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SubjectRe: [PATCH 2/2] mm: Make swap_readpage() for SWP_FS_OPS use ->direct_IO() not ->readpage()
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David Howells <dhowells@redhat.com> wrote:

> Matthew Wilcox <willy@infradead.org> wrote:
>
> > After submitting the IO here ...
> >
> > > + if (ret != -EIOCBQUEUED)
> > > + swapfile_read_complete(&ki->iocb, ret, 0);
> >
> > We only touch the 'ki' here ... if the caller didn't call read_complete
> >
> > > + swapfile_put_kiocb(ki);
> >
> > Except for here, which is only touched in order to put the refcount.
> >
> > So why can't swapfile_read_complete() do the work of freeing the ki?
>
> When I was doing something similar for cachefiles, I couldn't get it to work
> like that. I'll have another look at that.

Ah, yes. generic_file_direct_write() accesses in the kiocb *after* calling
->direct_IO(), so the kiocb *must not* go away until after
generic_file_direct_write() has returned.

David

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