Re: CVS commit: src/sys/kern

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

hi,

> Module Name:  src
> Committed By: rmind
> Date:         Wed Oct 27 02:58:05 UTC 2010
> 
> Modified Files:
>       src/sys/kern: sys_descrip.c
> 
> Log Message:
> do_posix_fadvise: check for a negative length; truncate the offset and
> round the end-offset, not vice-versa.

the latter part seems incorrect and makes putpages panic.
note that round_page(INT64_MAX) is negative.

how about the attached patch?

YAMAMOTO Takashi

> 
> Thanks to jakllsch@ for debug info.
> 
> 
> To generate a diff of this commit:
> cvs rdiff -u -r1.17 -r1.18 src/sys/kern/sys_descrip.c
> 
> Please note that diffs are not public domain; they are subject to the
> copyright notices on the relevant files.

Index: sys_descrip.c
===================================================================
RCS file: /cvsroot/src/sys/kern/sys_descrip.c,v
retrieving revision 1.18
diff -u -p -r1.18 sys_descrip.c
--- sys_descrip.c       27 Oct 2010 02:58:04 -0000      1.18
+++ sys_descrip.c       11 Nov 2010 14:06:40 -0000
@@ -680,9 +680,21 @@ do_posix_fadvise(int fd, off_t offset, o
 
        case POSIX_FADV_DONTNEED:
                vp = fp->f_data;
-               mutex_enter(&vp->v_interlock);
-               error = VOP_PUTPAGES(vp, trunc_page(offset),
-                   round_page(endoffset), PGO_DEACTIVATE | PGO_CLEANIT);
+               /*
+                * align the region to page boundaries as VOP_PUTPAGES expects
+                * by shrinking it.  we shrink instead of expand because we
+                * don't want to deactivate cache outside of the requested
+                * region.  it means that, if the specified region is smaller
+                * than PAGE_SIZE, we do nothing.
+                */
+               if (endoffset - offset >= PAGE_SIZE) {
+                       mutex_enter(&vp->v_interlock);
+                       error = VOP_PUTPAGES(vp, round_page(offset),
+                           trunc_page(endoffset),
+                           PGO_DEACTIVATE | PGO_CLEANIT);
+               } else {
+                       error = 0;
+               }
                break;
 
        case POSIX_FADV_NOREUSE: