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    Subject[PATCH v7 44/61] shmem: Convert replace to XArray
    Date
    From: Matthew Wilcox <mawilcox@microsoft.com>

    shmem_radix_tree_replace() is renamed to shmem_xa_replace() and
    converted to use the XArray API.

    Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
    ---
    mm/shmem.c | 22 ++++++++--------------
    1 file changed, 8 insertions(+), 14 deletions(-)

    diff --git a/mm/shmem.c b/mm/shmem.c
    index 2616f2d3be95..a8db3241f826 100644
    --- a/mm/shmem.c
    +++ b/mm/shmem.c
    @@ -321,24 +321,20 @@ void shmem_uncharge(struct inode *inode, long pages)
    }

    /*
    - * Replace item expected in radix tree by a new item, while holding tree lock.
    + * Replace item expected in xarray by a new item, while holding xa_lock.
    */
    -static int shmem_radix_tree_replace(struct address_space *mapping,
    +static int shmem_xa_replace(struct address_space *mapping,
    pgoff_t index, void *expected, void *replacement)
    {
    - struct radix_tree_node *node;
    - void **pslot;
    + XA_STATE(xas, &mapping->pages, index);
    void *item;

    VM_BUG_ON(!expected);
    VM_BUG_ON(!replacement);
    - item = __radix_tree_lookup(&mapping->pages, index, &node, &pslot);
    - if (!item)
    - return -ENOENT;
    + item = xas_load(&xas);
    if (item != expected)
    return -ENOENT;
    - __radix_tree_replace(&mapping->pages, node, pslot,
    - replacement, NULL);
    + xas_store(&xas, replacement);
    return 0;
    }

    @@ -605,8 +601,7 @@ static int shmem_add_to_page_cache(struct page *page,
    } else if (!expected) {
    error = radix_tree_insert(&mapping->pages, index, page);
    } else {
    - error = shmem_radix_tree_replace(mapping, index, expected,
    - page);
    + error = shmem_xa_replace(mapping, index, expected, page);
    }

    if (!error) {
    @@ -635,7 +630,7 @@ static void shmem_delete_from_page_cache(struct page *page, void *radswap)
    VM_BUG_ON_PAGE(PageCompound(page), page);

    xa_lock_irq(&mapping->pages);
    - error = shmem_radix_tree_replace(mapping, page->index, page, radswap);
    + error = shmem_xa_replace(mapping, page->index, page, radswap);
    page->mapping = NULL;
    mapping->nrpages--;
    __dec_node_page_state(page, NR_FILE_PAGES);
    @@ -1550,8 +1545,7 @@ static int shmem_replace_page(struct page **pagep, gfp_t gfp,
    * a nice clean interface for us to replace oldpage by newpage there.
    */
    xa_lock_irq(&swap_mapping->pages);
    - error = shmem_radix_tree_replace(swap_mapping, swap_index, oldpage,
    - newpage);
    + error = shmem_xa_replace(swap_mapping, swap_index, oldpage, newpage);
    if (!error) {
    __inc_node_page_state(newpage, NR_FILE_PAGES);
    __dec_node_page_state(oldpage, NR_FILE_PAGES);
    --
    2.16.1
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