Peter Zijlstra wrote:
On Thu, 2007-01-25 at 00:43 +1100, Nick Piggin wrote:
Have you seen the new launder_page() a_op? called from
invalidate_inode_pages2_range()
It would have been nice to make that one into a more potentially
useful generic callback.
That can still be done when the need arises, right?
Yeah I guess so.
But why was it introduced, exactly? I can't tell from the code or
the discussion why NFS couldn't start the IO, and signal the caller
to wait_on_page_writeback and retry? That seemed to me like the
convetional fix.
to quote a bit:
On Tue, 19 Dec 2006 18:19:38 -0500
Trond Myklebust <[email protected]> wrote:
NFS: Fix race in nfs_release_page()
invalidate_inode_pages2() may set the dirty bit on a page owing to the call
to unmap_mapping_range() after the page was locked. In order to fix this,
NFS has hooked the releasepage() method. This, however leads to deadlocks
in other parts of the VM.
and:
Now, arguably the VM shouldn't be calling try_to_release_page() with
__GFP_FS when it's holding a lock on a page.
But otoh, NFS should never be running lock_page() within nfs_release_page()
against the page which was passed into nfs_release_page(). It'll deadlock
for sure.
The reason why it is happening is that the last dirty page from that
inode gets cleaned, resulting in a call to dput().
OK but what's the problem with just failing to release the page if it
is dirty, I wonder? In the worst case, page reclaim will just end up
doing a writeout to clean it.
--
SUSE Labs, Novell Inc.
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