lkml.org 
[lkml]   [2012]   [Apr]   [17]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH 08/11] nfs: disable data cache revalidation for swapfiles
    > On Mon, Apr 16, 2012 at 9:44 AM, Mel Gorman <mgorman@suse.de> wrote:
    > > On Mon, Apr 16, 2012 at 09:10:04AM -0400, Fred Isaman wrote:
    > >> > <SNIP>
    > >> > -static struct nfs_page *nfs_page_find_request_locked(struct page *page)
    > >> > +static struct nfs_page *
    > >> > +nfs_page_find_request_locked(struct nfs_inode *nfsi, struct page *page)
    > >> >  {
    > >> >        struct nfs_page *req = NULL;
    > >> >
    > >> > -       if (PagePrivate(page)) {
    > >> > +       if (PagePrivate(page))
    > >> >                req = (struct nfs_page *)page_private(page);
    > >> > -               if (req != NULL)
    > >> > -                       kref_get(&req->wb_kref);
    > >> > +       else if (unlikely(PageSwapCache(page))) {
    > >> > +               struct nfs_page *freq, *t;
    > >> > +
    > >> > +               /* Linearly search the commit list for the correct req */
    > >> > +               list_for_each_entry_safe(freq, t, &nfsi->commit_list, wb_list) {
    > >> > +                       if (freq->wb_page == page) {
    > >> > +                               req = freq;
    > >> > +                               break;
    > >> > +                       }
    > >> > +               }
    > >> > +
    > >> > +               BUG_ON(req == NULL);
    > >>
    > >> I suspect I am missing something, but why is it guaranteed that the
    > >> req is on the commit list?
    > >>
    > >
    > > It's a fair question and a statement about what I expected to happen.
    > > The commit list replaces the nfs_page_tree radix tree that used to exist
    > > and my understanding was that the req would exist in the radix tree until
    > > the swap IO was completed. I expected it to be the same for the commit
    > > list and the BUG_ON was based on that expectation. Are there cases where
    > > the req would not be found?
    > >
    >
    > A req is on the commit list only if it actually needs to be scheduled
    > for COMMIT. In other words, only after it has been sent via WRITE and
    > the server did not return NFS_FILE_SYNC.
    >
    > Thus dirtying a page, then trying to touch it again before the WRITE
    > is sent will not find the corresponding req on the commit_list.

    Thanks for the explanation. I'll remove the BUG_ON

    --
    Mel Gorman
    SUSE Labs
    --
    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to majordomo@vger.kernel.org
    More majordomo info at http://vger.kernel.org/majordomo-info.html
    Please read the FAQ at http://www.tux.org/lkml/

    \
     
     \ /
      Last update: 2012-04-17 14:43    [W:3.292 / U:1.384 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site