linux-ext4 - Re: [PATCH V2] ext4: don't complain about incorrect features when probing

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Message-ID: <20180306110217.qq555htbpdecfjyv@quack2.suse.cz>
Date:   Tue, 6 Mar 2018 12:02:17 +0100
From:   Jan Kara <jack@...e.cz>
To:     Eric Sandeen <sandeen@...hat.com>
Cc:     "linux-ext4@...r.kernel.org" <linux-ext4@...r.kernel.org>,
        Joakim Tjernlund <Joakim.Tjernlund@...inera.com>
Subject: Re: [PATCH V2] ext4: don't complain about incorrect features when
 probing

On Fri 02-03-18 10:51:28, Eric Sandeen wrote:
> 
> 
> If mount is auto-probing for filesystem type, it will try various
> filesystems in order, with the MS_SILENT flag set.  We get
> that flag as the silent arg to ext4_fill_super.
> 
> If we're probing (silent==1) then don't complain about feature
> incompatibilities that are found if it looks like it's actually
> a different valid extN type - failed probes should be silent
> in this case.
> 
> If the on-disk features are unknown even to ext4, then complain.
> 
> Reported-by: Joakim Tjernlund <Joakim.Tjernlund@...inera.com>
> Signed-off-by: Eric Sandeen <sandeen@...hat.com>

The patch looks good. You can add:

Reviewed-by: Jan Kara <jack@...e.cz>

								Honza


> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> index b0915b7..ae40368 100644
> --- a/fs/ext4/super.c
> +++ b/fs/ext4/super.c
> @@ -3659,6 +3659,12 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
>  			ext4_msg(sb, KERN_INFO, "mounting ext2 file system "
>  				 "using the ext4 subsystem");
>  		else {
> +			/*
> +			 * If we're probing be silent, if this looks like
> +			 * it's actually an ext[34] filesystem.
> +			 */
> +			if (silent && ext4_feature_set_ok(sb, sb_rdonly(sb)))
> +				goto failed_mount;
>  			ext4_msg(sb, KERN_ERR, "couldn't mount as ext2 due "
>  				 "to feature incompatibilities");
>  			goto failed_mount;
> @@ -3670,6 +3676,12 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
>  			ext4_msg(sb, KERN_INFO, "mounting ext3 file system "
>  				 "using the ext4 subsystem");
>  		else {
> +			/*
> +			 * If we're probing be silent, if this looks like
> +			 * it's actually an ext4 filesystem.
> +			 */
> +			if (silent && ext4_feature_set_ok(sb, sb_rdonly(sb)))
> +				goto failed_mount;
>  			ext4_msg(sb, KERN_ERR, "couldn't mount as ext3 due "
>  				 "to feature incompatibilities");
>  			goto failed_mount;
> 
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR