2022-03-23 14:06:33

by Xiaoke Wang

Subject: [PATCH] NFS: check the return value of mempool_alloc()

From: Xiaoke Wang <[email protected]>

The check was first removed in 518662e ("NFS: fix usage of mempools.")
as the passed GFP flags is `GFP_NOIO`.
While now the flag is changed to `GFP_KERNEL` by 2b17d72 ("NFS: Clean
up writeback code"), so it is better to check it.

Signed-off-by: Xiaoke Wang <[email protected]>
---
fs/nfs/write.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/fs/nfs/write.c b/fs/nfs/write.c
index eae9bf1..831fad9 100644
--- a/fs/nfs/write.c
+++ b/fs/nfs/write.c
@@ -106,8 +106,10 @@ static struct nfs_pgio_header *nfs_writehdr_alloc(void)
{
struct nfs_pgio_header *p = mempool_alloc(nfs_wdata_mempool, GFP_KERNEL);

- memset(p, 0, sizeof(*p));
- p->rw_mode = FMODE_WRITE;
+ if (p) {
+ memset(p, 0, sizeof(*p));
+ p->rw_mode = FMODE_WRITE;
+ }
return p;
}

--

2022-03-23 21:24:25

by NeilBrown

Subject: Re: [PATCH] NFS: check the return value of mempool_alloc()

On Wed, 23 Mar 2022, [email protected] wrote:
> From: Xiaoke Wang <[email protected]>
>
> The check was first removed in 518662e ("NFS: fix usage of mempools.")
> as the passed GFP flags is `GFP_NOIO`.
> While now the flag is changed to `GFP_KERNEL` by 2b17d72 ("NFS: Clean
> up writeback code"), so it is better to check it.

no. GFP_KERNEL is not that different from GFP_NOIO.

mempool_alloc() can only fail with __GFP_DIRECT_RECLAIM is not passed.

Please try to understand the code before you change it.

NeilBrown


>
> Signed-off-by: Xiaoke Wang <[email protected]>
> ---
> fs/nfs/write.c | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/fs/nfs/write.c b/fs/nfs/write.c
> index eae9bf1..831fad9 100644
> --- a/fs/nfs/write.c
> +++ b/fs/nfs/write.c
> @@ -106,8 +106,10 @@ static struct nfs_pgio_header *nfs_writehdr_alloc(void)
> {
> struct nfs_pgio_header *p = mempool_alloc(nfs_wdata_mempool, GFP_KERNEL);
>
> - memset(p, 0, sizeof(*p));
> - p->rw_mode = FMODE_WRITE;
> + if (p) {
> + memset(p, 0, sizeof(*p));
> + p->rw_mode = FMODE_WRITE;
> + }
> return p;
> }
>
> --
>
>