[Cluster-devel] [PATCH] mm: Avoid returning VM_FAULT_RETRY from ->page_mkwrite handlers

Andrew Morton akpm at linux-foundation.org
Fri Feb 3 23:20:54 UTC 2017


On Fri,  3 Feb 2017 16:07:29 +0100 Jan Kara <jack at suse.cz> wrote:

> Some ->page_mkwrite handlers may return VM_FAULT_RETRY as its return
> code (GFS2 or Lustre can definitely do this). However VM_FAULT_RETRY
> from ->page_mkwrite is completely unhandled by the mm code and results
> in locking and writeably mapping the page which definitely is not what
> the caller wanted. Fix Lustre and block_page_mkwrite_ret() used by other
> filesystems (notably GFS2) to return VM_FAULT_NOPAGE instead which
> results in bailing out from the fault code, the CPU then retries the
> access, and we fault again effectively doing what the handler wanted.

I'm not getting any sense of the urgency of this fix.  The bug *sounds*
bad?  Which kernel versions need fixing?




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