Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751536AbaK2KIr (ORCPT ); Sat, 29 Nov 2014 05:08:47 -0500 Received: from smtp2-g21.free.fr ([212.27.42.2]:28605 "EHLO smtp2-g21.free.fr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751385AbaK2KIp (ORCPT ); Sat, 29 Nov 2014 05:08:45 -0500 Date: Sat, 29 Nov 2014 11:08:33 +0100 From: Sabrina Dubroca To: Stephen Rothwell Cc: Jens Axboe , "Theodore Ts'o" , linux-next@vger.kernel.org, linux-kernel@vger.kernel.org, Tejun Heo , Jeremiah Mahler Subject: Re: linux-next: manual merge of the block tree with the ext4 tree Message-ID: <20141129100833.GA31892@kria> References: <20141127145347.0083c0bc@canb.auug.org.au> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20141127145347.0083c0bc@canb.auug.org.au> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, [adding Jeremiah Mahler to CC] 2014-11-27, 14:53:47 +1100, Stephen Rothwell wrote: > Hi Jens, > > Today's linux-next merge of the block tree got a conflict in > fs/fs-writeback.c between commit ef7fdf5e8c87 ("vfs: add support for a > lazytime mount option") from the ext4 tree and commit 9c6ac78eb352 > ("writeback: fix a subtle race condition in I_DIRTY clearing") from the > block tree. > > I fixed it up (I took a guess, plese check - see below) and can carry > the fix as necessary (no action is required). > > -- > Cheers, > Stephen Rothwell sfr@canb.auug.org.au > > diff --cc fs/fs-writeback.c > index 3d87174408ae,2d609a5fbfea..000000000000 > --- a/fs/fs-writeback.c > +++ b/fs/fs-writeback.c > @@@ -482,14 -479,30 +482,30 @@@ __writeback_single_inode(struct inode * > * write_inode() > */ > spin_lock(&inode->i_lock); > - /* Clear I_DIRTY_PAGES if we've written out all dirty pages */ > - if (!mapping_tagged(mapping, PAGECACHE_TAG_DIRTY)) > - inode->i_state &= ~I_DIRTY_PAGES; > + > - dirty = inode->i_state & I_DIRTY; > - inode->i_state &= ~I_DIRTY; > + dirty = inode->i_state & I_DIRTY_INODE; > + inode->i_state &= ~I_DIRTY_INODE; > + > + /* > + * Paired with smp_mb() in __mark_inode_dirty(). This allows > + * __mark_inode_dirty() to test i_state without grabbing i_lock - > + * either they see the I_DIRTY bits cleared or we see the dirtied > + * inode. > + * > + * I_DIRTY_PAGES is always cleared together above even if @mapping > + * still has dirty pages. The flag is reinstated after smp_mb() if > + * necessary. This guarantees that either __mark_inode_dirty() > + * sees clear I_DIRTY_PAGES or we see PAGECACHE_TAG_DIRTY. > + */ > + smp_mb(); > + > + if (mapping_tagged(mapping, PAGECACHE_TAG_DIRTY)) > + inode->i_state |= I_DIRTY_PAGES; > + > spin_unlock(&inode->i_lock); > + > /* Don't write the inode if only I_DIRTY_PAGES was set */ > - if (dirty & (I_DIRTY_SYNC | I_DIRTY_DATASYNC)) { > + if (dirty) { > int err = write_inode(inode, wbc); > if (ret == 0) > ret = err; I think there's a problem in your fix, Stephen. I'm getting hangs at boot (strangely -- in QEMU -- only when booting via grub, not when using -kernel) and during shutdown. Jeremiah seems to have the same problem and his bisection led to the merge commit: https://lkml.org/lkml/2014/11/29/17 The following solves both issues for me. I think it makes sense given the #defines from ef7fdf5e8c87, since Tejun intended to clear I_DIRTY_PAGES. diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c index b70e45f45afa..6b2510d97a0a 100644 --- a/fs/fs-writeback.c +++ b/fs/fs-writeback.c @@ -484,7 +484,7 @@ __writeback_single_inode(struct inode *inode, struct writeback_control *wbc) spin_lock(&inode->i_lock); dirty = inode->i_state & I_DIRTY_INODE; - inode->i_state &= ~I_DIRTY_INODE; + inode->i_state &= ~I_DIRTY; /* * Paired with smp_mb() in __mark_inode_dirty(). This allows -- Thanks, Sabrina -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/