Re: [PATCH] Re: zero-filed page on VOP_PUTPAGES

[yamt%mwd.biglobe.ne.jp@localhost (YAMAMOTO Takashi)]

hi,

> YAMAMOTO Takashi <yamt%mwd.biglobe.ne.jp@localhost> wrote:
> 
>> > We would have a PNODE_IN_RESIZE flag for struct pnode's pn_stat, set and
>> > cleared in dosetattr(), and use vp->v_size on uvm_vnp_setsize() calls
>> > when set? Or just avoid uvm_vnp_setsize() calls?
>> 
>> just avoid the calls.
> 
> There is a problem if two threads enter dosetattr() at the same time:
> the flag would be cleared on first thread completing the operation, and
> we get the same race again.

is there any particular order between threads in that case?
otherwise, a pending setattr counter should be enough.  getattr ignores
a part of file attributes from the file server unless the counter is 0.

YAMAMOTO Takashi

> 
> Therefore I think a mutex must guard setattr/uvm_vnp_setsize in
> dosettatr(). Does it makes sense to reuse an existing mutex (which
> one?), or should I introduce a new one, for instance pn_inrewrite in
> struct pnode?
> 
> -- 
> Emmanuel Dreyfus
> http://hcpnet.free.fr/pubz
> manu%netbsd.org@localhost