linux-kernel - Re: [PATCH] f2fs: fix to remove F2FS_COMPR_FL and tag F2FS_NOCOMP

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Message-ID: <YsT6LKtTQCuOdPHt@liuchao-VM>
Date:   Wed, 6 Jul 2022 10:57:48 +0800
From:   Chao Liu <chaoliu719@...il.com>
To:     Chao Yu <chao@...nel.org>, Jaegeuk Kim <jaegeuk@...nel.org>
Cc:     linux-f2fs-devel@...ts.sourceforge.net,
        linux-kernel@...r.kernel.org, Yue Hu <huyue2@...lpad.com>,
        Wayne Zhang <zhangwen@...lpad.com>,
        Xiaoyu Qi <qxy65535@...il.com>, Chao Liu <liuchao@...lpad.com>
Subject: Re: [PATCH] f2fs: fix to remove F2FS_COMPR_FL and tag F2FS_NOCOMP_FL
 at the same time

Ping.

On Thu, Jun 23, 2022 at 12:44:40PM +0800, Chao Liu wrote:
> On Wed, Jun 22, 2022 at 09:42:13PM +0800, Chao Yu wrote:
> > On 2022/6/21 14:48, Chao Liu wrote:
> > > From: Chao Liu <liuchao@...lpad.com>
> > >
> > > If the inode has the compress flag, it will fail to use
> > > 'chattr -c +m' to remove its compress flag and tag no compress flag.
> > > However, the same command will be successful when executed again,
> > > as shown below:
> > >
> > >    $ touch foo.txt
> > >    $ chattr +c foo.txt
> > >    $ chattr -c +m foo.txt
> > >    chattr: Invalid argument while setting flags on foo.txt
> > >    $ chattr -c +m foo.txt
> > >    $ f2fs_io getflags foo.txt
> > >    get a flag on foo.txt ret=0, flags=nocompression,inline_data
> > >
> > > Fix this by removing some checks in f2fs_setflags_common()
> > > that do not affect the original logic. I go through all the
> > > possible scenarios, and the results are as follows. Bold is
> > > the only thing that has changed.
> > >
> > > +---------------+-----------+-----------+----------+
> > > |               |            file flags            |
> > > + command       +-----------+-----------+----------+
> > > |               | no flag   | compr     | nocompr  |
> > > +---------------+-----------+-----------+----------+
> > > | chattr +c     | compr     | compr     | -EINVAL  |
> > > | chattr -c     | no flag   | no flag   | nocompr  |
> > > | chattr +m     | nocompr   | -EINVAL   | nocompr  |
> > > | chattr -m     | no flag   | compr     | no flag  |
> > > | chattr +c +m  | -EINVAL   | -EINVAL   | -EINVAL  |
> > > | chattr +c -m  | compr     | compr     | compr    |
> > > | chattr -c +m  | nocompr   | *nocompr* | nocompr  |
> > > | chattr -c -m  | no flag   | no flag   | no flag  |
> > > +---------------+-----------+-----------+----------+
> > >
> > > Fixes: 4c8ff7095bef ("f2fs: support data compression")
> > > Signed-off-by: Chao Liu <liuchao@...lpad.com>
> > > ---
> > >
> > > This patch depends on the the patch
> > > "f2fs: allow compression of files without blocks" sent earlier this day.
> > >
> > >   fs/f2fs/file.c | 9 +--------
> > >   1 file changed, 1 insertion(+), 8 deletions(-)
> > >
> > > diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> > > index daaa0dfd2d2e..0c3ae5993b7a 100644
> > > --- a/fs/f2fs/file.c
> > > +++ b/fs/f2fs/file.c
> > > @@ -1873,10 +1873,7 @@ static int f2fs_setflags_common(struct inode *inode, u32 iflags, u32 mask)
> > >   		if (masked_flags & F2FS_COMPR_FL) {
> > >   			if (!f2fs_disable_compressed_file(inode))
> > >   				return -EINVAL;
> > > -		}
> > > -		if (iflags & F2FS_NOCOMP_FL)
> > > -			return -EINVAL;
> > > -		if (iflags & F2FS_COMPR_FL) {
> > > +		} else {
> > >   			if (!f2fs_may_compress(inode))
> > >   				return -EINVAL;
> > >   			if (S_ISREG(inode->i_mode) && F2FS_HAS_BLOCKS(inode))
> > > @@ -1885,10 +1882,6 @@ static int f2fs_setflags_common(struct inode *inode, u32 iflags, u32 mask)
> > >   			set_compress_context(inode);
> > >   		}
> > >   	}
> > > -	if ((iflags ^ masked_flags) & F2FS_NOCOMP_FL) {
> > > -		if (masked_flags & F2FS_COMPR_FL)
> > > -			return -EINVAL;
> > > -	}
> >
> > Without above check condition, can we return -EINVAL for the case:
> >
> > chattr +c on file w/ nocompr flag
> >
> > |               | no flag   | compr     | nocompr  |
> > +---------------+-----------+-----------+----------+
> > | chattr +c     | compr     | compr     | *-EINVAL*  |
>
> Yes, we can.
>
> chattr(1) grabs flags via GETFLAGS, modifies the result,
> and passes that to SETFLAGS. If we execute 'chattr +c'
> on the file with nocompr flag, the iflags will
> contain both compr and nocompr flags, then be refused by:
>
>     if ((iflags & F2FS_COMPR_FL) && (iflags & F2FS_NOCOMP_FL))
>         return -EINVAL;
>
> In addition, if iflags has only compr flag, while masked_flags
> has only nocompr flag for some reason
> (either because of concurrency of chattr(1) or by a user),
> I think we need remove nocompr flag and tag compr flag on the file,
> similar to the following.
>
> |               | no flag   | compr     | nocompr  |
> +---------------+-----------+-----------+----------+
> | chattr +c -m  | compr     | compr     | *compr*  |
>
> Thanks,