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    Subject[PATCH 14/28] mm: reclaim_state records pages reclaimed, not slabs
    Date
    From: Dave Chinner <dchinner@redhat.com>

    Add a wrapper to account for page freeing in shrinker reclaim so
    that the high level scanning accounts for all the memory freed
    during a shrinker scan.

    No logic changes, just replacing open coded checks with a simple
    wrapper.

    Signed-off-by: Dave Chinner <dchinner@redhat.com>
    ---
    fs/inode.c | 3 +--
    fs/xfs/xfs_buf.c | 4 +---
    include/linux/swap.h | 20 ++++++++++++++++++--
    mm/slab.c | 3 +--
    mm/slob.c | 4 +---
    mm/slub.c | 3 +--
    mm/vmscan.c | 4 ++--
    7 files changed, 25 insertions(+), 16 deletions(-)

    diff --git a/fs/inode.c b/fs/inode.c
    index fef457a42882..a77caf216659 100644
    --- a/fs/inode.c
    +++ b/fs/inode.c
    @@ -764,8 +764,7 @@ static enum lru_status inode_lru_isolate(struct list_head *item,
    __count_vm_events(KSWAPD_INODESTEAL, reap);
    else
    __count_vm_events(PGINODESTEAL, reap);
    - if (current->reclaim_state)
    - current->reclaim_state->reclaimed_slab += reap;
    + current_reclaim_account_pages(reap);
    }
    iput(inode);
    spin_lock(lru_lock);
    diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c
    index d34e5d2edacd..55b082bc53b3 100644
    --- a/fs/xfs/xfs_buf.c
    +++ b/fs/xfs/xfs_buf.c
    @@ -324,9 +324,7 @@ xfs_buf_free(

    __free_page(page);
    }
    - if (current->reclaim_state)
    - current->reclaim_state->reclaimed_slab +=
    - bp->b_page_count;
    + current_reclaim_account_pages(bp->b_page_count);
    } else if (bp->b_flags & _XBF_KMEM)
    kmem_free(bp->b_addr);
    _xfs_buf_free_pages(bp);
    diff --git a/include/linux/swap.h b/include/linux/swap.h
    index 063c0c1e112b..72b855fe20b0 100644
    --- a/include/linux/swap.h
    +++ b/include/linux/swap.h
    @@ -126,12 +126,28 @@ union swap_header {

    /*
    * current->reclaim_state points to one of these when a task is running
    - * memory reclaim
    + * memory reclaim. It is typically used by shrinkers to return reclaim
    + * information back to the main vmscan loop.
    */
    struct reclaim_state {
    - unsigned long reclaimed_slab;
    + unsigned long reclaimed_pages; /* pages freed by shrinkers */
    };

    +/*
    + * When code frees a page that may be run from a memory reclaim context, it
    + * needs to account for the pages it frees so memory reclaim can track them.
    + * Slab memory that is freed is accounted via this mechanism, so this is not
    + * necessary for slab or heap memory being freed. However, if the object being
    + * freed frees pages directly, then those pages should be accounted as well when
    + * in memory reclaim. This helper function takes care accounting for the pages
    + * being reclaimed when it is required.
    + */
    +static inline void current_reclaim_account_pages(int nr_pages)
    +{
    + if (current->reclaim_state)
    + current->reclaim_state->reclaimed_pages += nr_pages;
    +}
    +
    #ifdef __KERNEL__

    struct address_space;
    diff --git a/mm/slab.c b/mm/slab.c
    index 66e5d8032bae..419be005f41a 100644
    --- a/mm/slab.c
    +++ b/mm/slab.c
    @@ -1395,8 +1395,7 @@ static void kmem_freepages(struct kmem_cache *cachep, struct page *page)
    page_mapcount_reset(page);
    page->mapping = NULL;

    - if (current->reclaim_state)
    - current->reclaim_state->reclaimed_slab += 1 << order;
    + current_reclaim_account_pages(1 << order);
    uncharge_slab_page(page, order, cachep);
    __free_pages(page, order);
    }
    diff --git a/mm/slob.c b/mm/slob.c
    index fa53e9f73893..c54a7eeee86d 100644
    --- a/mm/slob.c
    +++ b/mm/slob.c
    @@ -211,9 +211,7 @@ static void slob_free_pages(void *b, int order)
    {
    struct page *sp = virt_to_page(b);

    - if (current->reclaim_state)
    - current->reclaim_state->reclaimed_slab += 1 << order;
    -
    + current_reclaim_account_pages(1 << order);
    mod_node_page_state(page_pgdat(sp), NR_SLAB_UNRECLAIMABLE,
    -(1 << order));
    __free_pages(sp, order);
    diff --git a/mm/slub.c b/mm/slub.c
    index b25c807a111f..478554082079 100644
    --- a/mm/slub.c
    +++ b/mm/slub.c
    @@ -1746,8 +1746,7 @@ static void __free_slab(struct kmem_cache *s, struct page *page)
    __ClearPageSlab(page);

    page->mapping = NULL;
    - if (current->reclaim_state)
    - current->reclaim_state->reclaimed_slab += pages;
    + current_reclaim_account_pages(pages);
    uncharge_slab_page(page, order, s);
    __free_pages(page, order);
    }
    diff --git a/mm/vmscan.c b/mm/vmscan.c
    index 7a8256322150..967e3d3c7748 100644
    --- a/mm/vmscan.c
    +++ b/mm/vmscan.c
    @@ -2870,8 +2870,8 @@ static bool shrink_node(pg_data_t *pgdat, struct scan_control *sc)
    } while ((memcg = mem_cgroup_iter(root, memcg, NULL)));

    if (reclaim_state) {
    - sc->nr_reclaimed += reclaim_state->reclaimed_slab;
    - reclaim_state->reclaimed_slab = 0;
    + sc->nr_reclaimed += reclaim_state->reclaimed_pages;
    + reclaim_state->reclaimed_pages = 0;
    }

    /* Record the subtree's reclaim efficiency */
    --
    2.24.0.rc0
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