diff mbox series

mm/shmem.c: Fix the missing unaccount on the failed path

Message ID 20200920163005.97079-1-tianjia.zhang@linux.alibaba.com
State New
Headers show
Series mm/shmem.c: Fix the missing unaccount on the failed path | expand

Commit Message

Tianjia Zhang Sept. 20, 2020, 4:30 p.m. UTC
In function __shmem_file_setup(), shmem_unacct_size() is forgotten
on the failed path, so add it.

Fixes: 93dec2da7b234 ("... and switch shmem_file_setup() to alloc_file_pseudo()")
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Tianjia Zhang <tianjia.zhang@linux.alibaba.com>
---
 mm/shmem.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

Comments

Hugh Dickins Sept. 20, 2020, 6:49 p.m. UTC | #1
On Mon, 21 Sep 2020, Tianjia Zhang wrote:

> In function __shmem_file_setup(), shmem_unacct_size() is forgotten
> on the failed path, so add it.
> 
> Fixes: 93dec2da7b234 ("... and switch shmem_file_setup() to alloc_file_pseudo()")
> Cc: Al Viro <viro@zeniv.linux.org.uk>
> Signed-off-by: Tianjia Zhang <tianjia.zhang@linux.alibaba.com>
> ---
>  mm/shmem.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/mm/shmem.c b/mm/shmem.c
> index 8e2b35ba93ad..591410dc3541 100644
> --- a/mm/shmem.c
> +++ b/mm/shmem.c
> @@ -4200,8 +4200,10 @@ static struct file *__shmem_file_setup(struct vfsmount *mnt, const char *name, l
>  	if (!IS_ERR(res))
>  		res = alloc_file_pseudo(inode, mnt, name, O_RDWR,
>  				&shmem_file_operations);
> -	if (IS_ERR(res))
> +	if (IS_ERR(res)) {
>  		iput(inode);
> +		shmem_unacct_size(flags, size);
> +	}
>  	return res;
>  }
>  
> -- 
> 2.19.1.3.ge56e4f7

Looks mistaken to me.

Is this something you noticed by source inspection,
or something you have observed in practice?

I haven't tried exercising this path while injecting errors into
alloc_file_pseudo(); but what I'd expect to happen is that the
iput(inode), which you see already on that error path, will get
to evict the inode, which will entail calling shmem_evict_inode(),
which does that shmem_unacct_size() itself.

Hugh
Tianjia Zhang Sept. 22, 2020, 5:27 a.m. UTC | #2
On 9/21/20 2:49 AM, Hugh Dickins wrote:
> On Mon, 21 Sep 2020, Tianjia Zhang wrote:
> 
>> In function __shmem_file_setup(), shmem_unacct_size() is forgotten
>> on the failed path, so add it.
>>
>> Fixes: 93dec2da7b234 ("... and switch shmem_file_setup() to alloc_file_pseudo()")
>> Cc: Al Viro <viro@zeniv.linux.org.uk>
>> Signed-off-by: Tianjia Zhang <tianjia.zhang@linux.alibaba.com>
>> ---
>>   mm/shmem.c | 4 +++-
>>   1 file changed, 3 insertions(+), 1 deletion(-)
>>
>> diff --git a/mm/shmem.c b/mm/shmem.c
>> index 8e2b35ba93ad..591410dc3541 100644
>> --- a/mm/shmem.c
>> +++ b/mm/shmem.c
>> @@ -4200,8 +4200,10 @@ static struct file *__shmem_file_setup(struct vfsmount *mnt, const char *name, l
>>   	if (!IS_ERR(res))
>>   		res = alloc_file_pseudo(inode, mnt, name, O_RDWR,
>>   				&shmem_file_operations);
>> -	if (IS_ERR(res))
>> +	if (IS_ERR(res)) {
>>   		iput(inode);
>> +		shmem_unacct_size(flags, size);
>> +	}
>>   	return res;
>>   }
>>   
>> -- 
>> 2.19.1.3.ge56e4f7
> 
> Looks mistaken to me.
> 
> Is this something you noticed by source inspection,
> or something you have observed in practice?
> 
> I haven't tried exercising this path while injecting errors into
> alloc_file_pseudo(); but what I'd expect to happen is that the
> iput(inode), which you see already on that error path, will get
> to evict the inode, which will entail calling shmem_evict_inode(),
> which does that shmem_unacct_size() itself.
> 
> Hugh
> 

I noticed by looking at the code. you are right, I neglected this point, 
thanks for your explanation.

Thanks,
Tianjia
diff mbox series

Patch

diff --git a/mm/shmem.c b/mm/shmem.c
index 8e2b35ba93ad..591410dc3541 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -4200,8 +4200,10 @@  static struct file *__shmem_file_setup(struct vfsmount *mnt, const char *name, l
 	if (!IS_ERR(res))
 		res = alloc_file_pseudo(inode, mnt, name, O_RDWR,
 				&shmem_file_operations);
-	if (IS_ERR(res))
+	if (IS_ERR(res)) {
 		iput(inode);
+		shmem_unacct_size(flags, size);
+	}
 	return res;
 }