From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Mon, 22 Oct 2007 21:16:17 +0100 (BST) From: Hugh Dickins Subject: Re: msync(2) bug(?), returns AOP_WRITEPAGE_ACTIVATE to userland In-Reply-To: <84144f020710150447o94b1babo8b6e6a647828465f@mail.gmail.com> Message-ID: References: <200710142232.l9EMW8kK029572@agora.fsl.cs.sunysb.edu> <84144f020710150447o94b1babo8b6e6a647828465f@mail.gmail.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org Return-Path: To: Pekka Enberg Cc: Erez Zadok , Ryan Finnie , Andrew Morton , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, cjwatson@ubuntu.com, linux-mm@kvack.org List-ID: On Mon, 15 Oct 2007, Pekka Enberg wrote: > > I wonder whether _not setting_ BDI_CAP_NO_WRITEBACK implies that > ->writepage() will never return AOP_WRITEPAGE_ACTIVATE for > !wbc->for_reclaim case which would explain why we haven't hit this bug > before. Hugh, Andrew? Only ramdisk and shmem have been returning AOP_WRITEPAGE_ACTIVATE. Both of those set BDI_CAP_NO_WRITEBACK. ramdisk never returned it if !wbc->for_reclaim. I contend that shmem shouldn't either: it's a special code to get the LRU rotation right, not useful elsewhere. Though Documentation/filesystems/vfs.txt does imply wider use. I think this is where people use the phrase "go figure" ;) Hugh -- 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: email@kvack.org