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    Subject[PATCH 1/2] shmem: fix init_page_accessed use to stop !PageLRU bug
    Under shmem swapping load, I sometimes hit the VM_BUG_ON_PAGE(!PageLRU)
    in isolate_lru_pages() at mm/vmscan.c:1281!

    Commit 2457aec63745 ("mm: non-atomically mark page accessed during page
    cache allocation where possible") looks like interrupted work-in-progress.

    mm/filemap.c's call to init_page_accessed() is fine, but not mm/shmem.c's
    - shmem_write_begin() is clearly wrong to use it after shmem_getpage(),
    when the page is always visible in radix_tree, and often already on LRU.

    Revert change to shmem_write_begin(), and use init_page_accessed() or
    mark_page_accessed() appropriately for SGP_WRITE in shmem_getpage_gfp().

    SGP_WRITE also covers shmem_symlink(), which did not mark_page_accessed()
    before; but since many other filesystems use [__]page_symlink(), which did
    and does mark the page accessed, consider this as rectifying an oversight.

    Signed-off-by: Hugh Dickins <hughd@google.com>
    ---

    mm/shmem.c | 15 ++++++++++-----
    1 file changed, 10 insertions(+), 5 deletions(-)

    --- 3.16-rc3/mm/shmem.c 2014-06-29 15:22:10.592003936 -0700
    +++ linux/mm/shmem.c 2014-06-30 12:15:52.204093217 -0700
    @@ -1029,6 +1029,9 @@ repeat:
    goto failed;
    }

    + if (page && sgp == SGP_WRITE)
    + mark_page_accessed(page);
    +
    /* fallocated page? */
    if (page && !PageUptodate(page)) {
    if (sgp != SGP_READ)
    @@ -1110,6 +1113,9 @@ repeat:
    shmem_recalc_inode(inode);
    spin_unlock(&info->lock);

    + if (sgp == SGP_WRITE)
    + mark_page_accessed(page);
    +
    delete_from_swap_cache(page);
    set_page_dirty(page);
    swap_free(swap);
    @@ -1136,6 +1142,9 @@ repeat:

    __SetPageSwapBacked(page);
    __set_page_locked(page);
    + if (sgp == SGP_WRITE)
    + init_page_accessed(page);
    +
    error = mem_cgroup_charge_file(page, current->mm,
    gfp & GFP_RECLAIM_MASK);
    if (error)
    @@ -1412,13 +1421,9 @@ shmem_write_begin(struct file *file, str
    loff_t pos, unsigned len, unsigned flags,
    struct page **pagep, void **fsdata)
    {
    - int ret;
    struct inode *inode = mapping->host;
    pgoff_t index = pos >> PAGE_CACHE_SHIFT;
    - ret = shmem_getpage(inode, index, pagep, SGP_WRITE, NULL);
    - if (ret == 0 && *pagep)
    - init_page_accessed(*pagep);
    - return ret;
    + return shmem_getpage(inode, index, pagep, SGP_WRITE, NULL);
    }

    static int

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