Re: [PATCH 8/8] btrfs: remove BTRFS_INODE_READDIO_NEED_LOCK

From: Nikolay Borisov <nborisov@suse.com>
To: Goldwyn Rodrigues <rgoldwyn@suse.de>, linux-btrfs@vger.kernel.org
Cc: linux-fsdevel@vger.kernel.org, hch@infradead.org,
	darrick.wong@oracle.com, fdmanana@kernel.org, dsterba@suse.cz,
	jthumshirn@suse.de, Goldwyn Rodrigues <rgoldwyn@suse.com>
Subject: Re: [PATCH 8/8] btrfs: remove BTRFS_INODE_READDIO_NEED_LOCK
Date: Fri, 6 Dec 2019 00:57:43 +0200	[thread overview]
Message-ID: <6a7e76a4-699a-08a7-79ef-4da7c62e2ff9@suse.com> (raw)
In-Reply-To: <20191205155630.28817-9-rgoldwyn@suse.de>


On 5.12.19 г. 17:56 ч., Goldwyn Rodrigues wrote:
> From: Goldwyn Rodrigues <rgoldwyn@suse.com>
> 
> Since we now perform direct reads using i_rwsem, we can remove this
> inode flag used to co-ordinate unlocked reads.
> 
> Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>

Truncate call chain is

do_truncate <-- calls inode_lock
  notify_change
   ->setattr/btrfs_setattr
     btrfs_setsize

So :

Reviewed-by: Nikolay Borisov <nborisov@suse.com>

> ---
>  fs/btrfs/btrfs_inode.h | 18 ------------------
>  fs/btrfs/inode.c       |  5 -----
>  2 files changed, 23 deletions(-)
> 
> diff --git a/fs/btrfs/btrfs_inode.h b/fs/btrfs/btrfs_inode.h
> index f853835c409c..31c327666a61 100644
> --- a/fs/btrfs/btrfs_inode.h
> +++ b/fs/btrfs/btrfs_inode.h
> @@ -27,7 +27,6 @@ enum {
>  	BTRFS_INODE_NEEDS_FULL_SYNC,
>  	BTRFS_INODE_COPY_EVERYTHING,
>  	BTRFS_INODE_IN_DELALLOC_LIST,
> -	BTRFS_INODE_READDIO_NEED_LOCK,
>  	BTRFS_INODE_HAS_PROPS,
>  	BTRFS_INODE_SNAPSHOT_FLUSH,
>  };
> @@ -320,23 +319,6 @@ struct btrfs_dio_private {
>  			blk_status_t);
>  };
>  
> -/*
> - * Disable DIO read nolock optimization, so new dio readers will be forced
> - * to grab i_mutex. It is used to avoid the endless truncate due to
> - * nonlocked dio read.
> - */
> -static inline void btrfs_inode_block_unlocked_dio(struct btrfs_inode *inode)
> -{
> -	set_bit(BTRFS_INODE_READDIO_NEED_LOCK, &inode->runtime_flags);
> -	smp_mb();
> -}
> -
> -static inline void btrfs_inode_resume_unlocked_dio(struct btrfs_inode *inode)
> -{
> -	smp_mb__before_atomic();
> -	clear_bit(BTRFS_INODE_READDIO_NEED_LOCK, &inode->runtime_flags);
> -}
> -
>  /* Array of bytes with variable length, hexadecimal format 0x1234 */
>  #define CSUM_FMT				"0x%*phN"
>  #define CSUM_FMT_VALUE(size, bytes)		size, bytes
> diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
> index fedbbcf108cf..71ba4b5503f0 100644
> --- a/fs/btrfs/inode.c
> +++ b/fs/btrfs/inode.c
> @@ -5238,11 +5238,6 @@ static int btrfs_setsize(struct inode *inode, struct iattr *attr)
>  
>  		truncate_setsize(inode, newsize);
>  
> -		/* Disable nonlocked read DIO to avoid the endless truncate */
> -		btrfs_inode_block_unlocked_dio(BTRFS_I(inode));
> -		inode_dio_wait(inode);
> -		btrfs_inode_resume_unlocked_dio(BTRFS_I(inode));
> -
>  		ret = btrfs_truncate(inode, newsize == oldsize);
>  		if (ret && inode->i_nlink) {
>  			int err;
>