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@xxxxxxx>
Honza
>
> Signed-off-by: Dmitry Monakhov <dmonakhov@xxxxxxxxxx>
> ---
> 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@xxxxxxx>
SUSE Labs, CR
--
To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
