| Message ID | 1348847051-6746-8-git-send-email-dmonakhov@openvz.org |
|---|---|
| State | Accepted, archived |
| Headers | show |
On Fri, Sep 28, 2012 at 07:44:07PM +0400, Dmitry Monakhov wrote: > if (attr->ia_valid & ATTR_SIZE) { > - if (attr->ia_size != i_size_read(inode)) > + if (attr->ia_size != inode->i_size) { Why this change? Why are you not using i_size_read() here? - Ted -- 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
On Sat, 29 Sep 2012 00:49:04 -0400, "Theodore Ts'o" <tytso@mit.edu> wrote: > On Fri, Sep 28, 2012 at 07:44:07PM +0400, Dmitry Monakhov wrote: > > if (attr->ia_valid & ATTR_SIZE) { > > - if (attr->ia_size != i_size_read(inode)) > > + if (attr->ia_size != inode->i_size) { > > Why this change? Why are you not using i_size_read() here? Since we hold i_mutex no one is able to change i_size, and it is safe to access it directly. > > - Ted -- 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
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c index da52855..583cb3f 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -4255,7 +4255,6 @@ 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); @@ -4304,8 +4303,12 @@ 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 Reviewed-by: Jan Kara <jack@suse.cz> Signed-off-by: Dmitry Monakhov <dmonakhov@openvz.org> --- fs/ext4/inode.c | 7 +++++-- 1 files changed, 5 insertions(+), 2 deletions(-)