linux-kernel - Re: [RFC v3 02/24] fs: add frozen sb state helpers

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Message-ID: <20230116161120.fczsdy2vptgpb5z4@quack3>
Date:   Mon, 16 Jan 2023 17:11:20 +0100
From:   Jan Kara <jack@...e.cz>
To:     Luis Chamberlain <mcgrof@...nel.org>
Cc:     hch@...radead.org, djwong@...nel.org, song@...nel.org,
        rafael@...nel.org, gregkh@...uxfoundation.org,
        viro@...iv.linux.org.uk, jack@...e.cz, bvanassche@....org,
        ebiederm@...ssion.com, mchehab@...nel.org, keescook@...omium.org,
        p.raghav@...sung.com, linux-fsdevel@...r.kernel.org,
        kernel@...force.de, kexec@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC v3 02/24] fs: add frozen sb state helpers

On Fri 13-01-23 16:33:47, Luis Chamberlain wrote:
> Provide helpers so that we can check a superblock frozen state.
> This will make subsequent changes easier to read. This makes
> no functional changes.
> 
> Signed-off-by: Luis Chamberlain <mcgrof@...nel.org>

Sure. Feel free to add:

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

								Honza

> ---
>  fs/ext4/ext4_jbd2.c |  2 +-
>  fs/gfs2/sys.c       |  2 +-
>  fs/quota/quota.c    |  4 ++--
>  fs/super.c          |  4 ++--
>  fs/xfs/xfs_trans.c  |  3 +--
>  include/linux/fs.h  | 22 ++++++++++++++++++++++
>  6 files changed, 29 insertions(+), 8 deletions(-)
> 
> diff --git a/fs/ext4/ext4_jbd2.c b/fs/ext4/ext4_jbd2.c
> index 77f318ec8abb..ef441f15053b 100644
> --- a/fs/ext4/ext4_jbd2.c
> +++ b/fs/ext4/ext4_jbd2.c
> @@ -72,7 +72,7 @@ static int ext4_journal_check_start(struct super_block *sb)
>  
>  	if (sb_rdonly(sb))
>  		return -EROFS;
> -	WARN_ON(sb->s_writers.frozen == SB_FREEZE_COMPLETE);
> +	WARN_ON(sb_is_frozen(sb));
>  	journal = EXT4_SB(sb)->s_journal;
>  	/*
>  	 * Special case here: if the journal has aborted behind our
> diff --git a/fs/gfs2/sys.c b/fs/gfs2/sys.c
> index d0b80552a678..b98be03d0d1e 100644
> --- a/fs/gfs2/sys.c
> +++ b/fs/gfs2/sys.c
> @@ -146,7 +146,7 @@ static ssize_t uuid_show(struct gfs2_sbd *sdp, char *buf)
>  static ssize_t freeze_show(struct gfs2_sbd *sdp, char *buf)
>  {
>  	struct super_block *sb = sdp->sd_vfs;
> -	int frozen = (sb->s_writers.frozen == SB_UNFROZEN) ? 0 : 1;
> +	int frozen = sb_is_unfrozen(sb) ? 0 : 1;
>  
>  	return snprintf(buf, PAGE_SIZE, "%d\n", frozen);
>  }
> diff --git a/fs/quota/quota.c b/fs/quota/quota.c
> index 052f143e2e0e..d8147c21bf03 100644
> --- a/fs/quota/quota.c
> +++ b/fs/quota/quota.c
> @@ -890,13 +890,13 @@ static struct super_block *quotactl_block(const char __user *special, int cmd)
>  	sb = user_get_super(dev, excl);
>  	if (!sb)
>  		return ERR_PTR(-ENODEV);
> -	if (thawed && sb->s_writers.frozen != SB_UNFROZEN) {
> +	if (thawed && sb_is_unfrozen(sb)) {
>  		if (excl)
>  			up_write(&sb->s_umount);
>  		else
>  			up_read(&sb->s_umount);
>  		wait_event(sb->s_writers.wait_unfrozen,
> -			   sb->s_writers.frozen == SB_UNFROZEN);
> +			   sb_is_unfrozen(sb));
>  		put_super(sb);
>  		goto retry;
>  	}
> diff --git a/fs/super.c b/fs/super.c
> index a31a41b313f3..fdcf5a87af0a 100644
> --- a/fs/super.c
> +++ b/fs/super.c
> @@ -883,7 +883,7 @@ int reconfigure_super(struct fs_context *fc)
>  
>  	if (fc->sb_flags_mask & ~MS_RMT_MASK)
>  		return -EINVAL;
> -	if (sb->s_writers.frozen != SB_UNFROZEN)
> +	if (!(sb_is_unfrozen(sb)))
>  		return -EBUSY;
>  
>  	retval = security_sb_remount(sb, fc->security);
> @@ -907,7 +907,7 @@ int reconfigure_super(struct fs_context *fc)
>  			down_write(&sb->s_umount);
>  			if (!sb->s_root)
>  				return 0;
> -			if (sb->s_writers.frozen != SB_UNFROZEN)
> +			if (!sb_is_unfrozen(sb))
>  				return -EBUSY;
>  			remount_ro = !sb_rdonly(sb);
>  		}
> diff --git a/fs/xfs/xfs_trans.c b/fs/xfs/xfs_trans.c
> index 7bd16fbff534..ceb4890a4c96 100644
> --- a/fs/xfs/xfs_trans.c
> +++ b/fs/xfs/xfs_trans.c
> @@ -267,8 +267,7 @@ xfs_trans_alloc(
>  	 * Zero-reservation ("empty") transactions can't modify anything, so
>  	 * they're allowed to run while we're frozen.
>  	 */
> -	WARN_ON(resp->tr_logres > 0 &&
> -		mp->m_super->s_writers.frozen == SB_FREEZE_COMPLETE);
> +	WARN_ON(resp->tr_logres > 0 && sb_is_frozen(mp->m_super));
>  	ASSERT(!(flags & XFS_TRANS_RES_FDBLKS) ||
>  	       xfs_has_lazysbcount(mp));
>  
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index 5042f5ab74a4..c0cab61f9f9a 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -1604,6 +1604,28 @@ static inline bool sb_start_intwrite_trylock(struct super_block *sb)
>  	return __sb_start_write_trylock(sb, SB_FREEZE_FS);
>  }
>  
> +/**
> + * sb_is_frozen - is superblock frozen
> + * @sb: the super to check
> + *
> + * Returns true if the super is frozen.
> + */
> +static inline bool sb_is_frozen(struct super_block *sb)
> +{
> +	return sb->s_writers.frozen == SB_FREEZE_COMPLETE;
> +}
> +
> +/**
> + * sb_is_unfrozen - is superblock unfrozen
> + * @sb: the super to check
> + *
> + * Returns true if the super is unfrozen.
> + */
> +static inline bool sb_is_unfrozen(struct super_block *sb)
> +{
> +	return sb->s_writers.frozen == SB_UNFROZEN;
> +}
> +
>  bool inode_owner_or_capable(struct user_namespace *mnt_userns,
>  			    const struct inode *inode);
>  
> -- 
> 2.35.1
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR