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Date:   Tue, 3 Jan 2023 11:27:40 +0100
From:   Jan Kara <jack@suse.cz>
To:     zhanchengbin <zhanchengbin1@huawei.com>
Cc:     tytso@mit.edu, jack@suse.com, linux-ext4@vger.kernel.org,
        yi.zhang@huawei.com, yebin10@huawei.com, linfeilong@huawei.com,
        liuzhiqiang26@huawei.com
Subject: Re: [PATCH] ext4: fix inode tree inconsistency caused by ENOMEM
Message-ID: <20230103102740.y2dvtif4gdbmrbg2@quack3>
References: <20230103022812.130603-1-zhanchengbin1@huawei.com>
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On Tue 03-01-23 10:28:12, zhanchengbin wrote:
> If ENOMEM fails when the extent is splitting, we need to restore the length
> of the split extent.
> In the ext4_split_extent_at function, only in ext4_ext_create_new_leaf will
> it alloc memory and change the shape of the extent tree,even if an ENOMEM
> is returned at this time, the extent tree is still self-consistent, Just
> restore the split extent lens in the function ext4_split_extent_at.
> 
> ext4_split_extent_at
>  ext4_ext_insert_extent
>   ext4_ext_create_new_leaf
>    1)ext4_ext_split
>      ext4_find_extent
>    2)ext4_ext_grow_indepth
>      ext4_find_extent
> 
> Signed-off-by: zhanchengbin <zhanchengbin1@huawei.com>

Yeah that should work. Feel free to add:

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

								Honza

> ---
>  Another solution is to add the __GFP_NOFAIL flag when allocating memory.
> 
>  fs/ext4/extents.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
> index 9de1c9d1a13d..3559ea6b0781 100644
> --- a/fs/ext4/extents.c
> +++ b/fs/ext4/extents.c
> @@ -3251,7 +3251,7 @@ static int ext4_split_extent_at(handle_t *handle,
>  		ext4_ext_mark_unwritten(ex2);
>  
>  	err = ext4_ext_insert_extent(handle, inode, ppath, &newex, flags);
> -	if (err != -ENOSPC && err != -EDQUOT)
> +	if (err != -ENOSPC && err != -EDQUOT && err != -ENOMEM)
>  		goto out;
>  
>  	if (EXT4_EXT_MAY_ZEROOUT & split_flag) {
> -- 
> 2.31.1
> 
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR