Question about file size 0 after filesystem recovery

[Joel Sherrill]

On Tue, Jan 5, 2021 at 12:48 AM jaeho jo <hot486two at gmail.com> wrote:

> Hello!
>
> I am testing filesystem recovery and I have a question.
>
> If the reset is not a power-on reset, my application attempts to restore
> the filesystem.
>
> If the file was closed prior to reset, the file was restored.
>
> If a reset occurs while a file is open, the file was not recovered after
> the reset. The file was created, but its size is 0. Is this the
> intended behavior of RTEMS?
>
> I tested the OS version using RTEMS4.11.1 and 5.1, and the file system
> using RFS and dosFS. The results were all the same. A file of size 0 has
> been created.
>

If the file and underlying disk buffers are not flushed before reset, then
nothing has been committed to the non-volatile storage.

I would say this is expected and intended behavior if you do not have an
orderly write of a file on shutdown/reset on any operating system.

My quick look at the source code for both filesystems you mention indicate
the sync calls like fsync() and fdatasync() are supported. Here is the
POSIX page for fsync(). Notice the discussion at the bottom about automated
testing and reset.

https://pubs.opengroup.org/onlinepubs/009695399/functions/fsync.html

I assume this also flushes the block device cache but I didn't look beyond
the file system implementations.

--joel


> thanks!
> jhjo
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