linux-kernel - Re: [PATCH 5/9] ext4: don't access the source subdirectory content on same-directory rename

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Message-ID: <20231123093112.rkgqmyaocisvyeyh@quack3>
Date:   Thu, 23 Nov 2023 10:31:12 +0100
From:   Jan Kara <jack@...e.cz>
To:     Al Viro <viro@...iv.linux.org.uk>
Cc:     linux-fsdevel@...r.kernel.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Mo Zou <lostzoumo@...il.com>, Jan Kara <jack@...e.cz>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 5/9] ext4: don't access the source subdirectory content
 on same-directory rename

On Wed 22-11-23 19:36:48, Al Viro wrote:
> We can't really afford locking the source on same-directory rename;
> currently vfs_rename() tries to do that, but it will have to be changed.
> The logics in ext4 is lazy and goes looking for ".." in source even in
> same-directory case.  It's not hard to get rid of that, leaving that
> behaviour only for cross-directory case; that VFS can get locks safely
> (and will keep doing that after the coming changes).
> 
> Signed-off-by: Al Viro <viro@...iv.linux.org.uk>

Looks good to me. Feel free to add:

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

								Honza

> ---
>  fs/ext4/namei.c | 21 +++++++++++++--------
>  1 file changed, 13 insertions(+), 8 deletions(-)
> 
> diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
> index d252935f9c8a..467ba47a691c 100644
> --- a/fs/ext4/namei.c
> +++ b/fs/ext4/namei.c
> @@ -3591,10 +3591,14 @@ struct ext4_renament {
>  	int dir_inlined;
>  };
>  
> -static int ext4_rename_dir_prepare(handle_t *handle, struct ext4_renament *ent)
> +static int ext4_rename_dir_prepare(handle_t *handle, struct ext4_renament *ent, bool is_cross)
>  {
>  	int retval;
>  
> +	ent->is_dir = true;
> +	if (!is_cross)
> +		return 0;
> +
>  	ent->dir_bh = ext4_get_first_dir_block(handle, ent->inode,
>  					      &retval, &ent->parent_de,
>  					      &ent->dir_inlined);
> @@ -3612,6 +3616,9 @@ static int ext4_rename_dir_finish(handle_t *handle, struct ext4_renament *ent,
>  {
>  	int retval;
>  
> +	if (!ent->dir_bh)
> +		return 0;
> +
>  	ent->parent_de->inode = cpu_to_le32(dir_ino);
>  	BUFFER_TRACE(ent->dir_bh, "call ext4_handle_dirty_metadata");
>  	if (!ent->dir_inlined) {
> @@ -3900,7 +3907,7 @@ static int ext4_rename(struct mnt_idmap *idmap, struct inode *old_dir,
>  			if (new.dir != old.dir && EXT4_DIR_LINK_MAX(new.dir))
>  				goto end_rename;
>  		}
> -		retval = ext4_rename_dir_prepare(handle, &old);
> +		retval = ext4_rename_dir_prepare(handle, &old, new.dir != old.dir);
>  		if (retval)
>  			goto end_rename;
>  	}
> @@ -3964,7 +3971,7 @@ static int ext4_rename(struct mnt_idmap *idmap, struct inode *old_dir,
>  	}
>  	inode_set_mtime_to_ts(old.dir, inode_set_ctime_current(old.dir));
>  	ext4_update_dx_flag(old.dir);
> -	if (old.dir_bh) {
> +	if (old.is_dir) {
>  		retval = ext4_rename_dir_finish(handle, &old, new.dir->i_ino);
>  		if (retval)
>  			goto end_rename;
> @@ -3987,7 +3994,7 @@ static int ext4_rename(struct mnt_idmap *idmap, struct inode *old_dir,
>  	if (unlikely(retval))
>  		goto end_rename;
>  
> -	if (S_ISDIR(old.inode->i_mode)) {
> +	if (old.is_dir) {
>  		/*
>  		 * We disable fast commits here that's because the
>  		 * replay code is not yet capable of changing dot dot
> @@ -4114,14 +4121,12 @@ static int ext4_cross_rename(struct inode *old_dir, struct dentry *old_dentry,
>  		ext4_handle_sync(handle);
>  
>  	if (S_ISDIR(old.inode->i_mode)) {
> -		old.is_dir = true;
> -		retval = ext4_rename_dir_prepare(handle, &old);
> +		retval = ext4_rename_dir_prepare(handle, &old, new.dir != old.dir);
>  		if (retval)
>  			goto end_rename;
>  	}
>  	if (S_ISDIR(new.inode->i_mode)) {
> -		new.is_dir = true;
> -		retval = ext4_rename_dir_prepare(handle, &new);
> +		retval = ext4_rename_dir_prepare(handle, &new, new.dir != old.dir);
>  		if (retval)
>  			goto end_rename;
>  	}
> -- 
> 2.39.2
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR