From: Mingming Subject: Re: [PATCH] ext4: Fix delalloc sync hang with journal lock inversion Date: Thu, 22 May 2008 12:26:10 -0700 Message-ID: <1211484370.8596.46.camel@BVR-FS.beaverton.ibm.com> References: <1211391859-17399-1-git-send-email-aneesh.kumar@linux.vnet.ibm.com> <1211391859-17399-2-git-send-email-aneesh.kumar@linux.vnet.ibm.com> <1211391859-17399-3-git-send-email-aneesh.kumar@linux.vnet.ibm.com> <1211391859-17399-4-git-send-email-aneesh.kumar@linux.vnet.ibm.com> <1211479817.8596.42.camel@BVR-FS.beaverton.ibm.com> <20080522182653.GB7404@skywalker> Mime-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit Cc: tytso@mit.edu, sandeen@redhat.com, linux-ext4@vger.kernel.org To: "Aneesh Kumar K.V" Return-path: Received: from e2.ny.us.ibm.com ([32.97.182.142]:55902 "EHLO e2.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754027AbYEVT0a (ORCPT ); Thu, 22 May 2008 15:26:30 -0400 Received: from d03relay04.boulder.ibm.com (d03relay04.boulder.ibm.com [9.17.195.106]) by e2.ny.us.ibm.com (8.13.8/8.13.8) with ESMTP id m4MJQMmp019601 for ; Thu, 22 May 2008 15:26:22 -0400 Received: from d03av03.boulder.ibm.com (d03av03.boulder.ibm.com [9.17.195.169]) by d03relay04.boulder.ibm.com (8.13.8/8.13.8/NCO v8.7) with ESMTP id m4MJQB3S100788 for ; Thu, 22 May 2008 13:26:11 -0600 Received: from d03av03.boulder.ibm.com (loopback [127.0.0.1]) by d03av03.boulder.ibm.com (8.12.11.20060308/8.13.3) with ESMTP id m4MJQA6b028606 for ; Thu, 22 May 2008 13:26:11 -0600 In-Reply-To: <20080522182653.GB7404@skywalker> Sender: linux-ext4-owner@vger.kernel.org List-ID: On Thu, 2008-05-22 at 23:56 +0530, Aneesh Kumar K.V wrote: > On Thu, May 22, 2008 at 11:10:17AM -0700, Mingming wrote: > > > > On Wed, 2008-05-21 at 23:14 +0530, Aneesh Kumar K.V wrote: > > > Signed-off-by: Aneesh Kumar K.V > > > --- > > > fs/ext4/inode.c | 10 +++++++--- > > > 1 files changed, 7 insertions(+), 3 deletions(-) > > > > > > diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c > > > index 46cc610..076d00f 100644 > > > --- a/fs/ext4/inode.c > > > +++ b/fs/ext4/inode.c > > > @@ -1571,13 +1571,17 @@ static int ext4_da_writepages(struct address_space *mapping, > > > */ > > > if (wbc->nr_to_write > EXT4_MAX_WRITEBACK_PAGES) > > > wbc->nr_to_write = EXT4_MAX_WRITEBACK_PAGES; > > > - to_write -= wbc->nr_to_write; > > > > > > + to_write -= wbc->nr_to_write; > > > ret = mpage_da_writepages(mapping, wbc, ext4_da_get_block_write); > > > ext4_journal_stop(handle); > > > - to_write +=wbc->nr_to_write; > > > + if (wbc->nr_to_write) { > > > + /* We failed to write what we requested for */ > > > + to_write += wbc->nr_to_write; > > > + break; > > > + } > > > > Not sure about the break here... > > > + wbc->nr_to_write = to_write; > > > > Looks right. thanks. > > > > > } > > > - > > > out_writepages: > > > wbc->nr_to_write = to_write; > > > wbc->range_cyclic = range_cyclic; > > > > The call chain that made me look at this was > > #0 ext4_da_writepages (mapping=0xc76dc244, wbc=0xc790bf70) at fs/ext4/inode.c:1557 > #1 0xc0150176 in do_writepages (mapping=0xc76dc244, wbc=0xc790bf70) at mm/page-writeback.c:1004 > #2 0xc0180fe6 in __writeback_single_inode (inode=0xc76dc11c, wbc=0xc790bf70) at fs/fs-writeback.c:285 > #3 0xc018146c in sync_sb_inodes (sb=0xc7abac00, wbc=0xc790bf70) at fs/fs-writeback.c:502 > #4 0xc0181701 in writeback_inodes (wbc=0xc790bf70) at fs/fs-writeback.c:570 > #5 0xc01509f8 in background_writeout (_min_pages=) at mm/page-writeback.c:639 > #6 0xc0150f57 in pdflush (dummy=) at mm/pdflush.c:127 > #7 0xc01324af in kthread (_create=) at kernel/kthread.c:79 > #8 0xc0104633 in kernel_thread_helper () at include/asm/string_32.h:238 > > ext4_da_writepages gets called with nr_to_write MAX_WRITEBACK_PAGES. the > file size is only 4K. ie there is only one page to write. With these > value we get stuck in the above loop because to_write will never decrement > below 1023. > Ah, So I guess the comment should be reflect that the nr_to_write returned after mpage_da_writepages() means there is no more dirty page need to flush, then quit the loop. Mingming > > -aneesh