From: Jan Kara <jack@suse.cz>
To: Dmitry Monakhov <dmonakhov@openvz.org>
Cc: linux-ext4@vger.kernel.org, tytso@mit.edu, jack@suse.cz,
wenqing.lz@taobao.com
Subject: Re: [PATCH 5/7] ext4: serialize unlocked dio reads with truncate
Date: Mon, 10 Sep 2012 11:54:50 +0200 [thread overview]
Message-ID: <20120910095450.GG22903@quack.suse.cz> (raw)
In-Reply-To: <1347211634-11509-6-git-send-email-dmonakhov@openvz.org>
On Sun 09-09-12 21:27:12, Dmitry Monakhov wrote:
> Current serialization will works only for DIO which holds
> i_mutex, but nonlocked DIO following race is possible:
>
> dio_nolock_read_task truncate_task
> ->ext4_setattr()
> ->inode_dio_wait()
> ->ext4_ext_direct_IO
> ->ext4_ind_direct_IO
> ->__blockdev_direct_IO
> ->ext4_get_block
> ->truncate_setsize()
> ->ext4_truncate()
> #alloc truncated blocks
> #to other inode
> ->submit_io()
> #INFORMATION LEAK
>
> In order to serialize with unlocked DIO reads we have to
> rearrange wait sequence
> 1) update i_size first
> 2) if i_size about to be reduced wait for outstanding DIO requests
> 3) and only after that truncate inode blocks
Looks good. You can add:
Reviewed-by: Jan Kara <jack@suse.cz>
Honza
>
> Signed-off-by: Dmitry Monakhov <dmonakhov@openvz.org>
> ---
> fs/ext4/inode.c | 7 +++++--
> 1 files changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index ffb4a27..93e6b09 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -4283,7 +4283,6 @@ int ext4_setattr(struct dentry *dentry, struct iattr *attr)
> }
>
> if (attr->ia_valid & ATTR_SIZE) {
> - inode_dio_wait(inode);
>
> if (!(ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))) {
> struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
> @@ -4332,8 +4331,12 @@ int ext4_setattr(struct dentry *dentry, struct iattr *attr)
> }
>
> if (attr->ia_valid & ATTR_SIZE) {
> - if (attr->ia_size != i_size_read(inode))
> + if (attr->ia_size != inode->i_size) {
> truncate_setsize(inode, attr->ia_size);
> + /* Inode size will be reduced, wait for dio in flight */
> + if (orphan)
> + inode_dio_wait(inode);
> + }
> ext4_truncate(inode);
> }
>
> --
> 1.7.7.6
>
--
Jan Kara <jack@suse.cz>
SUSE Labs, CR
next prev parent reply other threads:[~2012-09-10 9:54 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-09-09 17:27 [PATCH 0/7] ext4: Bunch of DIO/AIO fixes Dmitry Monakhov
2012-09-09 17:27 ` [PATCH 1/7] ext4: ext4_inode_info diet Dmitry Monakhov
2012-09-13 10:50 ` Zheng Liu
2012-09-13 11:15 ` Dmitry Monakhov
2012-09-15 15:53 ` Theodore Ts'o
2012-09-09 17:27 ` [PATCH 2/7] ext4: completed_io locking cleanup Dmitry Monakhov
2012-09-10 9:23 ` Jan Kara
2012-09-10 10:19 ` Dmitry Monakhov
2012-09-13 10:48 ` Zheng Liu
2012-09-09 17:27 ` [PATCH 3/7] ext4: serialize dio nolocked reads with defrag workers V2 Dmitry Monakhov
2012-09-10 9:31 ` Jan Kara
2012-09-10 10:00 ` Jan Kara
2012-09-09 17:27 ` [PATCH 4/7] ext4: fsync should wait for DIO writers Dmitry Monakhov
2012-09-10 9:51 ` Jan Kara
2012-09-10 10:56 ` Dmitry Monakhov
2012-09-12 14:02 ` Jan Kara
2012-09-12 5:40 ` Zheng Liu
2012-09-13 10:46 ` Zheng Liu
2012-09-13 11:01 ` Dmitry Monakhov
2012-09-13 12:36 ` Zheng Liu
2012-09-09 17:27 ` [PATCH 5/7] ext4: serialize unlocked dio reads with truncate Dmitry Monakhov
2012-09-10 9:54 ` Jan Kara [this message]
2012-09-09 17:27 ` [PATCH 6/7] ext4: endless truncate due to nonlocked dio readers V2 Dmitry Monakhov
2012-09-13 10:41 ` Zheng Liu
2012-09-13 12:07 ` Jan Kara
2012-09-13 12:57 ` Zheng Liu
2012-09-13 14:34 ` Jan Kara
2012-09-13 23:31 ` Zheng Liu
2012-09-09 17:27 ` [PATCH 7/7] ext4: serialize truncate with owerwrite DIO workers V2 Dmitry Monakhov
2012-09-13 10:37 ` Zheng Liu
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