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

[Kleber Souza]

On 27.04.20 01:02, Khaled Elmously wrote:
> 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

Christian,

This seems to fix it:

diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c
index 30f35c53ce04..a2faa086ee4b 100644
--- a/fs/overlayfs/file.c
+++ b/fs/overlayfs/file.c
@@ -3,6 +3,7 @@
  * Copyright (C) 2017 Red Hat, Inc.
  */
 
+#include <uapi/linux/magic.h>
 #include <linux/cred.h>
 #include <linux/file.h>
 #include <linux/mount.h>


Would you agree in me amending your patch to fix it?


Kleber


> 
> 
> 
> 
> 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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