[Ocfs2-devel] [PATCH v2] ocfs2: the ip_alloc_sem should be taken in ocfs2_get_block()

[alex chen]

Hi Everybody,

Thanks for your reviews.

I agree with Gang to make function name ocfs2_get_block_lock() more
readable. But the ocfs2_get_block_lock() may be called by the
ocfs2_dio_get_block() in re-write sitiation, so I don't think the
ocfs2_dio_rd_get_block() is a better name. I agree with Joseph and
rename it to ocfs2_lock_get_block().

BTW, I think the ocfs2_dio_wr_get_block() is more suitable for the
ocfs2_dio_get_block().

Please give me any feedback if you have any suggestions.

Thanks
Alex

On 2017/10/23 15:16, Gang He wrote:
> Hello Alex,
> 
> Base on your bug description, I think that the fix should be OK.
> But I suggest you to use more clear function name in this patch.
> 1) For new-added function ocfs2_get_block_lock(), I think that it is better if the function name is ocfs2_dio_rd_get_block().
> 2) Then, rename the original function ocfs2_dio_get_block() to ocfs2_dio_wr_get_block().
> Why? 
> Since this function looks to only be used by direct IO (read) mode, 
> we should make the function name more clear, do NOT make other developer to misunderstand/misuse it in the future.
> 
> Thanks
> Gang 
> 
> 
>>>>
>> The ip_alloc_sem should be taken in ocfs2_get_block() when reading file
>> in DIRECT mode to prevent concurrent access to extent tree with
>> ocfs2_dio_end_io_write(), which may cause BUGON in
>> ocfs2_get_clusters_nocache()->BUG_ON(v_cluster < le32_to_cpu(rec->e_cpos))
>>
>> Fixes: c15471f79506 ("ocfs2: fix sparse file & data ordering issue in direct 
>> io")
>>
>> Signed-off-by: Alex Chen <alex.chen at huawei.com>
>> Reviewed-by: Jun Piao <piaojun at huawei.com>
>> Acked-by: Changwei Ge <ge.changwei at h3c.com>
>>
>> ---
>>  fs/ocfs2/aops.c | 22 ++++++++++++++++------
>>  1 file changed, 16 insertions(+), 6 deletions(-)
>>
>> diff --git a/fs/ocfs2/aops.c b/fs/ocfs2/aops.c
>> index 88a31e9..29607d9 100644
>> --- a/fs/ocfs2/aops.c
>> +++ b/fs/ocfs2/aops.c
>> @@ -134,6 +134,19 @@ static int ocfs2_symlink_get_block(struct inode *inode, 
>> sector_t iblock,
>>  	return err;
>>  }
>>
>> +static int ocfs2_get_block_lock(struct inode *inode, sector_t iblock,
>> +		    struct buffer_head *bh_result, int create)
>> +{
>> +	int ret = 0;
>> +	struct ocfs2_inode_info *oi = OCFS2_I(inode);
>> +
>> +	down_read(&oi->ip_alloc_sem);
>> +	ret = ocfs2_get_block(inode, iblock, bh_result, create);
>> +	up_read(&oi->ip_alloc_sem);
>> +
>> +	return ret;
>> +}
>> +
>>  int ocfs2_get_block(struct inode *inode, sector_t iblock,
>>  		    struct buffer_head *bh_result, int create)
>>  {
>> @@ -2154,12 +2167,9 @@ static int ocfs2_dio_get_block(struct inode *inode, 
>> sector_t iblock,
>>  	 * while file size will be changed.
>>  	 */
>>  	if (pos + total_len <= i_size_read(inode)) {
>> -		down_read(&oi->ip_alloc_sem);
>> -		/* This is the fast path for re-write. */
>> -		ret = ocfs2_get_block(inode, iblock, bh_result, create);
>> -
>> -		up_read(&oi->ip_alloc_sem);
>>
>> +		/* This is the fast path for re-write. */
>> +		ret = ocfs2_get_block_lock(inode, iblock, bh_result, create);
>>  		if (buffer_mapped(bh_result) &&
>>  		    !buffer_new(bh_result) &&
>>  		    ret == 0)
>> @@ -2424,7 +2434,7 @@ static ssize_t ocfs2_direct_IO(struct kiocb *iocb, 
>> struct iov_iter *iter)
>>  		return 0;
>>
>>  	if (iov_iter_rw(iter) == READ)
>> -		get_block = ocfs2_get_block;
>> +		get_block = ocfs2_get_block_lock;
>>  	else
>>  		get_block = ocfs2_dio_get_block;
>>
>> -- 
>> 1.9.5.msysgit.1
>>
>>
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> 
> 
> .
>