Hi, We are writing a stackable file system. While testing this on NFS we came across a situation where sometimes we are getting ASCII NUL bytes in the buffer read from the lower file system (NFS in this case). This happens when NFS client 1 is writing to a file and NFS client 2 is continuously reading from the same file. A simple case like the following also shows the same problem ----------------8<------------------8<----------------------------- while (1) { if (vfs_getattr(filp->f_vfsmnt, filp->f_dentry, &stat) != 0) { printk(KERN_INFO "Error in getting attribute\n"); break; } if (no_inc == 60) { printk(KERN_INFO "File not increased for 1 min. Quitting\n"); break; } inc = stat.size - old_size; if (inc) { old_size = stat.size; no_inc = 0; count = vfs_read(filp, buf, sizeof(buf), &filp->f_pos); if (count < 0) { printk(KERN_INFO "Error in reading file\n"); goto out; } printk(KERN_INFO "File increase = [%llu], total read = [%llu]" " file_len = [%llu] File size from inode = [%llu]\n", inc, count, stat.size, i_size_read(filp->f_dentry->d_inode)); printk(KERN_INFO "----------------------------------------------------\n"); debug_dump("Read buffer", buf, total_count); } else { no_inc++; } } ----------------8<------------------8<----------------------------- We have also noticed that the expected increase (inc) and the size returned in (vfs_read()) is different. A similar program in user space also reproduces this issue. A google search for this issue tells me that others have seen this issue as well. http://stackoverflow.com/questions/6814404/java-inputstream-read-methods-ret... Is this a known and expected behaviour of NFS? PS : This is a very old kernel (2.6.18.274.) We still have to support RHEL 5 :) -- Regards, Ranjan