[PATCH 13/25] ubifs: introduce a field named as budgeted to ubifs_inode
Dongsheng Yang
yangds.fnst at cn.fujitsu.com
Tue Jul 21 17:56:04 PDT 2015
On 07/22/2015 04:47 AM, Richard Weinberger wrote:
> Am 21.07.2015 um 10:37 schrieb Dongsheng Yang:
>> There is a long-term pain in ubifs, we have to introduce a
>> ui_mutex in ubifs_inode to solve two problems below:
>>
>> 1: make some process atomic, such as ubifs_rename.
>> 2: make sure we budget space for inode before dirting it.
>>
>> About 1, it's true and we have to do it.
>>
>> About 2, we can do it better.
>> There is a ubifs_assert(mutex_is_locked(&ui->mutex)) in
>> ubifs_dirty_inode(). But there is probably some processes
>> are very long, and we can not make all of it into a pair of
>> lock/unlock ui->mutex.
>>
>> E.g: dquot_disable().
>> It would mark the quota files as dirty and write the
>> inode back. We can do a budget before this function, but we
>> can not make the whole dquot_disable() into mutex_lock/mutex_unlock.
>> Because we need to lock the ui_mutex in dquot_disable().
>>
>> So, this commit introduce a ui->budgeted to allow us to make
>> budgeting and dirting in two different lock windows.
>>
>> Result:
>> ubifs_budget_space()
>> mutex_lock();
>> ui->budgeted = 1;
>> mutex_unlock();
>> ...
>> dquot_disable();
>
> I'm confused by this changelog.
Sorry, it is indeed confusing. Let me try to explain it more.
Currently, we have a ubifs_assert(mutex_is_locked(&ui->ui_mutex));
in ubifs_dirty_inode(). The reason of it is to make sure we have
done the budget before dirting it.
So we have to use it like that:
struct ubifs_budget_req req = { .dirtied_ino = 1};
ubifs_budget_space(req);
mutex_lock(&ui->ui_mutex);
ubifs_dirty_inode();
mutex_unlock(&ui->ui_mutex);
We are checking the ui_mutex in ubifs_dirty_inode() to make sure
we are taking a full control of this process and we are sure there
is enough space to write this inode.
But the problem is: we can not put all process which are going to
dirty inode into the lock window, such as dquot_disable(), it will
acquire the ui_mutex in itself. (Although we can blame vfs to dirty
inode without asking ubifs is that correct)
So, I introduce a ui->budgeted here to replace ubifs_assert() in
ubifs_dirty_inode(); In ubifs_dirty_inode(), we can only check
the ui->budgeted to know whether we have done the budget for this
inode. Take the advantage of it, we can get what we want and solve
the problem I mentioned above.
I hope it more clear.
Thanx
Yang
>
> Why do you need ui->budgeted? You set it but never read it
> except in an ubifs_assert().
>
>> Signed-off-by: Dongsheng Yang <yangds.fnst at cn.fujitsu.com>
>> ---
>> fs/ubifs/file.c | 7 +++++++
>> fs/ubifs/ioctl.c | 1 +
>> fs/ubifs/super.c | 14 +++++++++++++-
>> fs/ubifs/ubifs.h | 1 +
>> 4 files changed, 22 insertions(+), 1 deletion(-)
>>
>> diff --git a/fs/ubifs/file.c b/fs/ubifs/file.c
>> index dc8bf0b..113c3a6 100644
>> --- a/fs/ubifs/file.c
>> +++ b/fs/ubifs/file.c
>> @@ -307,6 +307,7 @@ static int write_begin_slow(struct address_space *mapping,
>> * budget we allocated.
>> */
>> ubifs_release_dirty_inode_budget(c, ui);
>> + ui->budgeted = 1;
>> }
>>
>> *pagep = page;
>> @@ -357,6 +358,7 @@ static int allocate_budget(struct ubifs_info *c, struct page *page,
>> * we need to budget the inode change.
>> */
>> req.dirtied_ino = 1;
>> + ui->budgeted = 1;
>> } else {
>> if (PageChecked(page))
>> /*
>> @@ -384,6 +386,7 @@ static int allocate_budget(struct ubifs_info *c, struct page *page,
>> * needs a budget.
