| Message ID | 20240923231142.4155415-3-nphamcs@gmail.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | remove SWAP_MAP_SHMEM | expand |
On Mon, Sep 23, 2024 at 4:11 PM Nhat Pham <nphamcs@gmail.com> wrote: > > The SWAP_MAP_SHMEM state was introduced in the commit aaa468653b4a > ("swap_info: note SWAP_MAP_SHMEM"), to quickly determine if a swap entry > belongs to shmem during swapoff. > > However, swapoff has since been rewritten in the commit b56a2d8af914 > ("mm: rid swapoff of quadratic complexity"). Now having swap count == > SWAP_MAP_SHMEM value is basically the same as having swap count == 1, > and swap_shmem_alloc() behaves analogously to swap_duplicate(). It's probably useful to point out that swap_shmem_alloc() is equivalent to swap_duplicate() because __swap_duplicate() should never return -ENOMEM for shmem, as we only ever increment the swap count by 1 (for each entry). > > Remove this state and the associated helper to simplify the state > machine (both mentally and in terms of actual code). We will also have > an extra state/special value that can be repurposed (for swap entries > that never gets re-duplicated). > > Signed-off-by: Nhat Pham <nphamcs@gmail.com> > --- > include/linux/swap.h | 6 ------ > mm/shmem.c | 2 +- > mm/swapfile.c | 15 --------------- > 3 files changed, 1 insertion(+), 22 deletions(-) > > diff --git a/include/linux/swap.h b/include/linux/swap.h > index e6ab234be7be..017f3c03ff7a 100644 > --- a/include/linux/swap.h > +++ b/include/linux/swap.h > @@ -232,7 +232,6 @@ enum { > /* Special value in first swap_map */ > #define SWAP_MAP_MAX 0x3e /* Max count */ > #define SWAP_MAP_BAD 0x3f /* Note page is bad */ > -#define SWAP_MAP_SHMEM 0xbf /* Owned by shmem/tmpfs */ > > /* Special value in each swap_map continuation */ > #define SWAP_CONT_MAX 0x7f /* Max count */ > @@ -482,7 +481,6 @@ void put_swap_folio(struct folio *folio, swp_entry_t entry); > extern swp_entry_t get_swap_page_of_type(int); > extern int get_swap_pages(int n, swp_entry_t swp_entries[], int order); > extern int add_swap_count_continuation(swp_entry_t, gfp_t); > -extern void swap_shmem_alloc(swp_entry_t, int); > extern int swap_duplicate_nr(swp_entry_t, int); > extern int swapcache_prepare(swp_entry_t entry, int nr); > extern void swap_free_nr(swp_entry_t entry, int nr_pages); > @@ -549,10 +547,6 @@ static inline int add_swap_count_continuation(swp_entry_t swp, gfp_t gfp_mask) > return 0; > } > > -static inline void swap_shmem_alloc(swp_entry_t swp, int nr) > -{ > -} > - > static inline int swap_duplicate_nr(swp_entry_t swp, int nr) > { > return 0; > diff --git a/mm/shmem.c b/mm/shmem.c > index 361affdf3990..1875f2521dc6 100644 > --- a/mm/shmem.c > +++ b/mm/shmem.c > @@ -1559,7 +1559,7 @@ static int shmem_writepage(struct page *page, struct writeback_control *wbc) > __GFP_HIGH | __GFP_NOMEMALLOC | __GFP_NOWARN, > NULL) == 0) { > shmem_recalc_inode(inode, 0, nr_pages); > - swap_shmem_alloc(swap, nr_pages); > + swap_duplicate_nr(swap, nr_pages); > shmem_delete_from_page_cache(folio, swp_to_radix_entry(swap)); > > mutex_unlock(&shmem_swaplist_mutex); > diff --git a/mm/swapfile.c b/mm/swapfile.c > index 47a2cd5f590d..cebc244ee60f 100644 > --- a/mm/swapfile.c > +++ b/mm/swapfile.c > @@ -1381,12 +1381,6 @@ static unsigned char __swap_entry_free_locked(struct swap_info_struct *si, > if (usage == SWAP_HAS_CACHE) { > VM_BUG_ON(!has_cache); > has_cache = 0; > - } else if (count == SWAP_MAP_SHMEM) { > - /* > - * Or we could insist on shmem.c using a special > - * swap_shmem_free() and free_shmem_swap_and_cache()... > - */ > - count = 0; > } else if ((count & ~COUNT_CONTINUED) <= SWAP_MAP_MAX) { > if (count == COUNT_CONTINUED) { > if (swap_count_continued(si, offset, count)) > @@ -3686,15 +3680,6 @@ static int __swap_duplicate(swp_entry_t entry, unsigned char usage, int nr) > return err; > } > > -/* > - * Help swapoff by noting that swap entry belongs to shmem/tmpfs > - * (in which case its reference count is never incremented). > - */ > -void swap_shmem_alloc(swp_entry_t entry, int nr) > -{ > - __swap_duplicate(entry, SWAP_MAP_SHMEM, nr); > -} > - > /** > * swap_duplicate_nr() - Increase reference count of nr contiguous swap entries > * by 1. > -- > 2.43.5
