Re: [PATCH v2] tmpfs: allow decoding a file handle of an unlinked file

[Amir Goldstein <amir73il@gmail.com>]

On Sat, Jan 27, 2018 at 2:02 PM, Amir Goldstein <amir73il@gmail.com> wrote:
> On Fri, Jan 5, 2018 at 5:40 PM, Amir Goldstein <amir73il@gmail.com> wrote:
>> On Mon, Nov 13, 2017 at 8:43 AM, Amir Goldstein <amir73il@gmail.com> wrote:
>>> tmpfs uses the helper d_find_alias() to find a dentry from a decoded
>>> inode, but d_find_alias() skips unhashed dentries, so unlinked files
>>> cannot be decoded from a file handle.
>>>
>>> This can be reproduced using xfstests test program open_by_handle:
>>> $ open_by handle -c /tmp/testdir
>>> $ open_by_handle -dk /tmp/testdir
>>> open_by_handle(/tmp/testdir/file000000) returned 116 incorrectly on an
>>> unlinked open file!
>>>
>>> To fix this, if d_find_alias() can't find a hashed alias, call
>>> d_find_any_alias() to return an unhashed one.
>>>
>>> Cc: Hugh Dickins <hughd@google.com>
>>> Cc: Al Viro <viro@zeniv.linux.org.uk>
>>> Signed-off-by: Amir Goldstein <amir73il@gmail.com>
>>> ---
>>>
>>> Al, Miklos,
>>>
>>> Can either of you take this patch through your tree?
>>>
>>> Thanks,
>>> Amir.
>>>
>>> Changes since v1:
>>> - Prefer a hashed alias (James)
>>> - Use existing d_find_any_alias() helper
>>>
>>>  mm/shmem.c | 11 ++++++++++-
>>>  1 file changed, 10 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/mm/shmem.c b/mm/shmem.c
>>> index 07a1d22807be..5d3fa4099f54 100644
>>> --- a/mm/shmem.c
>>> +++ b/mm/shmem.c
>>> @@ -3404,6 +3404,15 @@ static int shmem_match(struct inode *ino, void *vfh)
>>>         return ino->i_ino == inum && fh[0] == ino->i_generation;
>>>  }
>>>
>>> +/* Find any alias of inode, but prefer a hashed alias */
>>> +static struct dentry *shmem_find_alias(struct inode *inode)
>>> +{
>>> +       struct dentry *alias = d_find_alias(inode);
>>> +
>>> +       return alias ?: d_find_any_alias(inode);
>>> +}
>>> +
>>> +
>>>  static struct dentry *shmem_fh_to_dentry(struct super_block *sb,
>>>                 struct fid *fid, int fh_len, int fh_type)
>>>  {
>>> @@ -3420,7 +3429,7 @@ static struct dentry *shmem_fh_to_dentry(struct super_block *sb,
>>>         inode = ilookup5(sb, (unsigned long)(inum + fid->raw[0]),
>>>                         shmem_match, fid->raw);
>>>         if (inode) {
>>> -               dentry = d_find_alias(inode);
>>> +               dentry = shmem_find_alias(inode);
>>>                 iput(inode);
>>>         }
>>>
>>> --
>>
>> Hugh,
>>
>> Did you get a chance to look at this patch?
>>
>> The test for decoding a file handle of an unlinked file has already been
>> merged to xfstest generic/467 and the test is failing on tmpfs without this
>> change.
>>
>> Can you please take or ACK this patch?
>>
>
> Ping.
>

Ping^2