From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Fri, 24 Jun 2005 01:24:32 -0700 From: William Lee Irwin III Subject: Re: [patch][rfc] 5/5: core remove PageReserved Message-ID: <20050624082432.GF3334@holomorphy.com> References: <42BA5F37.6070405@yahoo.com.au> <42BA5F5C.3080101@yahoo.com.au> <42BA5F7B.30904@yahoo.com.au> <42BA5FA8.7080905@yahoo.com.au> <42BA5FC8.9020501@yahoo.com.au> <42BA5FE8.2060207@yahoo.com.au> <20050623095153.GB3334@holomorphy.com> <20050623215011.0b1e6ef2.akpm@osdl.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20050623215011.0b1e6ef2.akpm@osdl.org> Sender: owner-linux-mm@kvack.org Return-Path: To: Andrew Morton Cc: nickpiggin@yahoo.com.au, linux-kernel@vger.kernel.org, linux-mm@kvack.org, hugh@veritas.com, pbadari@us.ibm.com, linux-scsi@vger.kernel.org List-ID: William Lee Irwin III wrote: >> An answer should be devised for this. My numerous SCSI CD-ROM devices >> (I have 5 across several different machines of several different arches) >> are rather unlikely to be happy with /* FIXME: XXX ... as an answer. [...] >> Mutatis mutandis for my SCSI tape drive. On Thu, Jun 23, 2005 at 09:50:11PM -0700, Andrew Morton wrote: > This scsi code is already rather wrong. There isn't much point in just > setting PG_dirty and leaving the page marked as clean in the radix tree. > As it is we'll lose data if the user reads it into a MAP_SHARED memory > buffer. > set_page_dirty_lock() should be used here. That can sleep. > The above two functions are called under write_lock_irqsave() (at least) > and might be called from irq context (dunno). So we cannot use > set_page_dirty_lock() and we don't have a ref on the page's inode. We > could use set_page_dirty() and be racy against page reclaim. > But to get all this correct (and it's very incorrect now) we'd need to punt > the page dirtying up to process context, along the lines of > bio_check_pages_dirty(). > Or, if st_unmap_user_pages() and sgl_unmap_user_pages() are not called from > irq context then we should arrange for them to be called without locks held > and use set_page_dirty_lock(). This all sounds very reasonable. I was originally more concerned about the new FIXME getting introduced but this sounds like a good way to resolve the preexisting FIXME's surrounding all this. -- wli -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: aart@kvack.org