linux-kernel - Re: [PATCH v2 1/1] ftruncate, truncate: create fanotify events

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Date:	Fri, 14 Nov 2014 22:30:40 +0100
From:	Heinrich Schuchardt <xypron.glpk@....de>
To:	Jan Kara <jack@...e.cz>
CC:	Christoph Hellwig <hch@...radead.org>,
	Eric Paris <eparis@...isplace.org>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>,
	Jeff Layton <jlayton@...chiereds.net>,
	"J. Bruce Fields" <bfields@...ldses.org>,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/1] ftruncate, truncate: create fanotify events

Hello Jan,

thank you for the review.

On 14.11.2014 11:01, Jan Kara wrote:
>>
>> We only want to create FAN_MODIFY events for ATTR_SIZE. So only for
>> these events we need a path.
>>
>> To my knowledge notify_change is called with ATTR_SIZE from
>> do_truncate(), ecryptfs_truncate() and will be called with ATTR_SIZE
>> from ovl_setattr() for a truncation.
>    There's also a call in fs/cachefiles/interface.c: cachefiles_attr_changed()
> and fs/hpfs/namei.c: hpfs_unlink() and nfs plays with ATTR_SIZE although I
> wasn't able to track down whether it actually passes it to notify_change().

cachefiles_attr_changed() contains two calls to notify_change(). Both 
calls pass ATTR_SIZE as sole attribute.

In cachefiles_attr_changed() we can create a path object with
path.dentry = object->backer;
path.mnt = cache->mnt;

In hpfs_unlink() a truncation occurs only if deletion fails.
I do not see how to access a path here.

notify_change() is not called in directory fs/nfs.
grep -GHrn notify_change fs/nfs/
This does not test for any indirect call.

Best regards

Heinrich Schuchardt


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