Re: [PATCH 2/4] AFS: Add a function to excise a rejected write from the pagecache
- From: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
- Date: Thu, 24 May 2007 16:24:47 -0700
On Fri, 25 May 2007 00:08:43 +0100
David Howells <dhowells@xxxxxxxxxx> wrote:
Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote:
hm. I don't see why that race window would be a problem in practice: the
page-exciser does a lock_page();wait_on_page_writeback() as normal, then
proceeds with its business?
No. The page-exciser ends (cancels) PG_writeback, not waits for it (something
has to clear the flag). The problem is that the truncation routines may be
sat there holding a lock on the page whilst waiting for PG_writeback to go
away - so we have to clear PG_writeback before we can think about getting
PG_lock:-(
But we already covered that? Your exciser can do an unconditional
end_page_writeback(), because it is this thread of control which did the
set_page_writeback(). So we end up with:
end_page_writeback(page);
lock_page(page);
wait_on_page_writeback(page);
<now nail it>
But given that this doesn't work right for some reason, can we use PG_error
and then handle that appropriately in the filesystem's ->prepare_write() and
->page_mkwrite()?
Possibly, though I'd rather they didn't see such a page.
Well someone needs to be taught all about this case. Question is, should
it be the VFS, or should it just be the address_space(s) which brought
this state about, and which care about it?
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- References:
- Re: [PATCH 2/4] AFS: Add a function to excise a rejected write from the pagecache
- From: Andrew Morton
- Re: [PATCH 2/4] AFS: Add a function to excise a rejected write from the pagecache
- From: Andrew Morton
- Re: [PATCH 2/4] AFS: Add a function to excise a rejected write from the pagecache
- From: Andrew Morton
- [PATCH 1/4] AFS: Add TestSetPageError()
- From: David Howells
- [PATCH 2/4] AFS: Add a function to excise a rejected write from the pagecache
- From: David Howells
- Re: [PATCH 2/4] AFS: Add a function to excise a rejected write from the pagecache
- From: David Howells
- Re: [PATCH 2/4] AFS: Add a function to excise a rejected write from the pagecache
- From: David Howells
- Re: [PATCH 2/4] AFS: Add a function to excise a rejected write from the pagecache
- From: David Howells
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