On Thu, 5 Sep 2013, Chen Gang wrote:
> diff --git a/mm/shmem.c b/mm/shmem.c
> index f00c1c1..b4d44db 100644
> --- a/mm/shmem.c
> +++ b/mm/shmem.c
> @@ -883,16 +883,20 @@ redirty:
>
> #ifdef CONFIG_NUMA
> #ifdef CONFIG_TMPFS
> -static void shmem_show_mpol(struct seq_file *seq, struct mempolicy *mpol)
> +static int shmem_show_mpol(struct seq_file *seq, struct mempolicy *mpol)
> {
> char buffer[64];
> + int ret;
>
> if (!mpol || mpol->mode == MPOL_DEFAULT)
> - return; /* show nothing */
> + return 0; /* show nothing */
>
> - mpol_to_str(buffer, sizeof(buffer), mpol);
> + ret = mpol_to_str(buffer, sizeof(buffer), mpol);
I was wondering how mpol_to_str() could fail given a pointer to a stack
allocated buffer, so I checked and it happens if the mempolicy mode isn't
known or the buffer isn't long enough.
I think it would be better to keep mpol_to_str() returning void, and hence
avoiding the need for this patch, and make it so it cannot fail. If the
mode is invalid, just store a 0 to the buffer (or "unknown"); and if
maxlen isn't large enough, make it a compile-time error (let's avoid
trying to be fancy and allocating less than 64 bytes on the stack if a
given context is known to have short mempolicy strings).
> + if (ret < 0)
> + return ret;
>
> seq_printf(seq, ",mpol=%s", buffer);
> + return 0;
> }
>
> static struct mempolicy *shmem_get_sbmpol(struct shmem_sb_info *sbinfo)
> @@ -951,8 +955,9 @@ static struct page *shmem_alloc_page(gfp_t gfp,
> }
> #else /* !CONFIG_NUMA */
> #ifdef CONFIG_TMPFS
> -static inline void shmem_show_mpol(struct seq_file *seq, struct mempolicy *mpol)
> +static inline int shmem_show_mpol(struct seq_file *seq, struct mempolicy *mpol)
> {
> + return 0;
> }
> #endif /* CONFIG_TMPFS */
>
> @@ -2555,8 +2560,7 @@ static int shmem_show_options(struct seq_file *seq, struct dentry *root)
> if (!gid_eq(sbinfo->gid, GLOBAL_ROOT_GID))
> seq_printf(seq, ",gid=%u",
> from_kgid_munged(&init_user_ns, sbinfo->gid));
> - shmem_show_mpol(seq, sbinfo->mpol);
> - return 0;
> + return shmem_show_mpol(seq, sbinfo->mpol);
> }
> #endif /* CONFIG_TMPFS */
>
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