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

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

[Amir Goldstein]

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);
 	}
 
-- 
2.7.4

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

[Amir Goldstein]

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?

Thanks,
Amir.

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

[Amir Goldstein]

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.

Real problem.

Trivial fix.

Al, Can you take this patch?

Thanks,
Amir.

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

[Amir Goldstein]

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