Barry Song <21cnbao@xxxxxxxxx> writes:
> On Thu, Aug 1, 2024 at 2:50 PM Huang, Ying <ying.huang@xxxxxxxxx> wrote:
>>
>> Barry Song <21cnbao@xxxxxxxxx> writes:
>>
>> > On Thu, Aug 1, 2024 at 10:37 AM Huang, Ying <ying.huang@xxxxxxxxx> wrote:
>> >>
>> >> Barry Song <21cnbao@xxxxxxxxx> writes:
>> >>
>> >> > On Thu, Aug 1, 2024 at 9:13 AM Huang, Ying <ying.huang@xxxxxxxxx> wrote:
>> >> >>
>> >> >> Barry Song <21cnbao@xxxxxxxxx> writes:
>> >> >>
>> >> >> > On Wed, Jul 31, 2024 at 4:28 PM Huang, Ying <ying.huang@xxxxxxxxx> wrote:
>> >> >> >>
>> >> >> >> Barry Song <21cnbao@xxxxxxxxx> writes:
>> >> >> >>
>> >> >> >> > On Wed, Jul 31, 2024 at 4:14 PM Huang, Ying <ying.huang@xxxxxxxxx> wrote:
>> >> >> >> >>
>> >> >> >> >> Hi, Barry,
>> >> >> >> >>
>> >> >> >> >> Barry Song <21cnbao@xxxxxxxxx> writes:
>> >> >> >> >>
>> >> >> >> >> > From: Barry Song <v-songbaohua@xxxxxxxx>
>> >> >> >> >> >
>> >> >> >> >> > Right now, swapcache_prepare() and swapcache_clear() supports one entry
>> >> >> >> >> > only, to support large folios, we need to handle multiple swap entries.
>> >> >> >> >> >
>> >> >> >> >> > To optimize stack usage, we iterate twice in __swap_duplicate(): the
>> >> >> >> >> > first time to verify that all entries are valid, and the second time
>> >> >> >> >> > to apply the modifications to the entries.
>> >> >> >> >> >
>> >> >> >> >> > Currently, we're using nr=1 for the existing users.
>> >> >> >> >> >
>> >> >> >> >> > Reviewed-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>
>> >> >> >> >> > Signed-off-by: Barry Song <v-songbaohua@xxxxxxxx>
>> >> >> >> >> > ---
>> >> >> >> >> > include/linux/swap.h | 4 +-
>> >> >> >> >> > mm/memory.c | 6 +--
>> >> >> >> >> > mm/swap.h | 5 ++-
>> >> >> >> >> > mm/swap_state.c | 2 +-
>> >> >> >> >> > mm/swapfile.c | 101 +++++++++++++++++++++++++------------------
>> >> >> >> >> > 5 files changed, 68 insertions(+), 50 deletions(-)
>> >> >> >> >> >
>> >> >> >> >> > diff --git a/include/linux/swap.h b/include/linux/swap.h
>> >> >> >> >> > index ba7ea95d1c57..5b920fa2315b 100644
>> >> >> >> >> > --- a/include/linux/swap.h
>> >> >> >> >> > +++ b/include/linux/swap.h
>> >> >> >> >> > @@ -480,7 +480,7 @@ 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);
>> >> >> >> >> > extern int swap_duplicate(swp_entry_t);
>> >> >> >> >> > -extern int swapcache_prepare(swp_entry_t);
>> >> >> >> >> > +extern int swapcache_prepare(swp_entry_t entry, int nr);
>> >> >> >> >> > extern void swap_free_nr(swp_entry_t entry, int nr_pages);
>> >> >> >> >> > extern void swapcache_free_entries(swp_entry_t *entries, int n);
>> >> >> >> >> > extern void free_swap_and_cache_nr(swp_entry_t entry, int nr);
>> >> >> >> >> > @@ -554,7 +554,7 @@ static inline int swap_duplicate(swp_entry_t swp)
>> >> >> >> >> > return 0;
>> >> >> >> >> > }
>> >> >> >> >> >
>> >> >> >> >> > -static inline int swapcache_prepare(swp_entry_t swp)
>> >> >> >> >> > +static inline int swapcache_prepare(swp_entry_t swp, int nr)
>> >> >> >> >> > {
>> >> >> >> >> > return 0;
>> >> >> >> >> > }
>> >> >> >> >> > diff --git a/mm/memory.c b/mm/memory.c
>> >> >> >> >> > index 833d2cad6eb2..b8675617a5e3 100644
>> >> >> >> >> > --- a/mm/memory.c
>> >> >> >> >> > +++ b/mm/memory.c
>> >> >> >> >> > @@ -4081,7 +4081,7 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
>> >> >> >> >> > * reusing the same entry. It's undetectable as
>> >> >> >> >> > * pte_same() returns true due to entry reuse.
