linux-kernel - Re: [PATCH 1/3] shmem: fix double uncharge in __shmem_file

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Date:	Wed, 25 Jun 2014 20:44:28 -0700 (PDT)
From:	Hugh Dickins <hughd@...gle.com>
To:	Konstantin Khlebnikov <koct9i@...il.com>
cc:	linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
	Hugh Dickins <hughd@...gle.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] shmem: fix double uncharge in __shmem_file_setup()

On Wed, 25 Jun 2014, Konstantin Khlebnikov wrote:

> If __shmem_file_setup() fails on struct file allocation it uncharges memory
> commitment twice: first by shmem_unacct_size() and second time implicitly in
> shmem_evict_inode() when it kills newly created inode.
> This patch removes shmem_unacct_size() from error path if inode already here.
> 
> Signed-off-by: Konstantin Khlebnikov <koct9i@...il.com>

Acked-by: Hugh Dickins <hughd@...gle.com>

Thank you for the patch, and thank you for your patience (or perhaps for
your kindly concealed impatience): I realize that this (and the other two)
have been languishing in the must-get-to-look-at-it-sometime end of my
mailbox for nine months now - sorry.

> ---
>  mm/shmem.c |   12 ++++++------
>  1 file changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/mm/shmem.c b/mm/shmem.c
> index 8f419cf..0aabcbd 100644
> --- a/mm/shmem.c
> +++ b/mm/shmem.c
> @@ -2895,16 +2895,16 @@ static struct file *__shmem_file_setup(const char *name, loff_t size,
>  	this.len = strlen(name);
>  	this.hash = 0; /* will go */
>  	sb = shm_mnt->mnt_sb;
> +	path.mnt = mntget(shm_mnt);
>  	path.dentry = d_alloc_pseudo(sb, &this);
>  	if (!path.dentry)
>  		goto put_memory;
>  	d_set_d_op(path.dentry, &anon_ops);
> -	path.mnt = mntget(shm_mnt);
>  
>  	res = ERR_PTR(-ENOSPC);
>  	inode = shmem_get_inode(sb, NULL, S_IFREG | S_IRWXUGO, 0, flags);
>  	if (!inode)
> -		goto put_dentry;
> +		goto put_memory;
>  
>  	inode->i_flags |= i_flags;
>  	d_instantiate(path.dentry, inode);
> @@ -2912,19 +2912,19 @@ static struct file *__shmem_file_setup(const char *name, loff_t size,
>  	clear_nlink(inode);	/* It is unlinked */
>  	res = ERR_PTR(ramfs_nommu_expand_for_mapping(inode, size));
>  	if (IS_ERR(res))
> -		goto put_dentry;
> +		goto put_path;
>  
>  	res = alloc_file(&path, FMODE_WRITE | FMODE_READ,
>  		  &shmem_file_operations);
>  	if (IS_ERR(res))
> -		goto put_dentry;
> +		goto put_path;
>  
>  	return res;
>  
> -put_dentry:
> -	path_put(&path);
>  put_memory:
>  	shmem_unacct_size(flags, size);
> +put_path:
> +	path_put(&path);
>  	return res;
>  }
>  
--
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