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

[manu%netbsd.org@localhost (Emmanuel Dreyfus)]

Emmanuel Dreyfus <manu%netbsd.org@localhost> wrote:

> > > +                       rvap->va_size = MAX(rvap->va_size, vp->v_size);
> I am back to this simple fix

Here is an alternative approach that works around the data corruption
bug, it seems much cleaner to me. 

It does not address the crash on low memory situation, but as I said
this one is a second different bug.

Index: sys/fs/puffs/puffs_vnops.c
===================================================================
RCS file: /cvsroot/src/sys/fs/puffs/puffs_vnops.c,v
retrieving revision 1.129.4.9
diff -u -p -d -r1.129.4.9 puffs_vnops.c
--- sys/fs/puffs/puffs_vnops.c  17 Jul 2011 15:36:03 -0000
1.129.4.9
+++ sys/fs/puffs/puffs_vnops.c  25 Aug 2011 22:56:27 -0000
@@ -855,6 +855,18 @@ puffs_vnop_getattr(void *v)
        struct vattr *vap, *rvap;
        struct puffs_node *pn = VPTOPP(vp);
        int error = 0;
+       int locked;
+
+       /*
+        * A lock is required so that we do not race with 
+        * setattr, write and fsync when changing vp->v_size.
+        * This is critical, since setting a stall smaler value
+        * triggers a file truncate in uvm_vnp_setsize(), which
+        * most of the time means data corruption (a chunk of
+        * data is replaced by zeroes).
+        */
+       if ((locked = VOP_ISLOCKED(vp)) != LK_EXCLUSIVE)
+               vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
 
        REFPN(pn);
        vap = ap->a_vap;
@@ -906,6 +918,10 @@ puffs_vnop_getattr(void *v)
  out:
        puffs_releasenode(pn);
        PUFFS_MSG_RELEASE(getattr);
+       
+       if (locked != LK_EXCLUSIVE)
+               VOP_UNLOCK(vp, 0);
+
        return error;
 }
 

-- 
Emmanuel Dreyfus
http://hcpnet.free.fr/pubz
manu%netbsd.org@localhost