osd fs: __r4w_get_page rely on PageUptodate for uptodate

Commit 42cb14b110a5 ("mm: migrate dirty page without
clear_page_dirty_for_io etc") simplified the migration of a PageDirty
pagecache page: one stat needs moving from zone to zone and that's about
all.

It's convenient and safest for it to shift the PageDirty bit from old
page to new, just before updating the zone stats: before copying data
and marking the new PageUptodate.  This is all done while both pages are
isolated and locked, just as before; and just as before, there's a
moment when the new page is visible in the radix_tree, but not yet
PageUptodate.  What's new is that it may now be briefly visible as
PageDirty before it is PageUptodate.

When I scoured the tree to see if this could cause a problem anywhere,
the only places I found were in two similar functions __r4w_get_page():
which look up a page with find_get_page() (not using page lock), then
claim it's uptodate if it's PageDirty or PageWriteback or PageUptodate.

I'm not sure whether that was right before, but now it might be wrong
(on rare occasions): only claim the page is uptodate if PageUptodate.
Or perhaps the page in question could never be migratable anyway?

Signed-off-by: Hugh Dickins <hughd@google.com>
Tested-by: Boaz Harrosh <ooo@electrozaur.com>
Cc: Benny Halevy <bhalevy@panasas.com>
Cc: Trond Myklebust <trond.myklebust@primarydata.com>
Cc: Christoph Lameter <cl@linux.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/exofs/inode.c b/fs/exofs/inode.c
index 73c64daa0f5517b4ff8271bd17e25740bb83d506..60f03b78914e3012e50c90a9e9069aff615467be 100644 (file)
--- a/fs/exofs/inode.c
+++ b/fs/exofs/inode.c
@@ -592,10 +592,7 @@ static struct page *__r4w_get_page(void *priv, u64 offset, bool *uptodate)
                        }
                        unlock_page(page);
                }
-               if (PageDirty(page) || PageWriteback(page))
-                       *uptodate = true;
-               else
-                       *uptodate = PageUptodate(page);
+               *uptodate = PageUptodate(page);
                EXOFS_DBGMSG2("index=0x%lx uptodate=%d\n", index, *uptodate);
                return page;
        } else {

diff --git a/fs/nfs/objlayout/objio_osd.c b/fs/nfs/objlayout/objio_osd.c
index 5c0c6b58157f906d6c35ce737a6d4a5623027bf1..9aebffb4050597e1daae74f28375d86335f73e0c 100644 (file)
--- a/fs/nfs/objlayout/objio_osd.c
+++ b/fs/nfs/objlayout/objio_osd.c
@@ -476,10 +476,7 @@ static struct page *__r4w_get_page(void *priv, u64 offset, bool *uptodate)
                }
                unlock_page(page);
        }
-       if (PageDirty(page) || PageWriteback(page))
-               *uptodate = true;
-       else
-               *uptodate = PageUptodate(page);
+       *uptodate = PageUptodate(page);
        dprintk("%s: index=0x%lx uptodate=%d\n", __func__, index, *uptodate);
        return page;
 }