Re: [RFC PATCH 1/2] ovl: skip checking lower file's write permisson on truncate

[Chengguang Xu <cgxu519@mykernel.net>]

 ---- 在 星期三, 2021-07-21 00:01:11 Miklos Szeredi <miklos@szeredi.hu> 撰写 ----
 > On Tue, 20 Jul 2021 at 17:19, Miklos Szeredi <miklos@szeredi.hu> wrote:
 > 
 > > So on one instance a file on lower gets executed and on another
 > > instance sharing the lower layer the file is truncated.  The truncate
 > > is currently denied due to the negative i_writecount on the lower
 > > file.  Also behavior is inconsistent between open(path, O_TRUNC) and
 > > truncate(path) even though the two should be equivalent.
 > >
 > > Applied with the following description:
 > >
 > [...]
 > 
 > Also adding the following documentation in the "Non-standard behavior" section:
 > 
 > c) If a file residing on a lower layer is being executed, then opening that
 > file for write or truncating the file will not be denied with ETXTBSY.
 > 
 > Looked at the POSIX standard and it only documents ETXTBUSY for O_RDWR
 > and O_WRONLY and not for truncate(2) or O_TRUNC.  So strictly speaking
 > this patch doesn't even change the POSIX correctness.
 > 

Hi Miklos,

Thanks for doing this too.

Thanks,
Chengguang