diff --git a/include/linux/swap.h b/include/linux/swap.h index e6ab234be7be..017f3c03ff7a 100644 --- a/include/linux/swap.h +++ b/include/linux/swap.h @@ -232,7 +232,6 @@ enum { /* Special value in first swap_map */ #define SWAP_MAP_MAX 0x3e /* Max count */ #define SWAP_MAP_BAD 0x3f /* Note page is bad */ -#define SWAP_MAP_SHMEM 0xbf /* Owned by shmem/tmpfs */ /* Special value in each swap_map continuation */ #define SWAP_CONT_MAX 0x7f /* Max count */ @@ -482,7 +481,6 @@ void put_swap_folio(struct folio *folio, swp_entry_t entry); extern swp_entry_t get_swap_page_of_type(int); extern int get_swap_pages(int n, swp_entry_t swp_entries[], int order); extern int add_swap_count_continuation(swp_entry_t, gfp_t); -extern void swap_shmem_alloc(swp_entry_t, int); extern int swap_duplicate_nr(swp_entry_t, int); extern int swapcache_prepare(swp_entry_t entry, int nr); extern void swap_free_nr(swp_entry_t entry, int nr_pages); @@ -549,10 +547,6 @@ static inline int add_swap_count_continuation(swp_entry_t swp, gfp_t gfp_mask) return 0; } -static inline void swap_shmem_alloc(swp_entry_t swp, int nr) -{ -} - static inline int swap_duplicate_nr(swp_entry_t swp, int nr) { return 0; diff --git a/mm/shmem.c b/mm/shmem.c index 361affdf3990..1875f2521dc6 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -1559,7 +1559,7 @@ static int shmem_writepage(struct page *page, struct writeback_control *wbc) __GFP_HIGH | __GFP_NOMEMALLOC | __GFP_NOWARN, NULL) == 0) { shmem_recalc_inode(inode, 0, nr_pages); - swap_shmem_alloc(swap, nr_pages); + swap_duplicate_nr(swap, nr_pages); shmem_delete_from_page_cache(folio, swp_to_radix_entry(swap)); mutex_unlock(&shmem_swaplist_mutex); diff --git a/mm/swapfile.c b/mm/swapfile.c index 47a2cd5f590d..cebc244ee60f 100644 --- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -1381,12 +1381,6 @@ static unsigned char __swap_entry_free_locked(struct swap_info_struct *si, if (usage == SWAP_HAS_CACHE) { VM_BUG_ON(!has_cache); has_cache = 0; - } else if (count == SWAP_MAP_SHMEM) { - /* - * Or we could insist on shmem.c using a special - * swap_shmem_free() and free_shmem_swap_and_cache()... - */ - count = 0; } else if ((count & ~COUNT_CONTINUED) <= SWAP_MAP_MAX) { if (count == COUNT_CONTINUED) { if (swap_count_continued(si, offset, count)) @@ -3686,15 +3680,6 @@ static int __swap_duplicate(swp_entry_t entry, unsigned char usage, int nr) return err; } -/* - * Help swapoff by noting that swap entry belongs to shmem/tmpfs - * (in which case its reference count is never incremented). - */ -void swap_shmem_alloc(swp_entry_t entry, int nr) -{ - __swap_duplicate(entry, SWAP_MAP_SHMEM, nr); -} - /** * swap_duplicate_nr() - Increase reference count of nr contiguous swap entries * by 1.
The SWAP_MAP_SHMEM state was introduced in the commit aaa468653b4a ("swap_info: note SWAP_MAP_SHMEM"), to quickly determine if a swap entry belongs to shmem during swapoff. However, swapoff has since been rewritten in the commit b56a2d8af914 ("mm: rid swapoff of quadratic complexity"). Now having swap count == SWAP_MAP_SHMEM value is basically the same as having swap count == 1, and swap_shmem_alloc() behaves analogously to swap_duplicate(). Remove this state and the associated helper to simplify the state machine (both mentally and in terms of actual code). We will also have an extra state/special value that can be repurposed (for swap entries that never gets re-duplicated). Signed-off-by: Nhat Pham <nphamcs@gmail.com> --- include/linux/swap.h | 6 ------ mm/shmem.c | 2 +- mm/swapfile.c | 15 --------------- 3 files changed, 1 insertion(+), 22 deletions(-)