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From:   Andreas Dilger <adilger@dilger.ca>
Message-Id: <934F58B9-2275-4AFB-9244-895A26249141@dilger.ca>
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Subject: Re: [PATCH] ext4: do not commit super on read-only bdev
Date:   Wed, 18 Mar 2020 16:09:11 -0600
In-Reply-To: <4b6e774d-cc00-3469-7abb-108eb151071a@sandeen.net>
Cc:     "linux-ext4@vger.kernel.org" <linux-ext4@vger.kernel.org>,
        Ritesh Harjani <riteshh@linux.ibm.com>
To:     Eric Sandeen <sandeen@sandeen.net>
References: <4b6e774d-cc00-3469-7abb-108eb151071a@sandeen.net>
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On Mar 18, 2020, at 1:19 PM, Eric Sandeen <sandeen@sandeen.net> wrote:
>=20
> From: Eric Sandeen <sandeen@redhat.com>
>=20
> Under some circumstances we may encounter a filesystem error on a
> read-only block device, and if we try to save the error info to the
> superblock and commit it, we'll wind up with a noisy error and
> backtrace, i.e.:
>=20
> [ 3337.146838] EXT4-fs error (device pmem1p2): =
ext4_get_journal_inode:4634: comm mount: inode #0: comm mount: iget: =
illegal inode #
> ------------[ cut here ]------------
> generic_make_request: Trying to write to read-only block-device =
pmem1p2 (partno 2)
> WARNING: CPU: 107 PID: 115347 at block/blk-core.c:788 =
generic_make_request_checks+0x6b4/0x7d0
> ...
>=20
> To avoid this, commit the error info in the superblock only if the
> block device is writable.
>=20
> Reported-by: Ritesh Harjani <riteshh@linux.ibm.com>
> Signed-off-by: Eric Sandeen <sandeen@redhat.com>

Reviewed-by: Andreas Dilger <adilger@dilger.ca>

> ---
>=20
> (compile-tested only FWIW)
> (also, not sure if the bdev test in __save_error_info should be =
removed?)
>=20
> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> index 0c7c4adb664e..55392903bda5 100644
> --- a/fs/ext4/super.c
> +++ b/fs/ext4/super.c
> @@ -372,7 +372,8 @@ static void save_error_info(struct super_block =
*sb, const char *func,
> 			    unsigned int line)
> {
> 	__save_error_info(sb, func, line);
> -	ext4_commit_super(sb, 1);
> +	if (!bdev_read_only(sb->s_bdev))
> +		ext4_commit_super(sb, 1);
> }
>=20
> /*


Cheers, Andreas


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