linux-ext4 - Re: [PATCH v3 3/6] ext4: mark inode dirty before grabbing i_data_sem in ext4

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Message-ID: <20220427160206.icjjrhqlsf42bega@quack3.lan>
Date:   Wed, 27 Apr 2022 18:02:06 +0200
From:   Jan Kara <jack@...e.cz>
To:     Harshad Shirwadkar <harshadshirwadkar@...il.com>
Cc:     linux-ext4@...r.kernel.org, riteshh@...ux.ibm.com, jack@...e.cz,
        tytso@....edu
Subject: Re: [PATCH v3 3/6] ext4: mark inode dirty before grabbing i_data_sem
 in ext4_setattr

On Tue 19-04-22 10:31:40, Harshad Shirwadkar wrote:
> From: Harshad Shirwadkar <harshadshirwadkar@...il.com>
> 
> Mark inode dirty first and then grab i_data_sem in ext4_setattr().
> 
> Signed-off-by: Harshad Shirwadkar <harshadshirwadkar@...il.com>

> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index e88940251afd..6eae0804c6fd 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -5455,11 +5455,12 @@ int ext4_setattr(struct user_namespace *mnt_userns, struct dentry *dentry,
>  					(attr->ia_size > 0 ? attr->ia_size - 1 : 0) >>
>  					inode->i_sb->s_blocksize_bits);
>  
> -			down_write(&EXT4_I(inode)->i_data_sem);
> -			EXT4_I(inode)->i_disksize = attr->ia_size;
>  			rc = ext4_mark_inode_dirty(handle, inode);
>  			if (!error)
>  				error = rc;
> +			down_write(&EXT4_I(inode)->i_data_sem);
> +			EXT4_I(inode)->i_disksize = attr->ia_size;
> +

Hum, this isn't going to fly because ext4_mark_inode_dirty() copies data
from ext4_inode_info to the on-disk buffer and thus new i_disksize will not
be stored on the disk after your change.

								Honza

-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR