[PATCH] ceph: check folio PG_private bit instead of folio->private

[PATCH] ceph: check folio PG_private bit instead of folio->private

[Xiubo Li]

The pages in the file mapping maybe reclaimed and reused by other
subsystems and the page->private maybe used as flags field or
something else, if later that pages are used by page caches again
the page->private maybe not cleared as expected.

Here will check the PG_private bit instead of the folio->private.

Cc: stable@vger.kernel.org
URL: https://tracker.ceph.com/issues/55421
Signed-off-by: Xiubo Li <xiubli@redhat.com>
---
 fs/ceph/addr.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/fs/ceph/addr.c b/fs/ceph/addr.c
index 63b7430e1ce6..1a108f24e7d9 100644
--- a/fs/ceph/addr.c
+++ b/fs/ceph/addr.c
@@ -85,7 +85,7 @@ static bool ceph_dirty_folio(struct address_space *mapping, struct folio *folio)
 	if (folio_test_dirty(folio)) {
 		dout("%p dirty_folio %p idx %lu -- already dirty\n",
 		     mapping->host, folio, folio->index);
-		VM_BUG_ON_FOLIO(!folio_get_private(folio), folio);
+		VM_BUG_ON_FOLIO(!folio_test_private(folio), folio);
 		return false;
 	}
 
@@ -122,7 +122,7 @@ static bool ceph_dirty_folio(struct address_space *mapping, struct folio *folio)
 	 * Reference snap context in folio->private.  Also set
 	 * PagePrivate so that we get invalidate_folio callback.
 	 */
-	VM_BUG_ON_FOLIO(folio_get_private(folio), folio);
+	VM_BUG_ON_FOLIO(folio_test_private(folio), folio);
 	folio_attach_private(folio, snapc);
 
 	return ceph_fscache_dirty_folio(mapping, folio);
@@ -150,7 +150,7 @@ static void ceph_invalidate_folio(struct folio *folio, size_t offset,
 	}
 
 	WARN_ON(!folio_test_locked(folio));
-	if (folio_get_private(folio)) {
+	if (folio_test_private(folio)) {
 		dout("%p invalidate_folio idx %lu full dirty page\n",
 		     inode, folio->index);
 
-- 
2.36.0.rc1

Re: [PATCH] ceph: check folio PG_private bit instead of folio->private

[Jeff Layton]

On Sun, 2022-05-08 at 14:15 +0800, Xiubo Li wrote:
> The pages in the file mapping maybe reclaimed and reused by other
> subsystems and the page->private maybe used as flags field or
> something else, if later that pages are used by page caches again
> the page->private maybe not cleared as expected.
> 
> Here will check the PG_private bit instead of the folio->private.
> 
> Cc: stable@vger.kernel.org
> URL: https://tracker.ceph.com/issues/55421
> Signed-off-by: Xiubo Li <xiubli@redhat.com>
> ---
>  fs/ceph/addr.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/ceph/addr.c b/fs/ceph/addr.c
> index 63b7430e1ce6..1a108f24e7d9 100644
> --- a/fs/ceph/addr.c
> +++ b/fs/ceph/addr.c
> @@ -85,7 +85,7 @@ static bool ceph_dirty_folio(struct address_space *mapping, struct folio *folio)
>  	if (folio_test_dirty(folio)) {
>  		dout("%p dirty_folio %p idx %lu -- already dirty\n",
>  		     mapping->host, folio, folio->index);
> -		VM_BUG_ON_FOLIO(!folio_get_private(folio), folio);
> +		VM_BUG_ON_FOLIO(!folio_test_private(folio), folio);
>  		return false;
>  	}
>  
> @@ -122,7 +122,7 @@ static bool ceph_dirty_folio(struct address_space *mapping, struct folio *folio)
>  	 * Reference snap context in folio->private.  Also set
>  	 * PagePrivate so that we get invalidate_folio callback.
>  	 */
> -	VM_BUG_ON_FOLIO(folio_get_private(folio), folio);
> +	VM_BUG_ON_FOLIO(folio_test_private(folio), folio);
>  	folio_attach_private(folio, snapc);
>  
>  	return ceph_fscache_dirty_folio(mapping, folio);
> @@ -150,7 +150,7 @@ static void ceph_invalidate_folio(struct folio *folio, size_t offset,
>  	}
>  
>  	WARN_ON(!folio_test_locked(folio));
> -	if (folio_get_private(folio)) {
> +	if (folio_test_private(folio)) {
>  		dout("%p invalidate_folio idx %lu full dirty page\n",
>  		     inode, folio->index);
>  

Reviewed-by: Jeff Layton <jlayton@kernel.org>

Re: [PATCH] ceph: check folio PG_private bit instead of folio->private

[Luís Henriques]

On Sun, May 08, 2022 at 02:15:43PM +0800, Xiubo Li wrote:
> The pages in the file mapping maybe reclaimed and reused by other
> subsystems and the page->private maybe used as flags field or
> something else, if later that pages are used by page caches again
> the page->private maybe not cleared as expected.
> 
> Here will check the PG_private bit instead of the folio->private.

I thought that a patch to set ->private to NULL in the folio code (maybe
in folio_end_private_2()) would make sense.  But then... it probably
wouldn't get accepted as we're probably not supposed to assume these
fields are initialised.

Anyway, thanks Xiubo!

Reviewed-by: Luís Henriques <lhenriques@suse.de>

Cheers,
--
Luís

> 
> Cc: stable@vger.kernel.org
> URL: https://tracker.ceph.com/issues/55421
> Signed-off-by: Xiubo Li <xiubli@redhat.com>
> ---
>  fs/ceph/addr.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/ceph/addr.c b/fs/ceph/addr.c
> index 63b7430e1ce6..1a108f24e7d9 100644
> --- a/fs/ceph/addr.c
> +++ b/fs/ceph/addr.c
> @@ -85,7 +85,7 @@ static bool ceph_dirty_folio(struct address_space *mapping, struct folio *folio)
>  	if (folio_test_dirty(folio)) {
>  		dout("%p dirty_folio %p idx %lu -- already dirty\n",
>  		     mapping->host, folio, folio->index);
> -		VM_BUG_ON_FOLIO(!folio_get_private(folio), folio);
> +		VM_BUG_ON_FOLIO(!folio_test_private(folio), folio);
>  		return false;
>  	}
>  
> @@ -122,7 +122,7 @@ static bool ceph_dirty_folio(struct address_space *mapping, struct folio *folio)
>  	 * Reference snap context in folio->private.  Also set
>  	 * PagePrivate so that we get invalidate_folio callback.
>  	 */
> -	VM_BUG_ON_FOLIO(folio_get_private(folio), folio);
> +	VM_BUG_ON_FOLIO(folio_test_private(folio), folio);
>  	folio_attach_private(folio, snapc);
>  
>  	return ceph_fscache_dirty_folio(mapping, folio);
> @@ -150,7 +150,7 @@ static void ceph_invalidate_folio(struct folio *folio, size_t offset,
>  	}
>  
>  	WARN_ON(!folio_test_locked(folio));
> -	if (folio_get_private(folio)) {
> +	if (folio_test_private(folio)) {
>  		dout("%p invalidate_folio idx %lu full dirty page\n",
>  		     inode, folio->index);
>  
> -- 
> 2.36.0.rc1
> 

Re: [PATCH] ceph: check folio PG_private bit instead of folio->private

[Xiubo Li]

On 5/9/22 5:13 PM, Luís Henriques wrote:
> On Sun, May 08, 2022 at 02:15:43PM +0800, Xiubo Li wrote:
>> The pages in the file mapping maybe reclaimed and reused by other
>> subsystems and the page->private maybe used as flags field or
>> something else, if later that pages are used by page caches again
>> the page->private maybe not cleared as expected.
>>
>> Here will check the PG_private bit instead of the folio->private.
> I thought that a patch to set ->private to NULL in the folio code (maybe
> in folio_end_private_2()) would make sense.  But then... it probably
> wouldn't get accepted as we're probably not supposed to assume these
> fields are initialised.

Not very sure this or something like this is correct place to clear the 
->private.

Because the 'folio' and 'page' struct are like union and also in the 
'page' struct there also has a big union, such as any of the following 
field could affect the ->private:


unsigned long private;
unsigned long dma_addr_upper;
atomic_long_t pp_frag_count;
atomic_t compound_pincount;
spinlock_t ptl;


> Anyway, thanks Xiubo!
>
> Reviewed-by: Luís Henriques <lhenriques@suse.de>

Thanks Luis.

-- Xiubo


> Cheers,
> --
> Luís
>
>> Cc: stable@vger.kernel.org
>> URL: https://tracker.ceph.com/issues/55421
>> Signed-off-by: Xiubo Li <xiubli@redhat.com>
>> ---
>>   fs/ceph/addr.c | 6 +++---
>>   1 file changed, 3 insertions(+), 3 deletions(-)
>>
>> diff --git a/fs/ceph/addr.c b/fs/ceph/addr.c
>> index 63b7430e1ce6..1a108f24e7d9 100644
>> --- a/fs/ceph/addr.c
>> +++ b/fs/ceph/addr.c
>> @@ -85,7 +85,7 @@ static bool ceph_dirty_folio(struct address_space *mapping, struct folio *folio)
>>   	if (folio_test_dirty(folio)) {
>>   		dout("%p dirty_folio %p idx %lu -- already dirty\n",
>>   		     mapping->host, folio, folio->index);
>> -		VM_BUG_ON_FOLIO(!folio_get_private(folio), folio);
>> +		VM_BUG_ON_FOLIO(!folio_test_private(folio), folio);
>>   		return false;
>>   	}
>>   
>> @@ -122,7 +122,7 @@ static bool ceph_dirty_folio(struct address_space *mapping, struct folio *folio)
>>   	 * Reference snap context in folio->private.  Also set
>>   	 * PagePrivate so that we get invalidate_folio callback.
>>   	 */
>> -	VM_BUG_ON_FOLIO(folio_get_private(folio), folio);
>> +	VM_BUG_ON_FOLIO(folio_test_private(folio), folio);
>>   	folio_attach_private(folio, snapc);
>>   
>>   	return ceph_fscache_dirty_folio(mapping, folio);
>> @@ -150,7 +150,7 @@ static void ceph_invalidate_folio(struct folio *folio, size_t offset,
>>   	}
>>   
>>   	WARN_ON(!folio_test_locked(folio));
>> -	if (folio_get_private(folio)) {
>> +	if (folio_test_private(folio)) {
>>   		dout("%p invalidate_folio idx %lu full dirty page\n",
>>   		     inode, folio->index);
>>   
>> -- 
>> 2.36.0.rc1
>>