From: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
To: Oleg Nesterov <oleg@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>,
Peter Zijlstra <peterz@infradead.org>,
Ananth N Mavinakayanahalli <ananth@in.ibm.com>,
Anton Arapov <anton@redhat.com>, Hugh Dickins <hughd@google.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 2/5] uprobes: __replace_page() should not use page_address_in_vma()
Date: Mon, 9 Jul 2012 15:58:37 +0530 [thread overview]
Message-ID: <20120709102837.GC32393@linux.vnet.ibm.com> (raw)
In-Reply-To: <20120706161857.GA9218@redhat.com>
> ------------------------------------------------------------------------------
> Subject: [PATCH v2 2/5] uprobes: __replace_page() should not use page_address_in_vma()
>
> page_address_in_vma(old_page) in __replace_page() is ugly and wrong.
> The caller already knows the correct virtual address, this page was
> found by get_user_pages(vaddr).
>
> However, page_address_in_vma() can actually fail if page->mapping was
> cleared by __delete_from_page_cache() after get_user_pages() returns.
> But this means the race with page reclaim, write_opcode() should not
> fail, it should retry and read this page again. Probably the race with
> remove_mapping() is not possible due to page_freeze_refs() logic, but
> afaics at least shmem_writepage()->shmem_delete_from_page_cache() can
> clear ->mapping.
>
> We could change __replace_page() to return -EAGAIN in this case, but
> it would be better to simply use the caller's vaddr and rely on
> page_check_address().
>
> Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
next prev parent reply other threads:[~2012-07-09 10:29 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-06-24 14:59 [PATCH v2 0/5] uprobes: write_opcode() cleanups Oleg Nesterov
2012-06-24 15:00 ` [PATCH v2 1/5] uprobes: don't recheck vma/f_mapping in write_opcode() Oleg Nesterov
2012-07-09 10:30 ` Srikar Dronamraju
2012-06-24 15:00 ` [PATCH v2 2/5] uprobes: __replace_page() should not use page_address_in_vma() Oleg Nesterov
2012-07-06 16:18 ` Oleg Nesterov
2012-07-09 10:28 ` Srikar Dronamraju [this message]
2012-06-24 15:00 ` [PATCH v2 3/5] uprobes: kill write_opcode()->lock_page(new_page) Oleg Nesterov
2012-07-09 10:29 ` Srikar Dronamraju
2012-06-24 15:00 ` [PATCH v2 4/5] uprobes: cleanup and document write_opcode()->lock_page(old_page) Oleg Nesterov
2012-07-09 10:29 ` Srikar Dronamraju
2012-06-24 15:01 ` [PATCH v2 5/5] uprobes: __replace_page() needs munlock_vma_page() Oleg Nesterov
2012-06-26 11:55 ` Anton Arapov
2012-06-26 15:47 ` Oleg Nesterov
2012-07-06 10:54 ` [PATCH v2 0/5] uprobes: write_opcode() cleanups Ingo Molnar
2012-07-06 16:07 ` Oleg Nesterov
2012-07-06 16:13 ` Oleg Nesterov
2012-07-09 9:12 ` Ingo Molnar
2012-07-09 13:30 ` Oleg Nesterov
2012-07-09 10:27 ` Srikar Dronamraju
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