[OpenAFS-devel] Client bug in afs_segments.c

[Christof Hanke]

Hello List,

together with a user and Hartmut, I guess I found a bug in the function
afs_TruncateAllSegments() in afs_segments.c.
Basically, the pointers (struct dcache *)->validPos and (struct dcache *)->=
f.chunkBytes are not kept in sync.

Here the patch :

diff -ur /usr/src/openafs-1.3.71/src/afs/afs_segments.c afs_segments.c
--- /usr/src/openafs-1.3.71/src/afs/afs_segments.c      2004-08-25 09:09:32=
=2E000000000 +0200
+++ afs_segments.c      2004-09-10 12:18:08.000000000 +0200
@@ -1041,6 +1041,12 @@
            afs_CFileTruncate(tfile, newSize);
            afs_CFileClose(tfile);
            afs_AdjustSize(tdc, newSize);
+           if (alen < tdc->validPos) {
+                if (alen < AFS_CHUNKTOBASE(tdc->f.chunk))
+                    tdc->validPos =3D 0;
+                else
+                    tdc->validPos =3D alen;
+            }
            ConvertWToSLock(&tdc->lock);
        }
        ReleaseSharedLock(&tdc->lock);
My guess is that the same bug is in the 1.2.x-series as well.

The consequences of this bug can be tested with this program
(you have to set the macro !) :

On rh9 or suse 9.0 on a single CPU machine it gives an i/o-error,
a SMP machine freezes. (At least for me)
=20

#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>

#define FILE_IN_AFS "ABSOLUTE_PATH_TO_AFS_FILE"

int main() {
  FILE *fp;
  int i,fd;
  char fname[]=3D FILE_IN_AFS;
  char pr_string[]=3D" Hallo\n";
  off_t size=3D0;
  fp =3Dfopen(fname,"w+");
  for (i=3D0;i < 1000;i++)
     fprintf(fp," Hallo\n");
  fclose(fp);
  fp =3Dfopen(fname,"a");
  fd=3Dfileno(fp);
  rewind(fp);
  for (i=3D0;i < 50;i++)
     size+=3Dsizeof(pr_string);
     fprintf(fp,pr_string);
  fflush(fp);
  ftruncate(fd,size);
  fclose(fp);
 return 0;
}


I hope that helps.

Christof Hanke

-----------------------------------------------------------------
Christof Hanke                 =09=09e-mail hanke@rzg.mpg.de
RZG (Rechenzentrum Garching)=09=09phone +49-89-3299-1788
Computing Center of the Max-Planck-Gesellschaft (MPG) and the
Institut f=FCr Plasmaphysik (IPP)