linux-kernel - Re: [PATCH v4 08/10] tmpfs: Add flag FS_CASEFOLD

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Message-ID: <87wmjgk7ru.fsf@mailhost.krisman.be>
Date: Thu, 12 Sep 2024 15:10:29 -0400
From: Gabriel Krisman Bertazi <gabriel@...sman.be>
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>,
  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>,
  Theodore Ts'o <tytso@....edu>
Subject: Re: [PATCH v4 08/10] 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.

Reviewed-by: Gabriel Krisman Bertazi <krisman@...e.de>

>
> Signed-off-by: André Almeida <andrealmeid@...lia.com>
> ---
> Changes from v2:
> - Fixed bug when adding a non-casefold flag in a non-empty dir
> ---
>  include/linux/shmem_fs.h |  6 ++--
>  mm/shmem.c               | 70 ++++++++++++++++++++++++++++++++++++----
>  2 files changed, 67 insertions(+), 9 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 4fde63596ab3..fc0e0cd46146 100644
> --- a/mm/shmem.c
> +++ b/mm/shmem.c
> @@ -2613,13 +2613,62 @@ static int shmem_file_open(struct inode *inode, struct file *file)
>  #ifdef CONFIG_TMPFS_XATTR
>  static int shmem_initxattrs(struct inode *, const struct xattr *, void *);
>  
> +#if IS_ENABLED(CONFIG_UNICODE)
> +/*
> + * shmem_inode_casefold_flags - Deal with casefold file attribute flag
> + *
> + * The casefold file attribute needs some special checks. I can just be added to
> + * an empty dir, and can't be removed from a non-empty dir.
> + */
> +static int shmem_inode_casefold_flags(struct inode *inode, unsigned int fsflags,
> +				      struct dentry *dentry, unsigned int *i_flags)
> +{
> +	unsigned int old = inode->i_flags;
> +	struct super_block *sb = inode->i_sb;
> +
> +	if (fsflags & FS_CASEFOLD_FL) {
> +		if (!(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 = *i_flags | S_CASEFOLD;
> +	} else if (old & S_CASEFOLD) {
> +		if (dentry && !simple_empty(dentry))
> +			return -ENOTEMPTY;
> +	}
> +
> +	return 0;
> +}
> +#else
> +static int shmem_inode_casefold_flags(struct inode *inode, unsigned int fsflags,
> +				      struct dentry *dentry, unsigned int *i_flags)
> +{
> +	if (fsflags & FS_CASEFOLD_FL)
> +		return -EOPNOTSUPP;
> +
> +	return 0;
> +}
> +#endif
> +
>  /*
>   * 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;
> +	int ret;
> +
> +	ret = shmem_inode_casefold_flags(inode, fsflags, dentry, &i_flags);
> +	if (ret)
> +		return ret;
>  
>  	if (fsflags & FS_NOATIME_FL)
>  		i_flags |= S_NOATIME;
> @@ -2630,10 +2679,12 @@ 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 +2731,7 @@ 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);
> @@ -3789,16 +3840,23 @@ 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