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    Subject[PATCH v11 1/7] mm: adjust address_space_operations.migratepage() return code
    Date
    This patch introduces MIGRATEPAGE_SUCCESS as the default return code
    for address_space_operations.migratepage() method and documents the
    expected return code for the same method in failure cases.

    Signed-off-by: Rafael Aquini <aquini@redhat.com>
    ---
    fs/hugetlbfs/inode.c | 4 ++--
    include/linux/migrate.h | 7 +++++++
    mm/migrate.c | 22 +++++++++++-----------
    3 files changed, 20 insertions(+), 13 deletions(-)

    diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
    index c5bc355..bdeda2c 100644
    --- a/fs/hugetlbfs/inode.c
    +++ b/fs/hugetlbfs/inode.c
    @@ -608,11 +608,11 @@ static int hugetlbfs_migrate_page(struct address_space *mapping,
    int rc;

    rc = migrate_huge_page_move_mapping(mapping, newpage, page);
    - if (rc)
    + if (rc != MIGRATEPAGE_SUCCESS)
    return rc;
    migrate_page_copy(newpage, page);

    - return 0;
    + return MIGRATEPAGE_SUCCESS;
    }

    static int hugetlbfs_statfs(struct dentry *dentry, struct kstatfs *buf)
    diff --git a/include/linux/migrate.h b/include/linux/migrate.h
    index ce7e667..a4e886d 100644
    --- a/include/linux/migrate.h
    +++ b/include/linux/migrate.h
    @@ -7,6 +7,13 @@

    typedef struct page *new_page_t(struct page *, unsigned long private, int **);

    +/*
    + * Return values from addresss_space_operations.migratepage():
    + * - negative errno on page migration failure;
    + * - zero on page migration success;
    + */
    +#define MIGRATEPAGE_SUCCESS 0
    +
    #ifdef CONFIG_MIGRATION

    extern void putback_lru_pages(struct list_head *l);
    diff --git a/mm/migrate.c b/mm/migrate.c
    index 77ed2d7..98c7a89 100644
    --- a/mm/migrate.c
    +++ b/mm/migrate.c
    @@ -286,7 +286,7 @@ static int migrate_page_move_mapping(struct address_space *mapping,
    /* Anonymous page without mapping */
    if (page_count(page) != 1)
    return -EAGAIN;
    - return 0;
    + return MIGRATEPAGE_SUCCESS;
    }

    spin_lock_irq(&mapping->tree_lock);
    @@ -356,7 +356,7 @@ static int migrate_page_move_mapping(struct address_space *mapping,
    }
    spin_unlock_irq(&mapping->tree_lock);

    - return 0;
    + return MIGRATEPAGE_SUCCESS;
    }

    /*
    @@ -372,7 +372,7 @@ int migrate_huge_page_move_mapping(struct address_space *mapping,
    if (!mapping) {
    if (page_count(page) != 1)
    return -EAGAIN;
    - return 0;
    + return MIGRATEPAGE_SUCCESS;
    }

    spin_lock_irq(&mapping->tree_lock);
    @@ -399,7 +399,7 @@ int migrate_huge_page_move_mapping(struct address_space *mapping,
    page_unfreeze_refs(page, expected_count - 1);

    spin_unlock_irq(&mapping->tree_lock);
    - return 0;
    + return MIGRATEPAGE_SUCCESS;
    }

    /*
    @@ -486,11 +486,11 @@ int migrate_page(struct address_space *mapping,

    rc = migrate_page_move_mapping(mapping, newpage, page, NULL, mode);

    - if (rc)
    + if (rc != MIGRATEPAGE_SUCCESS)
    return rc;

    migrate_page_copy(newpage, page);
    - return 0;
    + return MIGRATEPAGE_SUCCESS;
    }
    EXPORT_SYMBOL(migrate_page);

    @@ -513,7 +513,7 @@ int buffer_migrate_page(struct address_space *mapping,

    rc = migrate_page_move_mapping(mapping, newpage, page, head, mode);

    - if (rc)
    + if (rc != MIGRATEPAGE_SUCCESS)
    return rc;

    /*
    @@ -549,7 +549,7 @@ int buffer_migrate_page(struct address_space *mapping,

    } while (bh != head);

    - return 0;
    + return MIGRATEPAGE_SUCCESS;
    }
    EXPORT_SYMBOL(buffer_migrate_page);
    #endif
    @@ -814,7 +814,7 @@ skip_unmap:
    put_anon_vma(anon_vma);

    uncharge:
    - mem_cgroup_end_migration(mem, page, newpage, rc == 0);
    + mem_cgroup_end_migration(mem, page, newpage, rc == MIGRATEPAGE_SUCCESS);
    unlock:
    unlock_page(page);
    out:
    @@ -987,7 +987,7 @@ int migrate_pages(struct list_head *from,
    case -EAGAIN:
    retry++;
    break;
    - case 0:
    + case MIGRATEPAGE_SUCCESS:
    break;
    default:
    /* Permanent failure */
    @@ -1024,7 +1024,7 @@ int migrate_huge_page(struct page *hpage, new_page_t get_new_page,
    /* try again */
    cond_resched();
    break;
    - case 0:
    + case MIGRATEPAGE_SUCCESS:
    goto out;
    default:
    rc = -EIO;
    --
    1.7.11.7


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