>> */
>> req.dirtied_ino = 1;
>> + ui->budgeted = 1;
>> }
>> }
>>
>> @@ -1237,6 +1240,7 @@ static int do_setattr(struct ubifs_info *c, struct inode *inode,
>> do_attr_changes(inode, attr);
>>
>> release = ui->dirty;
>> + ui->budgeted = 1;
>> if (attr->ia_valid & ATTR_SIZE)
>> /*
>> * Inode length changed, so we have to make sure
>> @@ -1397,6 +1401,7 @@ static int ubifs_update_time(struct inode *inode, struct timespec *time,
>> iflags |= I_DIRTY_SYNC;
>>
>> release = ui->dirty;
>> + ui->budgeted = 1;
>> __mark_inode_dirty(inode, iflags);
>> mutex_unlock(&ui->ui_mutex);
>> if (release)
>> @@ -1430,6 +1435,7 @@ static int update_mctime(struct inode *inode)
>> mutex_lock(&ui->ui_mutex);
>> inode->i_mtime = inode->i_ctime = ubifs_current_time(inode);
>> release = ui->dirty;
>> + ui->budgeted = 1;
>> mark_inode_dirty_sync(inode);
>> mutex_unlock(&ui->ui_mutex);
>> if (release)
>> @@ -1556,6 +1562,7 @@ static int ubifs_vm_page_mkwrite(struct vm_area_struct *vma,
>> mutex_lock(&ui->ui_mutex);
>> inode->i_mtime = inode->i_ctime = ubifs_current_time(inode);
>> release = ui->dirty;
>> + ui->budgeted = 1;
>> mark_inode_dirty_sync(inode);
>> mutex_unlock(&ui->ui_mutex);
>> if (release)
>> diff --git a/fs/ubifs/ioctl.c b/fs/ubifs/ioctl.c
>> index 3c7b29d..f015b81 100644
>> --- a/fs/ubifs/ioctl.c
>> +++ b/fs/ubifs/ioctl.c
>> @@ -128,6 +128,7 @@ static int setflags(struct inode *inode, int flags)
>> ubifs_set_inode_flags(inode);
>> inode->i_ctime = ubifs_current_time(inode);
>> release = ui->dirty;
>> + ui->budgeted = 1;
>> mark_inode_dirty_sync(inode);
>> mutex_unlock(&ui->ui_mutex);
>>
>> diff --git a/fs/ubifs/super.c b/fs/ubifs/super.c
>> index 2491fff..5fa21d6 100644
>> --- a/fs/ubifs/super.c
>> +++ b/fs/ubifs/super.c
>> @@ -331,6 +331,7 @@ static int ubifs_write_inode(struct inode *inode, struct writeback_control *wbc)
>> }
>>
>> ui->dirty = 0;
>> + ui->budgeted = 0;
>> mutex_unlock(&ui->ui_mutex);
>> ubifs_release_dirty_inode_budget(c, ui);
>> return err;
>> @@ -386,12 +387,23 @@ done:
>> static void ubifs_dirty_inode(struct inode *inode, int flags)
>> {
>> struct ubifs_inode *ui = ubifs_inode(inode);
>> + int need_unlock = 0;
>>
>> - ubifs_assert(mutex_is_locked(&ui->ui_mutex));
>> + if (unlikely(!mutex_is_locked(&ui->ui_mutex))) {
>> + /* We need to lock ui_mutex to access ui->budgeted */
>> + mutex_lock(&ui->ui_mutex);
>> + need_unlock = 1;
>> + }
>> +
>> + /* Check the budget for this inode */
>> + ubifs_assert(ui->budgeted);
>> if (!ui->dirty) {
>> ui->dirty = 1;
>> dbg_gen("inode %lu", inode->i_ino);
>> }
>> +
>> + if (need_unlock)
>> + mutex_unlock(&ui->ui_mutex);
>> }
>>
>> static int ubifs_statfs(struct dentry *dentry, struct kstatfs *buf)
>> diff --git a/fs/ubifs/ubifs.h b/fs/ubifs/ubifs.h
>> index 9754bb6..28392a6 100644
>> --- a/fs/ubifs/ubifs.h
>> +++ b/fs/ubifs/ubifs.h
>> @@ -410,6 +410,7 @@ struct ubifs_inode {
>> unsigned int xattr_cnt;
>> unsigned int xattr_names;
>> unsigned int dirty:1;
>> + unsigned int budgeted:1;
>
> Please document that new flag too.
>
> Thanks,
> //richard
> .
>
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