linux-kernel - Re: [f2fs-dev] [PATCH] f2fs: fix fileattr

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Message-ID: <AM6PR10MB2838705554FCB6ACE86F12BBFA5F9@AM6PR10MB2838.EURPRD10.PROD.OUTLOOK.COM>
Date:   Tue, 25 Jan 2022 22:01:49 +0000
From:   Harry Austen <harryausten@...mail.co.uk>
To:     Harry Austen <harryausten@...mail.co.uk>,
        Eric Biggers <ebiggers@...nel.org>
Cc:     linux-f2fs-devel@...ts.sourceforge.net, jaegeuk@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [f2fs-dev] [PATCH] f2fs: fix fileattr_set unsupported attribute handling

On Monday, 24 January 2022 19:25:44 GMT Eric Biggers wrote:
> On Sat, Jan 22, 2022 at 12:59:03PM +0000, Harry Austen wrote:
> > FS_IOC_SETFLAGS ioctl should return EOPNOTSUPP if the file attribute
> > (e.g. FS_NOCOW_FL) is not supported, rather than silently ignoring it
> > and returning success.
> > 
> > Fixes: 9b1bb01c8ae7 (f2fs: convert to fileattr)
> > Signed-off-by: Harry Austen <harryausten@...mail.co.uk>
> > ---
> > 
> >  fs/f2fs/file.c | 3 +--
> >  1 file changed, 1 insertion(+), 2 deletions(-)
> > 
> > diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> > index 92ec2699bc85..061bf35c2582 100644
> > --- a/fs/f2fs/file.c
> > +++ b/fs/f2fs/file.c
> > @@ -3085,9 +3085,8 @@ int f2fs_fileattr_set(struct user_namespace
> > *mnt_userns,> 
> >  		return -EIO;
> >  	
> >  	if (!f2fs_is_checkpoint_ready(F2FS_I_SB(inode)))
> >  	
> >  		return -ENOSPC;
> > 
> > -	if (fsflags & ~F2FS_GETTABLE_FS_FL)
> > +	if (fsflags & ~F2FS_SETTABLE_FS_FL)
> > 
> >  		return -EOPNOTSUPP;
> > 
> > -	fsflags &= F2FS_SETTABLE_FS_FL;
> > 
> >  	if (!fa->flags_valid)
> >  	
> >  		mask &= FS_COMMON_FL;
> 
> This is intentional, and matches what ext4 does; see the comment in the ext4
> implementation of this:
> 
>         /*
>          * chattr(1) grabs flags via GETFLAGS, modifies the result and
>          * passes that to SETFLAGS. So we cannot easily make SETFLAGS
>          * more restrictive than just silently masking off visible but
>          * not settable flags as we always did.
>          */

Ah, my apologies. I thought it looked a little too obvious. Clearly I
should have looked at the ext4 code. Please disregard this patch.

Is there anything else that could be done to improve unsettable
attribute handling? For example, is there a reason FS_NOCOW_FL is
gettable but not settable? Could it be added to the settable list?

> 
> Also, even if this patch was correct, the Fixes tag is wrong.

Having looked at this a bit more, I assume you are saying this due to
the missing double quotes around the commit summary? (just so I know for
next time as this is my first attempt at sending a kernel patch)

> 
> - Eric

Many thanks for your help Eric,
Harry