[Bug 230851] fsck sets last modified file size to zero on crash on UFS filesystem

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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=230851

Kirk McKusick <mckusick at FreeBSD.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|New                         |Closed
         Resolution|---                         |Not A Bug

--- Comment #3 from Kirk McKusick <mckusick at FreeBSD.org> ---
(In reply to Ali Abdallah from comment #2)
I have looked at nano and it does not follow the proper protocol for writing
out the file (which is detailed in my comment #1). It simply does:

fd = open(file, O_WRONLY|O_CREAT|O_TRUNC, 0666);
write new contents
close(fd);

The O_TRUNC flag truncates the file to zero length. If the system crashes
before the new contents are written, you get a zero length file. By default the
contents will not be written for up to 30 seconds. So if you panic within 30
seconds of the file being written, you will get a zero length file. The proper
way to fix this is detailed in my comment #1. The gap could be closed
significantly by adding an fsync(fd) before calling close as that would cause
the file to be written to disk within a few milliseconds of its finishing being
written thus closing the gap considerably (but it would still be possible to
get a zero length file). So, it really should be fixed properly.

I am closing this bug because it is a bug in nano and not in FreeBSD.

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