Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx> 于2023年12月14日周四 05:59写道：
>
> shmem_swapin_cluster() immediately converts the page back to a folio,
> and swapin_readahead() may as well call folio_file_page() once instead
> of having each function call it.
>
> Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
> ---
> mm/shmem.c | 8 +++-----
> mm/swap.h | 6 +++---
> mm/swap_state.c | 21 ++++++++++-----------
> 3 files changed, 16 insertions(+), 19 deletions(-)
>
> diff --git a/mm/shmem.c b/mm/shmem.c
> index c62f904ba1ca..a4d388973021 100644
> --- a/mm/shmem.c
> +++ b/mm/shmem.c
> @@ -1570,15 +1570,13 @@ static struct folio *shmem_swapin_cluster(swp_entry_t swap, gfp_t gfp,
> {
> struct mempolicy *mpol;
> pgoff_t ilx;
> - struct page *page;
> + struct folio *folio;
>
> mpol = shmem_get_pgoff_policy(info, index, 0, &ilx);
> - page = swap_cluster_readahead(swap, gfp, mpol, ilx);
> + folio = swap_cluster_readahead(swap, gfp, mpol, ilx);
> mpol_cond_put(mpol);
>
> - if (!page)
> - return NULL;
> - return page_folio(page);
> + return folio;
> }
>
> /*
> diff --git a/mm/swap.h b/mm/swap.h
> index 82c68ccb5ab1..758c46ca671e 100644
> --- a/mm/swap.h
> +++ b/mm/swap.h
> @@ -52,8 +52,8 @@ struct folio *read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
> struct folio *__read_swap_cache_async(swp_entry_t entry, gfp_t gfp_flags,
> struct mempolicy *mpol, pgoff_t ilx, bool *new_page_allocated,
> bool skip_if_exists);
> -struct page *swap_cluster_readahead(swp_entry_t entry, gfp_t flag,
> - struct mempolicy *mpol, pgoff_t ilx);
> +struct folio *swap_cluster_readahead(swp_entry_t entry, gfp_t flag,
> + struct mempolicy *mpol, pgoff_t ilx);
> struct page *swapin_readahead(swp_entry_t entry, gfp_t flag,
> struct vm_fault *vmf);
>
> @@ -80,7 +80,7 @@ static inline void show_swap_cache_info(void)
> {
> }
>
> -static inline struct page *swap_cluster_readahead(swp_entry_t entry,
> +static inline struct folio *swap_cluster_readahead(swp_entry_t entry,
> gfp_t gfp_mask, struct mempolicy *mpol, pgoff_t ilx)
> {
> return NULL;
> diff --git a/mm/swap_state.c b/mm/swap_state.c
> index 1cb1d5d0583e..793b5b9e4f96 100644
> --- a/mm/swap_state.c
> +++ b/mm/swap_state.c
> @@ -629,7 +629,7 @@ static unsigned long swapin_nr_pages(unsigned long offset)
> * @mpol: NUMA memory allocation policy to be applied
> * @ilx: NUMA interleave index, for use only when MPOL_INTERLEAVE
> *
> - * Returns the struct page for entry and addr, after queueing swapin.
> + * Returns the struct folio for entry and addr, after queueing swapin.
> *
> * Primitive swap readahead code. We simply read an aligned block of
> * (1 << page_cluster) entries in the swap area. This method is chosen
> @@ -640,7 +640,7 @@ static unsigned long swapin_nr_pages(unsigned long offset)
> * are used for every page of the readahead: neighbouring pages on swap
> * are fairly likely to have been swapped out from the same node.
> */
> -struct page *swap_cluster_readahead(swp_entry_t entry, gfp_t gfp_mask,
> +struct folio *swap_cluster_readahead(swp_entry_t entry, gfp_t gfp_mask,
> struct mempolicy *mpol, pgoff_t ilx)
> {
> struct folio *folio;
> @@ -692,7 +692,7 @@ struct page *swap_cluster_readahead(swp_entry_t entry, gfp_t gfp_mask,
> if (unlikely(page_allocated))
> swap_read_folio(folio, false, NULL);
> zswap_folio_swapin(folio);
> - return folio_file_page(folio, swp_offset(entry));
> + return folio;
> }
>
> int init_swap_address_space(unsigned int type, unsigned long nr_pages)
> @@ -796,7 +796,7 @@ static void swap_ra_info(struct vm_fault *vmf,
> * @targ_ilx: NUMA interleave index, for use only when MPOL_INTERLEAVE
> * @vmf: fault information
> *
> - * Returns the struct page for entry and addr, after queueing swapin.
> + * Returns the struct folio for entry and addr, after queueing swapin.
> *
> * Primitive swap readahead code. We simply read in a few pages whose
> * virtual addresses are around the fault address in the same vma.
> @@ -804,9 +804,8 @@ static void swap_ra_info(struct vm_fault *vmf,
> * Caller must hold read mmap_lock if vmf->vma is not NULL.
> *
> */
> -static struct page *swap_vma_readahead(swp_entry_t targ_entry, gfp_t gfp_mask,
> - struct mempolicy *mpol, pgoff_t targ_ilx,
> - struct vm_fault *vmf)
> +static struct folio *swap_vma_readahead(swp_entry_t targ_entry, gfp_t gfp_mask,
> + struct mempolicy *mpol, pgoff_t targ_ilx, struct vm_fault *vmf)
> {
> struct blk_plug plug;
> struct swap_iocb *splug = NULL;
> @@ -868,7 +867,7 @@ static struct page *swap_vma_readahead(swp_entry_t targ_entry, gfp_t gfp_mask,
> if (unlikely(page_allocated))
> swap_read_folio(folio, false, NULL);
> zswap_folio_swapin(folio);
> - return folio_file_page(folio, swp_offset(entry));
> + return folio;
> }
>
> /**
> @@ -888,14 +887,14 @@ struct page *swapin_readahead(swp_entry_t entry, gfp_t gfp_mask,
> {
> struct mempolicy *mpol;
> pgoff_t ilx;
> - struct page *page;
> + struct folio *folio;
>
> mpol = get_vma_policy(vmf->vma, vmf->address, 0, &ilx);
> - page = swap_use_vma_readahead() ?
> + folio = swap_use_vma_readahead() ?
> swap_vma_readahead(entry, gfp_mask, mpol, ilx, vmf) :
> swap_cluster_readahead(entry, gfp_mask, mpol, ilx);
> mpol_cond_put(mpol);
> - return page;
> + return folio_file_page(folio, swp_offset(entry));
Hi Matthew,
There is a bug here, folio could be NULL, and cause NULL dereference.
