[CRIU] APPLIED[F/E]/cmnt: [SRU][UNSTABLE/BIONIC/XENIAL][PATCH] UBUNTU: SAUCE: overlayfs: use shiftfs hacks only with shiftfs as underlay

[Khaled Elmously]

Looks like this patch breaks the Eoan build:

/tmp/kernel-kmously-e9d4a02-jZGj/build/fs/overlayfs/file.c: In function 'ovl_open_realfile':
/tmp/kernel-kmously-e9d4a02-jZGj/build/fs/overlayfs/file.c:34:40: error: 'SHIFTFS_MAGIC' undeclared (first use in this function)
   34 |  if (realpath.dentry->d_sb->s_magic == SHIFTFS_MAGIC)
      |                                        ^~~~~~~~~~~~~
/tmp/kernel-kmously-e9d4a02-jZGj/build/fs/overlayfs/file.c:34:40: note: each undeclared identifier is reported only once for each function it appears in




I haven't tried building focal 




On 2020-04-24 15:28:40 , Kleber Souza wrote:
> On 23.04.20 12:11, Christian Brauner wrote:
> > From: Andrei Vagin <avagin at gmail.com>
> > 
> > BugLink: https://bugs.launchpad.net/bugs/1857257
> > 
> > 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
> > 
> > Cc: Stefan Bader <stefan.bader at canonical.com>
> > Cc: Connor Kuehl <connor.kuehl at canonical.com>
> > Cc: Kleber Sacilotto de Souza <kleber.souza at canonical.com>
> > Fixes: 58009298c6bd ("UBUNTU: SAUCE: overlayfs: allow with shiftfs as underlay")
> > Acked-by: Christian Brauner <christian.brauner at ubuntu.com>
> > Signed-off-by: Andrei Vagin <avagin at gmail.com>
> > ---
> >  fs/overlayfs/file.c | 9 ++++++---
> >  1 file changed, 6 insertions(+), 3 deletions(-)
> > 
> > diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c
> > index 4f94ef663569..9d16fff5342a 100644
> > --- a/fs/overlayfs/file.c
> > +++ b/fs/overlayfs/file.c
> > @@ -42,9 +42,12 @@ static struct file *ovl_open_realfile(const struct file *file,
> >  	int flags = file->f_flags | O_NOATIME | FMODE_NONOTIFY;
> >  
> >  	old_cred = ovl_override_creds(inode->i_sb);
> > -	ovl_path_real(file->f_path.dentry, &realpath);
> > -	realfile = open_with_fake_path(&realpath, flags, realinode,
> > -				       current_cred());
> > +	if (realpath.dentry->d_sb->s_magic == SHIFTFS_MAGIC)
> > +		realfile = open_with_fake_path(&realpath, flags, realinode,
> > +					       current_cred());
> > +	else
> > +		realfile = open_with_fake_path(&file->f_path, flags, realinode,
> > +					       current_cred());
> >  	revert_creds(old_cred);
> >  
> >  	pr_debug("open(%p[%pD2/%c], 0%o) -> (%p, 0%o)\n",
> > 
> > base-commit: 48f168950cd193d9beedc0afb0c79a254e32f637
> > 
> 
> According to the replies on the other shiftfs threads, I have applied this patch
> as well to all the stable series supporting shiftfs: eoan/linux and focal/linux.
> 
> Thanks,
> Kleber
> 
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