On Mon, Apr 23, 2018 at 3:36 PM, Vivek Goyal <vgoyal@xxxxxxxxxx> wrote:
> On Thu, Apr 12, 2018 at 05:08:04PM +0200, Miklos Szeredi wrote:
>> Implement stacked fsync().
>>
>> Signed-off-by: Miklos Szeredi <mszeredi@xxxxxxxxxx>
>> ---
>> fs/overlayfs/file.c | 20 ++++++++++++++++++++
>> 1 file changed, 20 insertions(+)
>>
>> diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c
>> index b98204c1c19c..4417527667ff 100644
>> --- a/fs/overlayfs/file.c
>> +++ b/fs/overlayfs/file.c
>> @@ -222,10 +222,30 @@ static ssize_t ovl_write_iter(struct kiocb *iocb, struct iov_iter *iter)
>> return ret;
>> }
>>
>> +static int ovl_fsync(struct file *file, loff_t start, loff_t end, int datasync)
>> +{
>> + struct fd real;
>> + const struct cred *old_cred;
>> + int ret;
>> +
>> + ret = ovl_real_file(file, &real);
>> + if (ret)
>> + return ret;
>> +
>> + old_cred = ovl_override_creds(file_inode(file)->i_sb);
>> + ret = vfs_fsync_range(real.file, start, end, datasync);
>> + revert_creds(old_cred);
>
> Can we avoid calling fsync() on real file if it is not upper. Is it worth
> optimizing.
Not sure it's worth bothering with. If caller of fsync(2) didn't
worry about cost, then why should we?
Thanks,
Miklos
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