From mboxrd@z Thu Jan 1 00:00:00 1970 Subject: Re: NR_UNSTABLE_FS vs. NR_FILE_DIRTY: double counting pages? From: Trond Myklebust In-Reply-To: <4632A1A6.90702@google.com> References: <4632A1A6.90702@google.com> Content-Type: text/plain Date: Sun, 29 Apr 2007 16:22:15 -0400 Message-Id: <1177878135.6400.37.camel@heimdal.trondhjem.org> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Ethan Solomita Cc: LKML , linux-mm@kvack.org List-ID: On Fri, 2007-04-27 at 18:21 -0700, Ethan Solomita wrote: > There are several places where we add together NR_UNSTABLE_FS and > NF_FILE_DIRTY: > > sync_inodes_sb() > balance_dirty_pages() > wakeup_pdflush() > wb_kupdate() > prefetch_suitable() > > I can trace a standard codepath where it seems both of these are set > on the same page: > > nfs_file_aops.commit_write -> > nfs_commit_write > nfs_updatepages > nfs_writepage_setup > nfs_wb_page > nfs_wb_page_priority > nfs_writepage_locked > nfs_flush_mapping > nfs_flush_list > nfs_flush_multi > nfs_write_partial_ops.rpc_call_done > nfs_writeback_done_partial > nfs_writepage_release > nfs_reschedule_unstable_write > nfs_mark_request_commit > incr NR_UNSTABLE_NFS > > nfs_file_aops.commit_write -> > nfs_commit_write > nfs_updatepage > __set_page_dirty_nobuffers > incr NF_FILE_DIRTY > > > This is the standard code path that derives from sys_write(). Can > someone either show how this code sequence can't happen, or confirm for > me that there's a bug? > -- Ethan It should not happen. If the page is on the unstable list, then it will be committed before nfs_updatepage is allowed to redirty it. See the recent fixes in 2.6.21-rc7. Trond -- 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