>> >> >> >> >> > */
>> >> >> >> >> > - if (swapcache_prepare(entry)) {
>> >> >> >> >> > + if (swapcache_prepare(entry, 1)) {
>> >> >> >> >> > /* Relax a bit to prevent rapid repeated page faults */
>> >> >> >> >> > schedule_timeout_uninterruptible(1);
>> >> >> >> >> > goto out;
>> >> >> >> >> > @@ -4387,7 +4387,7 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
>> >> >> >> >> > out:
>> >> >> >> >> > /* Clear the swap cache pin for direct swapin after PTL unlock */
>> >> >> >> >> > if (need_clear_cache)
>> >> >> >> >> > - swapcache_clear(si, entry);
>> >> >> >> >> > + swapcache_clear(si, entry, 1);
>> >> >> >> >> > if (si)
>> >> >> >> >> > put_swap_device(si);
>> >> >> >> >> > return ret;
>> >> >> >> >> > @@ -4403,7 +4403,7 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
>> >> >> >> >> > folio_put(swapcache);
>> >> >> >> >> > }
>> >> >> >> >> > if (need_clear_cache)
>> >> >> >> >> > - swapcache_clear(si, entry);
>> >> >> >> >> > + swapcache_clear(si, entry, 1);
>> >> >> >> >> > if (si)
>> >> >> >> >> > put_swap_device(si);
>> >> >> >> >> > return ret;
>> >> >> >> >> > diff --git a/mm/swap.h b/mm/swap.h
>> >> >> >> >> > index baa1fa946b34..7c6330561d84 100644
>> >> >> >> >> > --- a/mm/swap.h
>> >> >> >> >> > +++ b/mm/swap.h
>> >> >> >> >> > @@ -59,7 +59,7 @@ void __delete_from_swap_cache(struct folio *folio,
>> >> >> >> >> > void delete_from_swap_cache(struct folio *folio);
>> >> >> >> >> > void clear_shadow_from_swap_cache(int type, unsigned long begin,
>> >> >> >> >> > unsigned long end);
>> >> >> >> >> > -void swapcache_clear(struct swap_info_struct *si, swp_entry_t entry);
>> >> >> >> >> > +void swapcache_clear(struct swap_info_struct *si, swp_entry_t entry, int nr);
>> >> >> >> >> > struct folio *swap_cache_get_folio(swp_entry_t entry,
>> >> >> >> >> > struct vm_area_struct *vma, unsigned long addr);
>> >> >> >> >> > struct folio *filemap_get_incore_folio(struct address_space *mapping,
>> >> >> >> >> > @@ -120,7 +120,7 @@ static inline int swap_writepage(struct page *p, struct writeback_control *wbc)
>> >> >> >> >> > return 0;
>> >> >> >> >> > }
>> >> >> >> >> >
>> >> >> >> >> > -static inline void swapcache_clear(struct swap_info_struct *si, swp_entry_t entry)
>> >> >> >> >> > +static inline void swapcache_clear(struct swap_info_struct *si, swp_entry_t entry, int nr)
>> >> >> >> >> > {
>> >> >> >> >> > }
>> >> >> >> >> >
>> >> >> >> >> > @@ -172,4 +172,5 @@ static inline unsigned int folio_swap_flags(struct folio *folio)
>> >> >> >> >> > return 0;
>> >> >> >> >> > }
>> >> >> >> >> > #endif /* CONFIG_SWAP */
>> >> >> >> >> > +
>> >> >> >> >>
>> >> >> >> >> NITPICK: Is it necessary to add a blank line here? But I don't think a
>> >> >> >> >> new version is necessary if this is the only change needed.
>> >> >> >> >
>> >> >> >> > No need to add a blank line; it was probably a mistake I made in Vim.
