mv: skipping file...it was replaced

We have Mosix version 1.9.0 running on Red Hat 8.0 with the Linux 2.4.20 
kernel. We now get an error from cp or mv complaining with the error 
message, "skipping file `[mfs-pathname]', as it was replaced while being 
copied". I've found and fixed the problem with a work-around, but 
there's a Mosix question you may want to look at.

The problem happens in fileutils-4.1.9-11, the current version. In 
sys2.h is a SAME_INODE() macro defined to compare both the st_ino and 
st_dev. If two statbufs passed to the macro compare the same for both 
components, the macro returns a TRUE. While that logic makes sense to me 
for comparing a source file with a destination file for cp or mv, there 
is one place in copy.c in the beginning of the function copy_reg() where 
the source file is compared with itself to see if a change has happened 
since the operation began. In copy_internal(), either stat() or lstat() 
is called on the source file to give the 1st statbuf. Later, 
copy_internal() calls copy_reg(), which immediately opens the source 
file then calls fstat() to give the 2nd statbuf.

Unfortunately, Mosix changes the st_dev when a file is opened on the 
/mfs filesystem. Therefore, what stat() & lstat() report is different 
from what fstat() reports, so cp & mv both think the source file has 
changed and abort the operation. I was able to correct the problem by 
using a different version of SAME_INODE() that compares only the st_ino 
at that stage, not st_dev. I can't think of any reason why a single file 
would change its device without changing its inode, so I think 
SAME_INODE() has been logically overused in copy.c.

I've added the following macro in sys2.h:

448a449,451
 > #define SAME_INODE_ONLY(Stat_buf_1, Stat_buf_2) \
 >   ((Stat_buf_1).st_ino == (Stat_buf_2).st_ino)
 >

Then, in copy.c, in the function copy_reg(), I've changed the first 
reference to SAME_INODE into SAME_INODE_ONLY:

239c239
<   if (! SAME_INODE (*src_sb, src_open_sb))
---
 >   if (! SAME_INODE_ONLY (*src_sb, src_open_sb))

With these in place, cp & mv work correctly on the Mosix /mfs 
filesystem. I have also reported this to the Mosix and openMosix teams, 
suggesting that they may not want to change the st_dev that fstat() 
reports from what stat() and lstat() reports.

--Larry

-- 
Larry Reznick			 Sr Software Developer
Interact Devices, Inc		     916-673-1860 x225
160 Blue Ravine Rd Suite B	      Fax 916-669-0035
Folsom, CA 95630-4718			   idicorp.net