Hello,
Currently it is possible for some errors to be detected at write-back
time but not reported to the program as shown by the following script
using the included make_file.c.
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#!/bin/sh
# We binary search the size of a file in 40M filesystem that can cause
# the missed error.
MIN=5000000
MAX=50000000
rm fs.40M
dd if=/dev/zero of=fs.40M bs=40M count=0 seek=1 status=noxfer
mkfs.ext2 -F fs.40M
#mkfs.ext3 -F fs.40M
#mkfs.jfs -q fs.40M
#mkfs.reiserfs -fq fs.40M
#mkfs.xfs fs.40M
attempt()
{
SIZE=$1
RES=0
./make_file valid_file $SIZE
mount fs.40M /mnt -o loop
if ! ./make_file /mnt/not_enough_space $SIZE; then
# We could not create the file as the requested size
# was clearly too big
RES=1
fi
umount /mnt
if [ $RES -eq 0 ]; then
mount fs.40M /mnt -o loop
if cmp valid_file /mnt/not_enough_space; then
# The file was too small, it fitted in the filesystem
RES=-1
fi
umount /mnt
fi
if [ $RES -eq 0 ]; then
echo "Undetected ENOSPC with SIZE=$SIZE"
exit
fi
return $RES
}
while [ $((MAX - MIN)) -gt 1 ]; do
SIZE=$(((MIN + MAX) / 2))
attempt $SIZE
RES=$?
if [ $RES -eq 1 ]; then
MAX=$SIZE
else
MIN=$SIZE
fi
done
echo "Could not reproduce the problem"
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/* make_file.c */
#include <unistd.h>
#include <sys/fcntl.h>
#include <sys/mman.h>
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
int main(int argc, char **argv)
{
int size, fd;
char *mapping;
if (argc != 3) {
fprintf(stderr, "Usage: %s FILE SIZE\n", argv[0]);
return 1;
}
size = atoi(argv[2]);
fd = open(argv[1], O_RDWR | O_CREAT, 0600);
if (fd < 0) {
perror(argv[1]);
return 1;
}
if (ftruncate(fd, size) < 0) {
perror("ftruncate");
return 1;
}
mapping = mmap(NULL, size,...
