Messages in this thread | | | Date | Mon, 18 Dec 2006 22:53:43 +0000 | From | Christoph Hellwig <> | Subject | Re: bio pages with zero page reference count |
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On Mon, Dec 18, 2006 at 05:21:09PM -0500, Ed L. Cashin wrote: > (This email is a followup to "Re: [PATCH 2.6.19.1] fix aoe without > scatter-gather [Bug 7662]".) > > On Mon, Dec 18, 2006 at 12:53:00PM -0500, Ed L. Cashin wrote: > ... > > This patch eliminates the offset data on cards that don't support > > scatter-gather or have had scatter-gather turned off. There remains > > an unrelated issue that I'll address in a separate email. > > After fixing the problem with the skb headers, we noticed that there > were still problems when scatter gather wasn't in use. XFS was giving > us bios that had pages with a reference count of zero. > > The aoe driver sets up the skb with the frags pointing to the pages, > and when scatter gather isn't supported and __pskb_pull_tail gets > involved, put_page is called after the data is copied from the pages. > That causes problems because of the zero page reference count. > > It seems like it would always be incorrect for one part of the kernel > to give pages with a zero reference count to another part of the > kernel, so this seems like a bug in XFS. > > Christoph Hellwig, though, points out, > > > It's a kmalloced page. The same can happen with ext3 aswell, but > > only when doing log recovery. The last time this came up (vs > > iscsi) the conclusion was that the driver needs to handle this > > case. > > In attempting to find the conversation he was referencing, I only > found this: > > Subject: tcp_sendpage and page allocation lifetime vs. iscsi > Date: 2005-04-25 17:02:59 GMT > http://article.gmane.org/gmane.linux.kernel/298377 > > If anyone has a better reference, I'd like to see it.
I searched around a little bit and found these:
http://groups.google.at/group/open-iscsi/browse_frm/thread/17fbe253cf1f69dd/f26cf19b0fee9147?tvc=1&q=kmalloc+iscsi+%22christoph+hellwig%22&hl=de#f26cf19b0fee9147 http://www.ussg.iu.edu/hypermail/linux/kernel/0408.3/0061.html
But that's not the conclusion I was looking for. - 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/
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