linux-kernel - Re: [PATCH v2 6/8] tmpfs: Add flag FS_CASEFOLD

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Message-ID: <87jzfshfwn.fsf@mailhost.krisman.be>
Date: Tue, 03 Sep 2024 12:15:52 -0400
From: Gabriel Krisman Bertazi <krisman@...e.de>
To: André Almeida <andrealmeid@...lia.com>
Cc: Hugh Dickins <hughd@...gle.com>,  Andrew Morton
 <akpm@...ux-foundation.org>,  Alexander Viro <viro@...iv.linux.org.uk>,
  Christian Brauner <brauner@...nel.org>,  Jan Kara <jack@...e.cz>,
  krisman@...nel.org,  linux-mm@...ck.org,  linux-kernel@...r.kernel.org,
  linux-fsdevel@...r.kernel.org,  kernel-dev@...lia.com,  Daniel Rosenberg
 <drosen@...gle.com>,  smcv@...labora.com,  Christoph Hellwig <hch@....de>
Subject: Re: [PATCH v2 6/8] tmpfs: Add flag FS_CASEFOLD_FL support for tmpfs
 dirs

André Almeida <andrealmeid@...lia.com> writes:

> Enable setting flag FS_CASEFOLD_FL for tmpfs directories, when tmpfs is
> mounted with casefold support. A special check is need for this flag,
> since it can't be set for non-empty directories.
>
> Signed-off-by: André Almeida <andrealmeid@...lia.com>
> ---
>  include/linux/shmem_fs.h |  6 +++---
>  mm/shmem.c               | 40 +++++++++++++++++++++++++++++++++-------
>  2 files changed, 36 insertions(+), 10 deletions(-)
>
> diff --git a/include/linux/shmem_fs.h b/include/linux/shmem_fs.h
> index 1d06b1e5408a..8367ca2b99d9 100644
> --- a/include/linux/shmem_fs.h
> +++ b/include/linux/shmem_fs.h
> @@ -42,10 +42,10 @@ struct shmem_inode_info {
>  	struct inode		vfs_inode;
>  };
>  
> -#define SHMEM_FL_USER_VISIBLE		FS_FL_USER_VISIBLE
> +#define SHMEM_FL_USER_VISIBLE		(FS_FL_USER_VISIBLE | FS_CASEFOLD_FL)
>  #define SHMEM_FL_USER_MODIFIABLE \
> -	(FS_IMMUTABLE_FL | FS_APPEND_FL | FS_NODUMP_FL | FS_NOATIME_FL)
> -#define SHMEM_FL_INHERITED		(FS_NODUMP_FL | FS_NOATIME_FL)
> +	(FS_IMMUTABLE_FL | FS_APPEND_FL | FS_NODUMP_FL | FS_NOATIME_FL | FS_CASEFOLD_FL)
> +#define SHMEM_FL_INHERITED		(FS_NODUMP_FL | FS_NOATIME_FL | FS_CASEFOLD_FL)
>  
>  struct shmem_quota_limits {
>  	qsize_t usrquota_bhardlimit; /* Default user quota block hard limit */
> diff --git a/mm/shmem.c b/mm/shmem.c
> index 0f918010bc54..9a0fc7636629 100644
> --- a/mm/shmem.c
> +++ b/mm/shmem.c
> @@ -2617,9 +2617,26 @@ static int shmem_initxattrs(struct inode *, const struct xattr *, void *);
>   * chattr's fsflags are unrelated to extended attributes,
>   * but tmpfs has chosen to enable them under the same config option.
>   */
> -static void shmem_set_inode_flags(struct inode *inode, unsigned int fsflags)
> +static int shmem_set_inode_flags(struct inode *inode, unsigned int fsflags, struct dentry *dentry)
>  {
> -	unsigned int i_flags = 0;
> +	unsigned int i_flags = 0, old = inode->i_flags;
> +	struct super_block *sb = inode->i_sb;
> +
> +	if (fsflags & FS_CASEFOLD_FL) {
> +		if (!sb->s_encoding)
> +			return -EOPNOTSUPP;
> +
> +		if (!S_ISDIR(inode->i_mode))
> +			return -ENOTDIR;
> +
> +		if (dentry && !simple_empty(dentry))
> +			return -ENOTEMPTY;
> +
> +		i_flags |= S_CASEFOLD;
> +	} else if (old & S_CASEFOLD) {
> +		if (dentry && !simple_empty(dentry))
> +			return -ENOTEMPTY;

We don't want to fail if a directory already has the S_CASEFOLD
flag and we are not flipping it in the current operation.  Something like:

if ((fsflags ^ old) & S_CASEFOLD) {
	if (!sb->s_encoding)
		return -EOPNOTSUPP;

	if (!S_ISDIR(inode->i_mode))
		return -ENOTDIR;

	if (dentry && !simple_empty(dentry))
		return -ENOTEMPTY;
        i_flags |= fsflags & S_CASEFOLD;
}

>
>  	if (fsflags & FS_NOATIME_FL)
>  		i_flags |= S_NOATIME;
> @@ -2630,10 +2647,12 @@ static void shmem_set_inode_flags(struct inode *inode, unsigned int fsflags)
>  	/*
>  	 * But FS_NODUMP_FL does not require any action in i_flags.
>  	 */
> -	inode_set_flags(inode, i_flags, S_NOATIME | S_APPEND | S_IMMUTABLE);
> +	inode_set_flags(inode, i_flags, S_NOATIME | S_APPEND | S_IMMUTABLE | S_CASEFOLD);
> +
> +	return 0;
>  }
>  #else
> -static void shmem_set_inode_flags(struct inode *inode, unsigned int fsflags)
> +static void shmem_set_inode_flags(struct inode *inode, unsigned int fsflags, struct dentry *dentry)
>  {
>  }
>  #define shmem_initxattrs NULL
> @@ -2680,7 +2699,7 @@ static struct inode *__shmem_get_inode(struct mnt_idmap *idmap,
>  	info->fsflags = (dir == NULL) ? 0 :
>  		SHMEM_I(dir)->fsflags & SHMEM_FL_INHERITED;
>  	if (info->fsflags)
> -		shmem_set_inode_flags(inode, info->fsflags);
> +		shmem_set_inode_flags(inode, info->fsflags, NULL);
>  	INIT_LIST_HEAD(&info->shrinklist);
>  	INIT_LIST_HEAD(&info->swaplist);
>  	simple_xattrs_init(&info->xattrs);
> @@ -3790,16 +3809,23 @@ static int shmem_fileattr_set(struct mnt_idmap *idmap,
>  {
>  	struct inode *inode = d_inode(dentry);
>  	struct shmem_inode_info *info = SHMEM_I(inode);
> +	int ret, flags;
>  
>  	if (fileattr_has_fsx(fa))
>  		return -EOPNOTSUPP;
>  	if (fa->flags & ~SHMEM_FL_USER_MODIFIABLE)
>  		return -EOPNOTSUPP;
>  
> -	info->fsflags = (info->fsflags & ~SHMEM_FL_USER_MODIFIABLE) |
> +	flags = (info->fsflags & ~SHMEM_FL_USER_MODIFIABLE) |
>  		(fa->flags & SHMEM_FL_USER_MODIFIABLE);
>  
> -	shmem_set_inode_flags(inode, info->fsflags);
> +	ret = shmem_set_inode_flags(inode, flags, dentry);
> +
> +	if (ret)
> +		return ret;
> +
> +	info->fsflags = flags;
> +
>  	inode_set_ctime_current(inode);
>  	inode_inc_iversion(inode);
>  	return 0;

-- 
Gabriel Krisman Bertazi