| Message ID | 1347211634-11509-6-git-send-email-dmonakhov@openvz.org |
|---|---|
| State | Superseded, archived |
| Headers | show |
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 >
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); }
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 Signed-off-by: Dmitry Monakhov <dmonakhov@openvz.org> --- fs/ext4/inode.c | 7 +++++-- 1 files changed, 5 insertions(+), 2 deletions(-)