lkml.org 
[lkml]   [2014]   [Dec]   [2]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [patch 3/3] mm: memory: merge shared-writable dirtying branches in do_wp_page()
    On Mon 01-12-14 17:58:02, Johannes Weiner wrote:
    > Whether there is a vm_ops->page_mkwrite or not, the page dirtying is
    > pretty much the same. Make sure the page references are the same in
    > both cases, then merge the two branches.
    >
    > It's tempting to go even further and page-lock the !page_mkwrite case,
    > to get it in line with everybody else setting the page table and thus
    > further simplify the model. But that's not quite compelling enough to
    > justify dropping the pte lock, then relocking and verifying the entry
    > for filesystems without ->page_mkwrite, which notably includes tmpfs.
    > Leave it for now and lock the page late in the !page_mkwrite case.
    >
    > Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
    > ---
    > mm/memory.c | 46 ++++++++++++++++------------------------------
    > 1 file changed, 16 insertions(+), 30 deletions(-)
    >
    > diff --git a/mm/memory.c b/mm/memory.c
    > index 2a2e3648ed65..ff92abfa5303 100644
    > --- a/mm/memory.c
    > +++ b/mm/memory.c
    ...
    > @@ -2147,42 +2147,28 @@ reuse:
    > pte_unmap_unlock(page_table, ptl);
    > ret |= VM_FAULT_WRITE;
    >
    > - if (!dirty_page)
    > - return ret;
    > -
    > - if (!page_mkwrite) {
    > + if (dirty_shared) {
    > struct address_space *mapping;
    > int dirtied;
    >
    > - lock_page(dirty_page);
    > - dirtied = set_page_dirty(dirty_page);
    > - mapping = dirty_page->mapping;
    > - unlock_page(dirty_page);
    > + if (!page_mkwrite)
    > + lock_page(old_page);
    >
    > - if (dirtied && mapping) {
    > - /*
    > - * Some device drivers do not set page.mapping
    > - * but still dirty their pages
    > - */
    > - balance_dirty_pages_ratelimited(mapping);
    > - }
    > + dirtied = set_page_dirty(old_page);
    > + mapping = old_page->mapping;
    > + unlock_page(old_page);
    > + page_cache_release(old_page);
    >
    > - file_update_time(vma->vm_file);
    > - }
    > - put_page(dirty_page);
    > - if (page_mkwrite) {
    > - struct address_space *mapping = dirty_page->mapping;
    > -
    > - set_page_dirty(dirty_page);
    > - unlock_page(dirty_page);
    > - page_cache_release(dirty_page);
    > - if (mapping) {
    > + if ((dirtied || page_mkwrite) && mapping) {
    Why do we actually call balance_dirty_pages_ratelimited() even if we
    didn't dirty the page when ->page_mkwrite() exists? Is it because
    filesystem may dirty the page in ->page_mkwrite() and we don't want it to
    deal with calling balance_dirty_pages_ratelimited()?

    Otherwise the patch looks good to me.

    Honza

    > /*
    > * Some device drivers do not set page.mapping
    > * but still dirty their pages
    > */
    > balance_dirty_pages_ratelimited(mapping);
    > }
    > +
    > + if (!page_mkwrite)
    > + file_update_time(vma->vm_file);
    > }
    >
    > return ret;
    > --
    > 2.1.3
    >
    --
    Jan Kara <jack@suse.cz>
    SUSE Labs, CR


    \
     
     \ /
      Last update: 2014-12-02 11:01    [W:3.705 / U:0.684 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site