From: Andreas Dilger Subject: Re: [PATCH 4/6 v7] ext4: Lock i_mutex for punch hole Date: Wed, 31 Aug 2011 13:44:38 -0600 Message-ID: References: <1314750513-10045-1-git-send-email-achender@linux.vnet.ibm.com> <1314750513-10045-5-git-send-email-achender@linux.vnet.ibm.com> <7607E9C9-650E-4C7F-B5EA-1DD76E564C05@dilger.ca> <4E5E8224.3040607@linux.vnet.ibm.com> Mime-Version: 1.0 (Apple Message framework v1084) Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 8BIT Cc: linux-ext4@vger.kernel.org To: Allison Henderson Return-path: Received: from idcmail-mo1so.shaw.ca ([24.71.223.10]:58997 "EHLO idcmail-mo1so.shaw.ca" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752942Ab1HaTok convert rfc822-to-8bit (ORCPT ); Wed, 31 Aug 2011 15:44:40 -0400 In-Reply-To: <4E5E8224.3040607@linux.vnet.ibm.com> Sender: linux-ext4-owner@vger.kernel.org List-ID: On 2011-08-31, at 12:49 PM, Allison Henderson wrote: > On 08/30/2011 05:31 PM, Andreas Dilger wrote: >> On 2011-08-30, at 6:28 PM, Allison Henderson wrote: >>> This patch modifies the fallocate routine to lock i_mutex during >>> the punch hole operation. >>> >>> Yongqiang noticed that the vfs layer locks i_mutex for truncate, >>> but not fallocate, so the fallocate routine will need to take >>> care of locking i_mutex. Otherwise a page may be mapped after >>> punch hole has released the pages, but before i_data_sem is >>> locked to release the blocks in the extent tree. >> >> If the VFS is locking i_mutex for truncate, shouldn't the locking for >> fallocate() also be done in the VFS? > > Alrighty, I will do some poking around with this idea first. I dont know if other files systems are already locking i_mutex during fallocate, and it may be the case that not all filesystems need i_mutex locked for fallocate. So I'll do a little research first, but I will post back with what I find. Thx! Probably a good idea to bring up this issue on linux-fsdevel. >>> Signed-off-by: Allison Henderson >>> --- >>> :100644 100644 9124cd2... 007fb08... M fs/ext4/extents.c >>> fs/ext4/extents.c | 10 +++++++--- >>> 1 files changed, 7 insertions(+), 3 deletions(-) >>> >>> diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c >>> index 9124cd2..007fb08 100644 >>> --- a/fs/ext4/extents.c >>> +++ b/fs/ext4/extents.c >>> @@ -3774,8 +3774,13 @@ long ext4_fallocate(struct file *file, int mode, loff_t offset, loff_t len) >>> if (mode& ~(FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE)) >>> return -EOPNOTSUPP; >>> >>> - if (mode& FALLOC_FL_PUNCH_HOLE) >>> - return ext4_punch_hole(file, offset, len); >>> + mutex_lock(&inode->i_mutex); >>> + >>> + if (mode& FALLOC_FL_PUNCH_HOLE) { >>> + ret = ext4_punch_hole(file, offset, len); >>> + mutex_unlock(&inode->i_mutex); >>> + return ret; >>> + } >>> >>> trace_ext4_fallocate_enter(inode, offset, len, mode); >>> map.m_lblk = offset>> blkbits; >>> @@ -3789,7 +3794,6 @@ long ext4_fallocate(struct file *file, int mode, loff_t offset, loff_t len) >>> * credits to insert 1 extent into extent tree >>> */ >>> credits = ext4_chunk_trans_blocks(inode, max_blocks); >>> - mutex_lock(&inode->i_mutex); >>> ret = inode_newsize_ok(inode, (len + offset)); >>> if (ret) { >>> mutex_unlock(&inode->i_mutex); >>> -- >>> 1.7.1 >>> >>> -- >>> To unsubscribe from this list: send the line "unsubscribe linux-ext4" in >>> the body of a message to majordomo@vger.kernel.org >>> More majordomo info at http://vger.kernel.org/majordomo-info.html >> >> >> Cheers, Andreas >> >> >> >> >> > Cheers, Andreas