>> >> >> >> >
>> >> >> >> >>
>> >> >> >> >> > #endif /* _MM_SWAP_H */
>> >> >> >> >> > diff --git a/mm/swap_state.c b/mm/swap_state.c
>> >> >> >> >> > index a1726e49a5eb..b06f2a054f5a 100644
>> >> >> >> >> > --- a/mm/swap_state.c
>> >> >> >> >> > +++ b/mm/swap_state.c
>> >> >> >> >> > @@ -477,7 +477,7 @@ struct folio *__read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
>> >> >> >> >> > /*
>> >> >> >> >> > * Swap entry may have been freed since our caller observed it.
>> >> >> >> >> > */
>> >> >> >> >> > - err = swapcache_prepare(entry);
>> >> >> >> >> > + err = swapcache_prepare(entry, 1);
>> >> >> >> >> > if (!err)
>> >> >> >> >> > break;
>> >> >> >> >> >
>> >> >> >> >> > diff --git a/mm/swapfile.c b/mm/swapfile.c
>> >> >> >> >> > index 5f73a8553371..757d38a86f56 100644
>> >> >> >> >> > --- a/mm/swapfile.c
>> >> >> >> >> > +++ b/mm/swapfile.c
>> >> >> >> >> > @@ -3363,7 +3363,7 @@ void si_swapinfo(struct sysinfo *val)
>> >> >> >> >> > }
>> >> >> >> >> >
>> >> >> >> >> > /*
>> >> >> >> >> > - * Verify that a swap entry is valid and increment its swap map count.
>> >> >> >> >> > + * Verify that nr swap entries are valid and increment their swap map counts.
>> >> >> >> >> > *
>> >> >> >> >> > * Returns error code in following case.
>> >> >> >> >> > * - success -> 0
>> >> >> >> >> > @@ -3373,60 +3373,77 @@ void si_swapinfo(struct sysinfo *val)
>> >> >> >> >> > * - swap-cache reference is requested but the entry is not used. -> ENOENT
>> >> >> >> >> > * - swap-mapped reference requested but needs continued swap count. -> ENOMEM
>> >> >> >> >> > */
>> >> >> >> >> > -static int __swap_duplicate(swp_entry_t entry, unsigned char usage)
>> >> >> >> >> > +static int __swap_duplicate(swp_entry_t entry, unsigned char usage, int nr)
>> >> >> >> >> > {
>> >> >> >> >> > struct swap_info_struct *p;
>> >> >> >> >> > struct swap_cluster_info *ci;
>> >> >> >> >> > unsigned long offset;
>> >> >> >> >> > unsigned char count;
>> >> >> >> >> > unsigned char has_cache;
>> >> >> >> >> > - int err;
>> >> >> >> >> > + int err, i;
>> >> >> >> >> >
>> >> >> >> >> > p = swp_swap_info(entry);
>> >> >> >> >> >
>> >> >> >> >> > offset = swp_offset(entry);
>> >> >> >> >> > + VM_WARN_ON(nr > SWAPFILE_CLUSTER - offset % SWAPFILE_CLUSTER);
>> >> >> >> >> > ci = lock_cluster_or_swap_info(p, offset);
>> >> >> >> >> >
>> >> >> >> >> > - count = p->swap_map[offset];
>> >> >> >> >> > + err = 0;
>> >> >> >> >> > + for (i = 0; i < nr; i++) {
>> >> >> >> >> > + count = p->swap_map[offset + i];
>> >> >> >> >> >
>> >> >> >> >> > - /*
>> >> >> >> >> > - * swapin_readahead() doesn't check if a swap entry is valid, so the
>> >> >> >> >> > - * swap entry could be SWAP_MAP_BAD. Check here with lock held.
>> >> >> >> >> > - */
>> >> >> >> >> > - if (unlikely(swap_count(count) == SWAP_MAP_BAD)) {
>> >> >> >> >> > - err = -ENOENT;
>> >> >> >> >> > - goto unlock_out;
>> >> >> >> >> > - }
>> >> >> >> >> > + /*
>> >> >> >> >> > + * swapin_readahead() doesn't check if a swap entry is valid, so the
>> >> >> >> >> > + * swap entry could be SWAP_MAP_BAD. Check here with lock held.
