linux-kernel - Re: [PATCH 8/9] Revert "ext4: avoid deadlocks in the writeback path by using sb_getblk

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Message-ID: <20161216084126.GF26608@quack2.suse.cz>
Date:   Fri, 16 Dec 2016 09:41:26 +0100
From:   Jan Kara <jack@...e.cz>
To:     Michal Hocko <mhocko@...nel.org>
Cc:     linux-mm@...ck.org, linux-fsdevel@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Dave Chinner <david@...morbit.com>,
        Theodore Ts'o <tytso@....edu>, Chris Mason <clm@...com>,
        David Sterba <dsterba@...e.cz>, Jan Kara <jack@...e.cz>,
        ceph-devel@...r.kernel.org, cluster-devel@...hat.com,
        linux-nfs@...r.kernel.org, logfs@...fs.org,
        linux-xfs@...r.kernel.org, linux-ext4@...r.kernel.org,
        linux-btrfs@...r.kernel.org, linux-mtd@...ts.infradead.org,
        reiserfs-devel@...r.kernel.org,
        linux-ntfs-dev@...ts.sourceforge.net,
        linux-f2fs-devel@...ts.sourceforge.net,
        linux-afs@...ts.infradead.org, LKML <linux-kernel@...r.kernel.org>,
        Michal Hocko <mhocko@...e.com>
Subject: Re: [PATCH 8/9] Revert "ext4: avoid deadlocks in the writeback path
 by using sb_getblk_gfp"

On Thu 15-12-16 15:07:14, Michal Hocko wrote:
> From: Michal Hocko <mhocko@...e.com>
> 
> This reverts commit c45653c341f5c8a0ce19c8f0ad4678640849cb86 because
> sb_getblk_gfp is not really needed as
> sb_getblk
>   __getblk_gfp
>     __getblk_slow
>       grow_buffers
>         grow_dev_page
> 	  gfp_mask = mapping_gfp_constraint(inode->i_mapping, ~__GFP_FS) | gfp
> 
> so __GFP_FS is cleared unconditionally and therefore the above commit
> didn't have any real effect in fact.
> 
> This patch should not introduce any functional change. The main point
> of this change is to reduce explicit GFP_NOFS usage inside ext4 code to
> make the review of the remaining usage easier.
> 
> Signed-off-by: Michal Hocko <mhocko@...e.com>

Looks good to me. You can add:

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

								Honza

> ---
>  fs/ext4/extents.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
> index b1f8416923ab..ef815eb72389 100644
> --- a/fs/ext4/extents.c
> +++ b/fs/ext4/extents.c
> @@ -518,7 +518,7 @@ __read_extent_tree_block(const char *function, unsigned int line,
>  	struct buffer_head		*bh;
>  	int				err;
>  
> -	bh = sb_getblk_gfp(inode->i_sb, pblk, __GFP_MOVABLE | GFP_NOFS);
> +	bh = sb_getblk(inode->i_sb, pblk);
>  	if (unlikely(!bh))
>  		return ERR_PTR(-ENOMEM);
>  
> @@ -1096,7 +1096,7 @@ static int ext4_ext_split(handle_t *handle, struct inode *inode,
>  		err = -EFSCORRUPTED;
>  		goto cleanup;
>  	}
> -	bh = sb_getblk_gfp(inode->i_sb, newblock, __GFP_MOVABLE | GFP_NOFS);
> +	bh = sb_getblk(inode->i_sb, newblock);
>  	if (unlikely(!bh)) {
>  		err = -ENOMEM;
>  		goto cleanup;
> @@ -1290,7 +1290,7 @@ static int ext4_ext_grow_indepth(handle_t *handle, struct inode *inode,
>  	if (newblock == 0)
>  		return err;
>  
> -	bh = sb_getblk_gfp(inode->i_sb, newblock, __GFP_MOVABLE | GFP_NOFS);
> +	bh = sb_getblk(inode->i_sb, newblock);
>  	if (unlikely(!bh))
>  		return -ENOMEM;
>  	lock_buffer(bh);
> -- 
> 2.10.2
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR