From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wi0-f181.google.com (mail-wi0-f181.google.com [209.85.212.181]) by kanga.kvack.org (Postfix) with ESMTP id 9AE836B0038 for ; Tue, 16 Jun 2015 16:10:07 -0400 (EDT) Received: by wiga1 with SMTP id a1so119121716wig.0 for ; Tue, 16 Jun 2015 13:10:07 -0700 (PDT) Received: from mail-wg0-x231.google.com (mail-wg0-x231.google.com. [2a00:1450:400c:c00::231]) by mx.google.com with ESMTPS id by11si4809159wib.105.2015.06.16.13.10.05 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 16 Jun 2015 13:10:06 -0700 (PDT) Received: by wgzl5 with SMTP id l5so20290335wgz.3 for ; Tue, 16 Jun 2015 13:10:05 -0700 (PDT) Date: Tue, 16 Jun 2015 13:07:04 -0700 (PDT) From: Hugh Dickins Subject: [PATCH] tmpfs: truncate prealloc blocks past i_size In-Reply-To: Message-ID: References: <1432049251-3298-1-git-send-email-jbacik@fb.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: Josef Bacik , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org From: Josef Bacik One of the rocksdb people noticed that when you do something like this fallocate(fd, FALLOC_FL_KEEP_SIZE, 0, 10M) pwrite(fd, buf, 5M, 0) ftruncate(5M) on tmpfs, the file would still take up 10M: which led to super fun issues because we were getting ENOSPC before we thought we should be getting ENOSPC. This patch fixes the problem, and mirrors what all the other fs'es do (and was agreed to be the correct behaviour at LSF). I tested it locally to make sure it worked properly with the following xfs_io -f -c "falloc -k 0 10M" -c "pwrite 0 5M" -c "truncate 5M" file Without the patch we have "Blocks: 20480", with the patch we have the correct value of "Blocks: 10240". Signed-off-by: Josef Bacik Signed-off-by: Hugh Dickins --- mm/shmem.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- 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 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org