>> >> >> >> >> > + */
>> >> >> >> >> > + if (unlikely(swap_count(count) == SWAP_MAP_BAD)) {
>> >> >> >> >> > + err = -ENOENT;
>> >> >> >> >> > + goto unlock_out;
>> >> >> >> >> > + }
>> >> >> >> >> >
>> >> >> >> >> > - has_cache = count & SWAP_HAS_CACHE;
>> >> >> >> >> > - count &= ~SWAP_HAS_CACHE;
>> >> >> >> >> > - err = 0;
>> >> >> >> >> > + has_cache = count & SWAP_HAS_CACHE;
>> >> >> >> >> > + count &= ~SWAP_HAS_CACHE;
>> >> >> >> >> >
>> >> >> >> >> > - if (usage == SWAP_HAS_CACHE) {
>> >> >> >> >> > + if (usage == SWAP_HAS_CACHE) {
>> >> >> >> >> > + /* set SWAP_HAS_CACHE if there is no cache and entry is used */
>> >> >> >> >> > + if (!has_cache && count)
>> >> >> >> >> > + continue;
>> >> >> >> >> > + else if (has_cache) /* someone else added cache */
>> >> >> >> >> > + err = -EEXIST;
>> >> >> >> >> > + else /* no users remaining */
>> >> >> >> >> > + err = -ENOENT;
>> >> >> >> >> >
>> >> >> >> >> > - /* set SWAP_HAS_CACHE if there is no cache and entry is used */
>> >> >> >> >> > - if (!has_cache && count)
>> >> >> >> >> > - has_cache = SWAP_HAS_CACHE;
>> >> >> >> >> > - else if (has_cache) /* someone else added cache */
>> >> >> >> >> > - err = -EEXIST;
>> >> >> >> >> > - else /* no users remaining */
>> >> >> >> >> > - err = -ENOENT;
>> >> >> >> >> > + } else if (count || has_cache) {
>> >> >> >> >> >
>> >> >> >> >> > - } else if (count || has_cache) {
>> >> >> >> >> > + if ((count & ~COUNT_CONTINUED) < SWAP_MAP_MAX)
>> >> >> >> >> > + continue;
>> >> >> >> >> > + else if ((count & ~COUNT_CONTINUED) > SWAP_MAP_MAX)
>> >> >> >> >> > + err = -EINVAL;
>> >> >> >> >> > + else if (swap_count_continued(p, offset + i, count))
>> >> >> >> >> > + continue;
>> >> >> >> >>
>> >> >> >> >> IIUC, this will make the change to swap map directly instead of
>> >> >> >> >> verification. If the verification failed for some entry later, the
>> >> >> >> >> count will be wrong? Or I missed something?
>> >> >> >> >
>> >> >> >> > To avoid using a bitmap or a larger stack, we actually verify during
>> >> >> >> > the first iteration.
>> >> >> >> > This ensures that by the second iteration, we can safely commit the
>> >> >> >> > modification.
>> >> >> >> >
>> >> >> >> > I actually put some words in the changelog :-)
>> >> >> >> >
>> >> >> >> > To optimize stack usage, we iterate twice in __swap_duplicate(): the
>> >> >> >> > first time to verify that all entries are valid, and the second time
>> >> >> >> > to apply the modifications to the entries.
>> >> >> >>
>> >> >> >> Yes, I have seen it and I think that it is a good strategy.
>> >> >> >>
>> >> >> >> But, IIUC, swap_count_continued() will change the higher bits of the
>> >> >> >> swap_map instead of verifying. Or, my understanding is wrong?
>> >> >> >>
>> >> >> >
>> >> >> > Ying, your understanding is 100% correct. but the code also has nothing
>> >> >> > broken. we didn't extend swap_duplicate() to have argument nr,
>> >> >> > so all users which can set usage=1 will definitely have nr=1.
>> >> >> >
>> >> >> > int swap_duplicate(swp_entry_t entry)
>> >> >> > {
>> >> >> > int err = 0;
>> >> >> >
>> >> >> > while (!err && __swap_duplicate(entry, 1, 1) == -ENOMEM)
>> >> >> > err = add_swap_count_continuation(entry, GFP_ATOMIC);
>> >> >> > return err;
>> >> >> > }
>> >> >>
>> >> >> I understand that we don't have requirements to support "usage == 1 &&
>> >> >> nr > 1" case for __swap_duplicate() at least for now.
