Re: [bisected commit 0fc9d10] NFS-server corruption with 3.4

[Konstantin Khlebnikov]

Hans de Bruin wrote:
> On 06/05/2012 06:39 PM, Konstantin Khlebnikov wrote:
> > OGAWA Hirofumi wrote:
> > > Konstantin Khlebnikov<khlebnikov@xxxxxxxxxx>  writes:
> > >
> > > > Proper fix in attachment.
> > >
> > > Maybe, you are going to add the stable tag for next stable?
> > >
> > > Thanks.
> >
> > Yes, this definitely must be in next stable 3.4.x , but first I'll wait
> > for confirmation.
> >
> > Guys, who can reproduce this, please check patch "radix-tree: fix
> > contiguous iterator"
> > from my previous mail in this thread.
> >
> > > > radix-tree: fix contiguous iterator
> > > >
> > > > From: Konstantin Khlebnikov<khlebnikov@xxxxxxxxxx>
> > > >
> > > > This patch fixes bug in macro radix_tree_for_each_contig().
> > > > If radix_tree_next_slot() sees NULL in next slot it returns NULL, but
> > > > following
> > > > radix_tree_next_chunk() switches iterating into next chunk. As result
> > > > iterating
> > > > becomes non-contiguous and breaks vfs "splice" and all its users.
>
> I patched on to off v3.4 and Firefox an Thunderbird do not segfault
> anymore. The do not start either. This was de feature on my 'production'
> server I could not reproduce on my test server. Maybe it has something
> to with the different type of nic's.
>
> For the second attempt I branched of at 0fc9d1040313047edf6a39fd and
> applied your patch on top of it. Firefox an Thunderbird where back
> again. So your patch works.
>
> Now I need some git-instructions. Apparently something else is broken. I
> branched of with:
>
> git branch debug 0fc9d1040313047edf6a3
> git checkout debug
> applied the patch.
> git commit -a (got commit 5c09c685ba2d36c3b905220d43ad1b47354e456eed back)
>
> Now I want all commits in my master branch up until ref v3.4 added to my
> debug branch so I can bisect between 5c09 and v3.4

No, it does not work in this way. you should apply patch before each test.
You can fix radix-tree bug in find_get_pages_contig() to avoid changing
radix-tree.h and rebuild kernel faster.

--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -927,7 +927,7 @@ repeat:
                 * otherwise we can get both false positives and false
                 * negatives, which is just confusing to the caller.
                 */
-               if (page->mapping == NULL || page->index != iter.index) {
+               if (page->mapping == NULL || page->index != index + ret) {
                        page_cache_release(page);
                        break;
                }

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