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    Subject[PATCHv4 21/39] thp, libfs: initial support of thp in simple_read/write_begin/write_end
    Date
    From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>

    For now we try to grab a huge cache page if gfp_mask has __GFP_COMP.
    It's probably to weak condition and need to be reworked later.

    Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
    ---
    fs/libfs.c | 50 ++++++++++++++++++++++++++++++++++++-----------
    include/linux/pagemap.h | 8 ++++++++
    2 files changed, 47 insertions(+), 11 deletions(-)

    diff --git a/fs/libfs.c b/fs/libfs.c
    index 916da8c..ce807fe 100644
    --- a/fs/libfs.c
    +++ b/fs/libfs.c
    @@ -383,7 +383,7 @@ EXPORT_SYMBOL(simple_setattr);

    int simple_readpage(struct file *file, struct page *page)
    {
    - clear_highpage(page);
    + clear_pagecache_page(page);
    flush_dcache_page(page);
    SetPageUptodate(page);
    unlock_page(page);
    @@ -394,21 +394,44 @@ int simple_write_begin(struct file *file, struct address_space *mapping,
    loff_t pos, unsigned len, unsigned flags,
    struct page **pagep, void **fsdata)
    {
    - struct page *page;
    + struct page *page = NULL;
    pgoff_t index;

    index = pos >> PAGE_CACHE_SHIFT;

    - page = grab_cache_page_write_begin(mapping, index, flags);
    + /* XXX: too weak condition? */
    + if (mapping_can_have_hugepages(mapping)) {
    + page = grab_cache_page_write_begin(mapping,
    + index & ~HPAGE_CACHE_INDEX_MASK,
    + flags | AOP_FLAG_TRANSHUGE);
    + /* fallback to small page */
    + if (!page) {
    + unsigned long offset;
    + offset = pos & ~PAGE_CACHE_MASK;
    + len = min_t(unsigned long,
    + len, PAGE_CACHE_SIZE - offset);
    + }
    + BUG_ON(page && !PageTransHuge(page));
    + }
    + if (!page)
    + page = grab_cache_page_write_begin(mapping, index, flags);
    if (!page)
    return -ENOMEM;
    -
    *pagep = page;

    - if (!PageUptodate(page) && (len != PAGE_CACHE_SIZE)) {
    - unsigned from = pos & (PAGE_CACHE_SIZE - 1);
    -
    - zero_user_segments(page, 0, from, from + len, PAGE_CACHE_SIZE);
    + if (!PageUptodate(page)) {
    + unsigned from;
    +
    + if (PageTransHuge(page) && len != HPAGE_PMD_SIZE) {
    + from = pos & ~HPAGE_PMD_MASK;
    + zero_huge_user_segment(page, 0, from);
    + zero_huge_user_segment(page,
    + from + len, HPAGE_PMD_SIZE);
    + } else if (len != PAGE_CACHE_SIZE) {
    + from = pos & ~PAGE_CACHE_MASK;
    + zero_user_segments(page, 0, from,
    + from + len, PAGE_CACHE_SIZE);
    + }
    }
    return 0;
    }
    @@ -443,9 +466,14 @@ int simple_write_end(struct file *file, struct address_space *mapping,

    /* zero the stale part of the page if we did a short copy */
    if (copied < len) {
    - unsigned from = pos & (PAGE_CACHE_SIZE - 1);
    -
    - zero_user(page, from + copied, len - copied);
    + unsigned from;
    + if (PageTransHuge(page)) {
    + from = pos & ~HPAGE_PMD_MASK;
    + zero_huge_user(page, from + copied, len - copied);
    + } else {
    + from = pos & ~PAGE_CACHE_MASK;
    + zero_user(page, from + copied, len - copied);
    + }
    }

    if (!PageUptodate(page))
    diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
    index 8feeecc..462fcca 100644
    --- a/include/linux/pagemap.h
    +++ b/include/linux/pagemap.h
    @@ -579,4 +579,12 @@ static inline int add_to_page_cache(struct page *page,
    return error;
    }

    +static inline void clear_pagecache_page(struct page *page)
    +{
    + if (PageTransHuge(page))
    + zero_huge_user(page, 0, HPAGE_PMD_SIZE);
    + else
    + clear_highpage(page);
    +}
    +
    #endif /* _LINUX_PAGEMAP_H */
    --
    1.7.10.4


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