>> >> >>
>> >> >> > Maybe I can add a VM_WARN_ON to warn those people who might
>> >> >> > want to extend swap_duplicate()? in that case, things could be quite
>> >> >> > tricky.
>> >> >> >
>> >> >> > --- a/mm/swapfile.c
>> >> >> > +++ b/mm/swapfile.c
>> >> >> > @@ -3386,6 +3386,7 @@ static int __swap_duplicate(swp_entry_t entry,
>> >> >> > unsigned char usage, int nr)
>> >> >> >
>> >> >> > offset = swp_offset(entry);
>> >> >> > VM_WARN_ON(nr > SWAPFILE_CLUSTER - offset % SWAPFILE_CLUSTER);
>> >> >> > + VM_WARN_ON(usage == 1 && nr > 1);
>> >> >> > ci = lock_cluster_or_swap_info(p, offset);
>> >> >> >
>> >> >> > err = 0;
>> >> >>
>> >> >> Please add this. And, I think that we need to make it explicit in patch
>> >> >> description and comments to avoid potential confusing.
>> >> >
>> >> > cool. make sense to me. I will post something for Andrew to squash into.
>> >> >
>> >> >>
>> >> >> And, because it's hard to implement the verify and change strategy if
>> >> >> "usage == 1". Can we only use that strategy for "usage ==
>> >> >> SWAP_HAS_CACHE"?
>> >> >
>> >> > I believe Baolin also needs the case for shmem. I don't feel a strong
>> >> > need to split two logics(1 and non-1) as the code will be quite ugly :-)
>> >>
>> >> Don't need to split like that, it could be something like
>> >>
>> >> for (i = 0; i < nr; i++) {
>> >> if (usage == SWAP_HAS_CACHE) {
>> >> /* Only verify for SWAP_HAS_CACHE */
>> >> }
>> >> }
>> >>
>> >> for (i = 0; i < nr; i++) {
>> >> if (usage == SWAP_HAS_CACHE) {
>> >> } else {
>> >> /* Verify and change for usage == 1 */
>> >> }
>> >> }
>> >>
>> >
>> > but we also have cases where nr can be > 1
>> > __swap_duplicate(entry, SWAP_MAP_SHMEM, 1);
>>
>> If we can do verification for "usage == SWAP_MAP_SHMEM", we can add that
>> in the first loop.
>>
>> That is, we only do verification in the first loop, not do committing.
>> In the second loop, we can ignore verifying if we have done that in the
>> first loop.
>>
>> IMHO, this make code easier to be understood.
>
> Right. I believe the change below can help improve readability and also
> clarify the swap_count_continued() case.
>
> diff --git a/mm/swapfile.c b/mm/swapfile.c
> index 2fa29bdec171..75a89ce18edc 100644
> --- a/mm/swapfile.c
> +++ b/mm/swapfile.c
> @@ -3538,6 +3538,7 @@ static int __swap_duplicate(swp_entry_t entry, unsigned char usage, int nr)
>
> offset = swp_offset(entry);
> VM_WARN_ON(nr > SWAPFILE_CLUSTER - offset % SWAPFILE_CLUSTER);
> + VM_WARN_ON(usage == 1 && nr > 1);
> ci = lock_cluster_or_swap_info(p, offset);
>
> err = 0;
> @@ -3564,17 +3565,9 @@ static int __swap_duplicate(swp_entry_t entry, unsigned char usage, int nr)
> err = -EEXIST;
> else /* no users remaining */
> err = -ENOENT;
> -
> } else if (count || has_cache) {
> -
> - if ((count & ~COUNT_CONTINUED) < SWAP_MAP_MAX)
> - continue;
> - else if ((count & ~COUNT_CONTINUED) > SWAP_MAP_MAX)
> + if ((count & ~COUNT_CONTINUED) > SWAP_MAP_MAX)
> err = -EINVAL;
> - else if (swap_count_continued(p, offset + i, count))
> - continue;
> - else
> - err = -ENOMEM;
> } else
> err = -ENOENT; /* unused swap entry */
>
> @@ -3591,8 +3584,12 @@ static int __swap_duplicate(swp_entry_t entry, unsigned char usage, int nr)
> has_cache = SWAP_HAS_CACHE;
> else if ((count & ~COUNT_CONTINUED) < SWAP_MAP_MAX)
> count += usage;
> - else
> + else if (swap_count_continued(p, offset + i, count))
> count = COUNT_CONTINUED;
> + else {
> + err = -ENOMEM;
> + goto unlock_out;
> + }
>
> WRITE_ONCE(p->swap_map[offset + i], count | has_cache);
> }
>
> This makes the two iterations become:
>
> for (i = 0; i < nr; i++) {
> count = p->swap_map[offset + i];
>
> /*
> * swapin_readahead() doesn't check if a swap entry is valid, so the
> * swap entry could be SWAP_MAP_BAD. Check here with lock held.
