Re: [PATCH 15/19] mkfs: don't treat files as though they are block devices

[Jan Tulak <jtulak@xxxxxxxxxx>]

On Thu, Apr 21, 2016 at 10:13 PM, Eric Sandeen <sandeen@xxxxxxxxxxx> wrote:

On 4/21/16 8:43 AM, Jan Tulak wrote:
> On Thu, Apr 21, 2016 at 11:39 AM, Jan Tulak <jtulak@xxxxxxxxxx <mailto:jtulak@xxxxxxxxxx>>wrote:
>
>Â Â ÂFrom: Dave Chinner <dchinner@xxxxxxxxxx <mailto:dchinner@xxxxxxxxxx>>
>
>Â Â ÂTHIS PATCH HAS KNOWN ISSUES - it fails xfs/206 and xfs/216 tests, as it
>Â Â Âshrinks a file instead just not using it entirely, when -d size is used.
>
>
> âSo the shrinking is happening here:
> 3127Â Â Â Â /*
> 3128Â Â Â Â Â* If the data area is a file, then grow it out to its final size
> 3129Â Â Â Â Â* so that the reads for the end of the device in the mount code
> 3130Â Â Â Â Â* will succeed.
> 3131Â Â Â Â Â*/
> 3132Â Â Â Â if (xi.disfile && ftruncate64(xi.dfd, dblocks * blocksize) < 0) {â
>
>
> Before the patch, xi.disfile was 0 and so it didn't shrink the file
> to the size of the new FS. Now, what is the correct solve to this?
> Tests are written for the old behaviour, but this shrinking seems to
> be an intentional thing. It seems that the FS works ok even when this
> truncating is not applied, so I think that I should remove this chunk
> (or change it to xi.dcreate=1 only), and keep the old behaviour.
>
> What do you think about it, guys?

Can't remove it; that would break the other side of things, if you try
to mkfs.xfs -d size=2g on an existing 1g file... mount tries to do
IO to the last block, and if it's not truncated out, that will fail
(as the comment says).

I suppose the simple way to fix it is to only truncate up, never down.

i.e. truncate to max(dblocks * blocksize, st_size) or
if (xi.disfile && st_size <Â dblocks * blocksize) { truncate ... }

All right, it seems that I should have read the man page, and not just Âlook on the first sentence or two... <emoticon of me hitting a wall with my head repeatedly>.Â

Now it works, thanks.

Jan

Â

--

Jan Tulak

jtulak@xxxxxxxxxxÂ/ jan@xxxxxxxx