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:
> 
>> > +                       rvap->va_size = MAX(rvap->va_size, vp->v_size);
>> > + 
>> couldn't it be a problem if the size of the file is shrinked by the server?
> 
> I am back to this simple fix, after the failure of attempts to avoid
> uvm_vnp_setsize() calls from puffs_vnop_getattr() while a
> PUFFS_VN_SETATTR is in progress. 
> 
> Keeping track of the end of a PUFFS_VN_SETATTR operation turns to be
> troublesome. The operation needs to be asynchronous when done by a
> kernel thread responsible for freeing memory, otherwise we get a
> deadlock. Using puffs_msg_setcall() to get notified of completion does
> not help, as soon as I use it, the machine hangs on low memory
> situation.

ioflush (syncer) is not a kernel thread responsible for freeing memory.
pagedaemon is.

i don't think syncer alone can deadlock with puffs.

YAMAMOTO Takashi

> 
> Keeping MAX(rvap->va_size, vp->v_size) in puffs_vnop_getattr() is simple
> but it has a drawback with distributed filesystems: a client will not
> notify that an open file was shrunk by another client. I think this is
> better than deadlocks and data corruption. 
> 
> If nobody has a better idea, I will got with this simple fix.
> 
> -- 
> Emmanuel Dreyfus
> http://hcpnet.free.fr/pubz
> manu%netbsd.org@localhost