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Subject: Re: [PATCH] ext4: fix reading leftover inlined symlinks
To:     <openglfreak@googlemail.com>
CC:     <tytso@mit.edu>, <adilger.kernel@dilger.ca>, <jack@suse.cz>,
        <yukuai3@huawei.com>, <linux-ext4@vger.kernel.org>
References: <20220630090100.2769490-1-yi.zhang@huawei.com>
From:   Zhang Yi <yi.zhang@huawei.com>
Message-ID: <b1f7a565-1128-f6f3-1775-8aac079b833b@huawei.com>
Date:   Thu, 30 Jun 2022 16:51:41 +0800
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Hi, Torge.

Please take a look at this patch and check could it solve your problem or not.

Thanks,
Yi.

On 2022/6/30 17:01, Zhang Yi wrote:
> Since commit 6493792d3299 ("ext4: convert symlink external data block
> mapping to bdev"), create new symlink with inline_data is not supported,
> but it missing to handle the leftover inlined symlinks, which could
> cause below error message and fail to read symlink.
> 
>  ls: cannot read symbolic link 'foo': Structure needs cleaning
> 
>  EXT4-fs error (device sda): ext4_map_blocks:605: inode #12: block
>  2021161080: comm ls: lblock 0 mapped to illegal pblock 2021161080
>  (length 1)
> 
> Fix this regression by adding ext4_read_inline_link(), which read the
> inline data directly and convert it through a kmalloced buffer.
> 
> Fixes: 6493792d3299 ("ext4: convert symlink external data block mapping to bdev")
> Reported-by: Torge Matthies <openglfreak@googlemail.com>
> Signed-off-by: Zhang Yi <yi.zhang@huawei.com>
> ---
>  fs/ext4/ext4.h    |  1 +
>  fs/ext4/inline.c  | 30 ++++++++++++++++++++++++++++++
>  fs/ext4/symlink.c | 15 +++++++++++++++
>  3 files changed, 46 insertions(+)
> 
> diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
> index 75b8d81b2469..adfc30ee4b7b 100644
> --- a/fs/ext4/ext4.h
> +++ b/fs/ext4/ext4.h
> @@ -3583,6 +3583,7 @@ extern struct buffer_head *ext4_get_first_inline_block(struct inode *inode,
>  extern int ext4_inline_data_fiemap(struct inode *inode,
>  				   struct fiemap_extent_info *fieinfo,
>  				   int *has_inline, __u64 start, __u64 len);
> +extern void *ext4_read_inline_link(struct inode *inode);
>  
>  struct iomap;
>  extern int ext4_inline_data_iomap(struct inode *inode, struct iomap *iomap);
> diff --git a/fs/ext4/inline.c b/fs/ext4/inline.c
> index cff52ff6549d..1fa36cbe09ec 100644
> --- a/fs/ext4/inline.c
> +++ b/fs/ext4/inline.c
> @@ -6,6 +6,7 @@
>  
>  #include <linux/iomap.h>
>  #include <linux/fiemap.h>
> +#include <linux/namei.h>
>  #include <linux/iversion.h>
>  #include <linux/sched/mm.h>
>  
> @@ -1588,6 +1589,35 @@ int ext4_read_inline_dir(struct file *file,
>  	return ret;
>  }
>  
> +void *ext4_read_inline_link(struct inode *inode)
> +{
> +	struct ext4_iloc iloc;
> +	int ret, inline_size;
> +	void *link;
> +
> +	ret = ext4_get_inode_loc(inode, &iloc);
> +	if (ret)
> +		return ERR_PTR(ret);
> +
> +	ret = -ENOMEM;
> +	inline_size = ext4_get_inline_size(inode);
> +	link = kmalloc(inline_size + 1, GFP_NOFS);
> +	if (!link)
> +		goto out;
> +
> +	ret = ext4_read_inline_data(inode, link, inline_size, &iloc);
> +	if (ret < 0) {
> +		kfree(link);
> +		goto out;
> +	}
> +	nd_terminate_link(link, inode->i_size, ret);
> +out:
> +	if (ret < 0)
> +		link = ERR_PTR(ret);
> +	brelse(iloc.bh);
> +	return link;
> +}
> +
>  struct buffer_head *ext4_get_first_inline_block(struct inode *inode,
>  					struct ext4_dir_entry_2 **parent_de,
>  					int *retval)
> diff --git a/fs/ext4/symlink.c b/fs/ext4/symlink.c
> index d281f5bcc526..3d3ed3c38f56 100644
> --- a/fs/ext4/symlink.c
> +++ b/fs/ext4/symlink.c
> @@ -74,6 +74,21 @@ static const char *ext4_get_link(struct dentry *dentry, struct inode *inode,
>  				 struct delayed_call *callback)
>  {
>  	struct buffer_head *bh;
> +	char *inline_link;
> +
> +	/*
> +	 * Create a new inlined symlink is not supported, just provide a
> +	 * method to read the leftovers.
> +	 */
> +	if (ext4_has_inline_data(inode)) {
> +		if (!dentry)
> +			return ERR_PTR(-ECHILD);
> +
> +		inline_link = ext4_read_inline_link(inode);
> +		if (!IS_ERR(inline_link))
> +			set_delayed_call(callback, kfree_link, inline_link);
> +		return inline_link;
> +	}
>  
>  	if (!dentry) {
>  		bh = ext4_getblk(NULL, inode, 0, EXT4_GET_BLOCKS_CACHED_NOWAIT);
>