[Ocfs2-devel] [PATCH 1/1] Ocfs2: Teach 'coherency=full' O_DIRECT writes to correctly up_read i_alloc_sem.
Tristan Ye
tristan.ye at oracle.com
Mon Dec 6 17:47:05 PST 2010
Joel Becker wrote:
> On Mon, Nov 29, 2010 at 05:21:46PM +0800, Tristan Ye wrote:
>> diff --git a/fs/ocfs2/aops.c b/fs/ocfs2/aops.c
>> index f1e962c..857e013 100644
>> --- a/fs/ocfs2/aops.c
>> +++ b/fs/ocfs2/aops.c
>> @@ -568,7 +568,7 @@ static void ocfs2_dio_end_io(struct kiocb *iocb,
>> bool is_async)
>> {
>> struct inode *inode = iocb->ki_filp->f_path.dentry->d_inode;
>> - int level;
>> + int level, sem_locked;
>>
>> /* this io's submitter should not have unlocked this before we could */
>> BUG_ON(!ocfs2_iocb_is_rw_locked(iocb));
>> @@ -576,7 +576,9 @@ static void ocfs2_dio_end_io(struct kiocb *iocb,
>> ocfs2_iocb_clear_rw_locked(iocb);
>>
>> level = ocfs2_iocb_rw_locked_level(iocb);
>> - if (!level)
>> + sem_locked = ocfs2_iocb_is_sem_locked(iocb);
>> + ocfs2_iocb_clear_sem_locked(iocb);
>> + if (sem_locked)
>> up_read(&inode->i_alloc_sem);
>> ocfs2_rw_unlock(inode, level);
>
> I agree with Tao, we don't need sem_locked. Just do:
>
> if (ocfs2_iocb_is_sem_locked(iocb)) {
> up_read(&inode->i_alloc_sem);
> ocfs2_iocb_clear_sem_locked(iocb);
> }
>
> I think it reads better.
>
>> diff --git a/fs/ocfs2/aops.h b/fs/ocfs2/aops.h
>> index 76bfdfd..c7a3e5f 100644
>> --- a/fs/ocfs2/aops.h
>> +++ b/fs/ocfs2/aops.h
>> @@ -72,4 +72,10 @@ static inline void ocfs2_iocb_set_rw_locked(struct kiocb *iocb, int level)
>> clear_bit(0, (unsigned long *)&iocb->private)
>> #define ocfs2_iocb_rw_locked_level(iocb) \
>> test_bit(1, (unsigned long *)&iocb->private)
>> +#define ocfs2_iocb_set_sem_locked(iocb) \
>> + set_bit(2, (unsigned long *)&iocb->private)
>> +#define ocfs2_iocb_clear_sem_locked(iocb) \
>> + clear_bit(2, (unsigned long *)&iocb->private)
>> +#define ocfs2_iocb_is_sem_locked(iocb) \
>> + test_bit(2, (unsigned long *)&iocb->private)
>
> Give these bits an enum. Anonymous numbers aren't good. And
> make the comment better.
Sounds more reasonable;)
>
>> #endif /* OCFS2_FILE_H */
>> diff --git a/fs/ocfs2/file.c b/fs/ocfs2/file.c
>> index 77b4c04..0e9d729 100644
>> --- a/fs/ocfs2/file.c
>> +++ b/fs/ocfs2/file.c
>> @@ -2246,7 +2246,10 @@ relock:
>> if (direct_io) {
>> down_read(&inode->i_alloc_sem);
>> have_alloc_sem = 1;
>> - }
>> + /* communicate with ocfs2_dio_end_io */
>> + ocfs2_iocb_set_sem_locked(iocb);
>> + } else
>> + ocfs2_iocb_clear_sem_locked(iocb);
>
> I understand you're trying to avoid bad bits here, but you
> should explicitly clear it at the top of the function. You know for a
> fact that, at the top (right before relock:), there is no sem held.
> Then set it as you do, and only re-clear it when you up_write().
Alright.
>
> Joel
>
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