Hi Changwei,
On 2017/10/20 17:23, Changwei Ge wrote:
> Hi Alex,
>
> Are you able to provide a way to reproduce this issue?
> I'm very interested in it.
>
You can reproduce the BUG in the following steps:
1. touch "/mnt/ocfs2/test";
2. fallocate -l 1G "/mnt/ocfs2/test";
3. write the file "/mnt/ocfs2/test" using the io_submit();
4. at the same time, creating another process to read this file from
a random location;
> Thanks,
> Changwei.
>
> On 2017/10/20 17:08, alex chen wrote:
>> 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))
>>
>> Signed-off-by: Alex Chen <alex.c...@huawei.com>
>> Reviewed-by: Jun Piao <piao...@huawei.com>
>>
>> ---
>> fs/ocfs2/aops.c | 21 +++++++++++++++------
>> 1 file changed, 15 insertions(+), 6 deletions(-)
>>
>> diff --git a/fs/ocfs2/aops.c b/fs/ocfs2/aops.c
>> index 88a31e9..5cb939f 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;
>> + 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 +2167,8 @@ 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);
>> -
>> + ret = ocfs2_get_block_lock(inode, iblock, bh_result, create);
>> if (buffer_mapped(bh_result) &&
>> !buffer_new(bh_result) &&
>> ret == 0)
>> @@ -2424,7 +2433,7 @@ 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
>>
>>
>>
>> _______________________________________________
>> Ocfs2-devel mailing list
>> Ocfs2-devel@oss.oracle.com
>> https://oss.oracle.com/mailman/listinfo/ocfs2-devel
>>
>
>
> .
>
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