vma);
revert_creds(old_cred);
+
+ if (!ret)
+ ovl_vm_prfile_set(vma, file);
+
ovl_file_accessed(file);
return ret;
BugLink: https://bugs.launchpad.net/bugs/1967924 BugLink: https://bugs.launchpad.net/bugs/1857257 BugLink: https://bugs.launchpad.net/bugs/1967924 The hack was introduced in ("UBUNTU: SAUCE: overlayfs: allow with shiftfs as underlay") and it broke checkpoint/restore of docker contains: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1857257 The following script can be used to trigger the issue: #!/bin/bash cat > test.py << EOF import sys f = open("/proc/self/maps") for l in f.readlines(): if "python" not in l: continue print(l) s = l.split() start, end = s[0].split("-") fname = s[-1] print(start, end, fname) break else: sys.exit(1) test_file1 = open(fname) test_file2 = open("/proc/self/map_files/%s-%s" % (start, end)) fdinfo1 = open("/proc/self/fdinfo/%d" % test_file1.fileno()).read() fdinfo2 = open("/proc/self/fdinfo/%d" % test_file2.fileno()).read() if fdinfo1 != fdinfo2: print("FAIL") print(test_file1) print(fdinfo1) print(test_file2) print(fdinfo2) sys.exit(1) print("PASS") EOF sudo docker run -it --privileged --rm -v `pwd`:/mnt python python /mnt/test.py Thanks to Andrei Vagin for the reproducer and investigation of this problem. Cc: Andrei Vagin <avagin@gmail.com> Cc: Adrian Reber <areber@redhat.com> Cc: Christian Brauner <christian@brauner.io> Cc: Stefan Bader <stefan.bader@canonical.com> Cc: Kleber Sacilotto de Souza <kleber.souza@canonical.com> Cc: Andrea Righi <andrea.righi@canonical.com> Depends-on: cc51ba77abaa ("UBUNTU: SAUCE: for aufs mmap: print the virtual file path") Fixes: a80dceb9e85 ("UBUNTU: SAUCE: overlayfs: allow with shiftfs as underlay") Signed-off-by: Alexander Mikhalitsyn <alexander.mikhalitsyn@virtuozzo.com> --- fs/overlayfs/file.c | 30 ++++++++++++++++++++++++++++++ 1 file changed, 30 insertions(+)