> */
> if (unlikely(swap_count(count) == SWAP_MAP_BAD)) {
> err = -ENOENT;
> goto unlock_out;
> }
>
> has_cache = count & SWAP_HAS_CACHE;
> count &= ~SWAP_HAS_CACHE;
>
> if (usage == SWAP_HAS_CACHE) {
> /* set SWAP_HAS_CACHE if there is no cache and entry is used */
The comments doen't apply now, we don't "set" here.
> if (!has_cache && count)
> continue;
> else if (has_cache) /* someone else added cache */
> err = -EEXIST;
> else /* no users remaining */
> err = -ENOENT;
> } else if (count || has_cache) {
> if ((count & ~COUNT_CONTINUED) > SWAP_MAP_MAX)
> err = -EINVAL;
> } else
> err = -ENOENT; /* unused swap entry */
It seems that this can be simplified to:
if (!count && !has_cache) {
err = -ENOENT;
} else if (usage == SWAP_HAS_CACHE) {
if (has_cache)
err = -EEXIST;
} else if ((count & ~COUNT_CONTINUED) > SWAP_MAP_MAX) {
err = -EINVAL;
}
> if (err)
> goto unlock_out;
> }
>
> for (i = 0; i < nr; i++) {
> count = p->swap_map[offset + i];
> has_cache = count & SWAP_HAS_CACHE;
> count &= ~SWAP_HAS_CACHE;
>
> if (usage == SWAP_HAS_CACHE)
> has_cache = SWAP_HAS_CACHE;
> else if ((count & ~COUNT_CONTINUED) < SWAP_MAP_MAX)
> count += usage;
> else if (swap_count_continued(p, offset + i, count))
> count = COUNT_CONTINUED;
> else {
Better to add some comments here,
/*
* Don't need to rollback changes, because if
* usage == 1, there must be nr == 1.
*/
> err = -ENOMEM;
> goto unlock_out;
> }
>
> WRITE_ONCE(p->swap_map[offset + i], count | has_cache);
> }
>
> Ying, do you feel more satisfied with the version above
> compared to the code in mm-unstable?
This looks good to me except some minor comments above. Thanks!
--
Best Regards,
Huang, Ying
> Baolin, I'd also appreciate it if you could re-test your
> shmem case if Ying is okay with the enhancement above.
>
>>
>> --
>> Best Regards,
>> Huang, Ying
>>
>> >> >>
>> >> >> >> >>
>> >> >> >> >> > + else
>> >> >> >> >> > + err = -ENOMEM;
>> >> >> >> >> > + } else
>> >> >> >> >> > + err = -ENOENT; /* unused swap entry */
>> >> >> >> >> >
>> >> >> >> >> > - if ((count & ~COUNT_CONTINUED) < SWAP_MAP_MAX)
>> >> >> >> >> > + if (err)
>> >> >> >> >> > + goto unlock_out;
>> >> >> >> >> > + }
>> >> >> >> >> > +
>> >> >> >> >> > + for (i = 0; i < nr; i++) {
>> >> >> >> >> > + count = p->swap_map[offset + i];
>> >> >> >> >> > + has_cache = count & SWAP_HAS_CACHE;
>> >> >> >> >> > + count &= ~SWAP_HAS_CACHE;
>> >> >> >> >> > +
>> >> >> >> >> > + if (usage == SWAP_HAS_CACHE)
>> >> >> >> >> > + has_cache = SWAP_HAS_CACHE;
>> >> >> >> >> > + else if ((count & ~COUNT_CONTINUED) < SWAP_MAP_MAX)
>> >> >> >> >> > count += usage;
>> >> >> >> >> > - else if ((count & ~COUNT_CONTINUED) > SWAP_MAP_MAX)
>> >> >> >> >> > - err = -EINVAL;
>> >> >> >> >> > - else if (swap_count_continued(p, offset, count))
>> >> >> >> >> > - count = COUNT_CONTINUED;
>> >> >> >> >> > else
