Re: [PATCH 17/19] xfsprogs: disable truncating of files

Dave Chinner
2016-04-08T00:23:52Z

On Thu, Mar 24, 2016 at 12:15:34PM +0100, jtulak@redhat.com wrote:
> From: Jan Tulak <jtulak@redhat.com>
>
> Unify mkfs.xfs behaviour a bit and never truncate files. If the user
> is trying to mkfs an existing file, we don't want to destroy anything
> he did with the file before (sparse file, allocations...)

Why not? We do that with discard-by-default to block devices,
O_TRUNC is exactly the same situation with a file - we completely
re-initialise the file from a known state if mkfs has been asked to
create the file.

> @@ -1059,9 +1063,9 @@ check_device_type(
> }
>
> /*
> - * We only want to completely truncate and recreate an existing file if
> - * we were specifically told it was a file. Set the create flag only in
> - * this case to trigger that behaviour.
> + * We only want to create a file only if we were specifically told
> + * we want a file. Set the create flag only in this case to trigger
> + * that behaviour.
> */
> if (S_ISREG(statbuf.st_mode)) {
> if (!*isfile)

i.e. this situation.

Cheers,

Dave.
--
Dave Chinner
david@fromorbit.com