linux-ext4 - Re: [PATCH v3 1/3] ext4: fix setattr project check upon fssetxattr ioctl

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Date:   Sat, 15 Sep 2018 23:55:29 -0400
From:   "Theodore Y. Ts'o" <tytso@....edu>
To:     Wang Shilong <wangshilong1991@...il.com>
Cc:     linux-ext4@...r.kernel.org, linux-f2fs-devel@...ts.sourceforge.net,
        dchinner@...hat.com, adilger@...ger.ca, wshilong@....com
Subject: Re: [PATCH v3 1/3] ext4: fix setattr project check upon fssetxattr
 ioctl

On Wed, Sep 12, 2018 at 08:57:16AM +0900, Wang Shilong wrote:
> diff --git a/fs/ext4/ioctl.c b/fs/ext4/ioctl.c
> index a7074115d6f6..f81102bd3203 100644
> --- a/fs/ext4/ioctl.c
> +++ b/fs/ext4/ioctl.c
> @@ -339,19 +339,14 @@ static int ext4_ioctl_setproject(struct file *filp, __u32 projid)
>  	if (projid_eq(kprojid, EXT4_I(inode)->i_projid))
>  		return 0;
>  
> -	err = mnt_want_write_file(filp);
> -	if (err)
> -		return err;
> -

A huge part of this patch is dropping the calls to
mnt_want_write_file() and mnt_drop_write_file().  What's the
justification for doing this?  The use of mnt_want_write_file() looks
necessary to me...

				- Ted