>> >> >> >> >> > - err = -ENOMEM;
>> >> >> >> >> > - } else
>> >> >> >> >> > - err = -ENOENT; /* unused swap entry */
>> >> >> >> >> > + count = COUNT_CONTINUED;
>> >> >> >> >> >
>> >> >> >> >> > - if (!err)
>> >> >> >> >> > - WRITE_ONCE(p->swap_map[offset], count | has_cache);
>> >> >> >> >> > + WRITE_ONCE(p->swap_map[offset + i], count | has_cache);
>> >> >> >> >> > + }
>> >> >> >> >> >
>> >> >> >> >> > unlock_out:
>> >> >> >> >> > unlock_cluster_or_swap_info(p, ci);
>> >> >> >> >> > @@ -3439,7 +3456,7 @@ static int __swap_duplicate(swp_entry_t entry, unsigned char usage)
>> >> >> >> >> > */
>> >> >> >> >> > void swap_shmem_alloc(swp_entry_t entry)
>> >> >> >> >> > {
>> >> >> >> >> > - __swap_duplicate(entry, SWAP_MAP_SHMEM);
>> >> >> >> >> > + __swap_duplicate(entry, SWAP_MAP_SHMEM, 1);
>> >> >> >> >> > }
>> >> >> >> >> >
>> >> >> >> >> > /*
>> >> >> >> >> > @@ -3453,29 +3470,29 @@ int swap_duplicate(swp_entry_t entry)
>> >> >> >> >> > {
>> >> >> >> >> > int err = 0;
>> >> >> >> >> >
>> >> >> >> >> > - while (!err && __swap_duplicate(entry, 1) == -ENOMEM)
>> >> >> >> >> > + while (!err && __swap_duplicate(entry, 1, 1) == -ENOMEM)
>> >> >> >> >> > err = add_swap_count_continuation(entry, GFP_ATOMIC);
>> >> >> >> >> > return err;
>> >> >> >> >> > }
>> >> >> >> >> >
>> >> >> >> >> > /*
>> >> >> >> >> > - * @entry: swap entry for which we allocate swap cache.
>> >> >> >> >> > + * @entry: first swap entry from which we allocate nr swap cache.
>> >> >> >> >> > *
>> >> >> >> >> > - * Called when allocating swap cache for existing swap entry,
>> >> >> >> >> > + * Called when allocating swap cache for existing swap entries,
>> >> >> >> >> > * This can return error codes. Returns 0 at success.
>> >> >> >> >> > * -EEXIST means there is a swap cache.
>> >> >> >> >> > * Note: return code is different from swap_duplicate().
>> >> >> >> >> > */
>> >> >> >> >> > -int swapcache_prepare(swp_entry_t entry)
>> >> >> >> >> > +int swapcache_prepare(swp_entry_t entry, int nr)
>> >> >> >> >> > {
>> >> >> >> >> > - return __swap_duplicate(entry, SWAP_HAS_CACHE);
>> >> >> >> >> > + return __swap_duplicate(entry, SWAP_HAS_CACHE, nr);
>> >> >> >> >> > }
>> >> >> >> >> >
>> >> >> >> >> > -void swapcache_clear(struct swap_info_struct *si, swp_entry_t entry)
>> >> >> >> >> > +void swapcache_clear(struct swap_info_struct *si, swp_entry_t entry, int nr)
>> >> >> >> >> > {
>> >> >> >> >> > unsigned long offset = swp_offset(entry);
>> >> >> >> >> >
>> >> >> >> >> > - cluster_swap_free_nr(si, offset, 1, SWAP_HAS_CACHE);
>> >> >> >> >> > + cluster_swap_free_nr(si, offset, nr, SWAP_HAS_CACHE);
>> >> >> >> >> > }
>> >> >> >> >> >
>> >> >> >> >> > struct swap_info_struct *swp_swap_info(swp_entry_t entry)
>> >> >> >> >>
>> >> >> >> >> --
>> >> >> >> >> Best Regards,
>> >> >> >> >> Huang, Ying
>> >> >> >> >
>> >> >
>
> Thanks
> Barry
