linux-kernel - Re: [PATCH] tmpfs: truncate at i

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Message-ID: <alpine.LSU.2.11.1506161256490.1050@eggly.anvils>
Date:	Tue, 16 Jun 2015 13:02:15 -0700 (PDT)
From:	Hugh Dickins <hughd@...gle.com>
To:	Josef Bacik <jbacik@...com>
cc:	Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] tmpfs: truncate at i_size

On Tue, 19 May 2015, Josef Bacik wrote:

> If we fallocate past i_size with KEEP_SIZE, extend the file to use some but not
> all of this space, and then truncate(i_size) we won't trim the excess
> preallocated space.  We decided at LSF that we want to truncate the fallocated
> bit past i_size when we truncate to i_size, which is what this patch does.
> Thanks,
> 
> Signed-off-by: Josef Bacik <jbacik@...com>

Sorry for the delay, it's been on my mind but only now I get to it.
Yes, that was agreed at LSF, and I've checked that indeed tmpfs is
out of line here: thank you for fixing it.  But I do prefer your
original more explicit description, so I'll send the patch to akpm
now for v4.2, with that description instead (plus a reference to LSF).

Thanks,
Hugh

> ---
>  mm/shmem.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/mm/shmem.c b/mm/shmem.c
> index de98137..089afde 100644
> --- a/mm/shmem.c
> +++ b/mm/shmem.c
> @@ -569,7 +569,7 @@ static int shmem_setattr(struct dentry *dentry, struct iattr *attr)
>  			i_size_write(inode, newsize);
>  			inode->i_ctime = inode->i_mtime = CURRENT_TIME;
>  		}
> -		if (newsize < oldsize) {
> +		if (newsize <= oldsize) {
>  			loff_t holebegin = round_up(newsize, PAGE_SIZE);
>  			unmap_mapping_range(inode->i_mapping, holebegin, 0, 1);
>  			shmem_truncate_range(inode, newsize, (loff_t)-1);
> -- 
> 1.8.3.1
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