On 03/24/2015 06:08 PM, David Rientjes wrote:
> Mempools based on slab caches with object constructors are risky because
> element allocation can happen either from the slab cache itself, meaning
> the constructor is properly called before returning, or from the mempool
> reserve pool, meaning the constructor is not called before returning,
> depending on the allocation context.
>
> For this reason, we should disallow creating mempools based on slab
> caches that have object constructors. Callers of mempool_alloc() will
> be responsible for properly initializing the returned element.
>
> Then, it doesn't matter if the element came from the slab cache or the
> mempool reserved pool.
>
> The only occurrence of a mempool being based on a slab cache with an
> object constructor in the tree is in fs/jfs/jfs_metapage.c. Remove it
> and properly initialize the element in alloc_metapage().
>
> At the same time, META_free is never used, so remove it as well.
>
> Signed-off-by: David Rientjes <rientjes@xxxxxxxxxx>
Acked-by: Dave Kleikamp <dave.kleikamp@xxxxxxxxxx>
> ---
> fs/jfs/jfs_metapage.c | 31 ++++++++++++-------------------
> fs/jfs/jfs_metapage.h | 1 -
> 2 files changed, 12 insertions(+), 20 deletions(-)
>
> diff --git a/fs/jfs/jfs_metapage.c b/fs/jfs/jfs_metapage.c
> --- a/fs/jfs/jfs_metapage.c
> +++ b/fs/jfs/jfs_metapage.c
> @@ -183,30 +183,23 @@ static inline void remove_metapage(struct page *page, struct metapage *mp)
>
> #endif
>
> -static void init_once(void *foo)
> -{
> - struct metapage *mp = (struct metapage *)foo;
> -
> - mp->lid = 0;
> - mp->lsn = 0;
> - mp->flag = 0;
> - mp->data = NULL;
> - mp->clsn = 0;
> - mp->log = NULL;
> - set_bit(META_free, &mp->flag);
> - init_waitqueue_head(&mp->wait);
> -}
> -
> static inline struct metapage *alloc_metapage(gfp_t gfp_mask)
> {
> - return mempool_alloc(metapage_mempool, gfp_mask);
> + struct metapage *mp = mempool_alloc(metapage_mempool, gfp_mask);
> +
> + if (mp) {
> + mp->lid = 0;
> + mp->lsn = 0;
> + mp->data = NULL;
> + mp->clsn = 0;
> + mp->log = NULL;
> + init_waitqueue_head(&mp->wait);
> + }
> + return mp;
> }
>
> static inline void free_metapage(struct metapage *mp)
> {
> - mp->flag = 0;
> - set_bit(META_free, &mp->flag);
> -
> mempool_free(mp, metapage_mempool);
> }
>
> @@ -216,7 +209,7 @@ int __init metapage_init(void)
> * Allocate the metapage structures
> */
> metapage_cache = kmem_cache_create("jfs_mp", sizeof(struct metapage),
> - 0, 0, init_once);
> + 0, 0, NULL);
> if (metapage_cache == NULL)
> return -ENOMEM;
>
> diff --git a/fs/jfs/jfs_metapage.h b/fs/jfs/jfs_metapage.h
> --- a/fs/jfs/jfs_metapage.h
> +++ b/fs/jfs/jfs_metapage.h
> @@ -48,7 +48,6 @@ struct metapage {
>
> /* metapage flag */
> #define META_locked 0
> -#define META_free 1
> #define META_dirty 2
> #define META_sync 3
> #define META_discard 4
>
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