Message-Id: <38bf1452-8cf8-477b-bcc3-9fe442033bc5@app.fastmail.com>
Date: Tue, 20 Jan 2026 16:48:31 -0500
From: "Chuck Lever" <cel@...nel.org>
To: "Darrick J. Wong" <djwong@...nel.org>,
 "Christian Brauner" <brauner@...nel.org>
Cc: "Alexander Viro" <viro@...iv.linux.org.uk>, "Jan Kara" <jack@...e.cz>,
 linux-fsdevel@...r.kernel.org, linux-ext4@...r.kernel.org,
 linux-xfs@...r.kernel.org, linux-cifs@...r.kernel.org,
 linux-nfs@...r.kernel.org, linux-f2fs-devel@...ts.sourceforge.net,
 "OGAWA Hirofumi" <hirofumi@...l.parknet.co.jp>,
 "Namjae Jeon" <linkinjeon@...nel.org>,
 "Sungjong Seo" <sj1557.seo@...sung.com>,
 "Yuezhang Mo" <yuezhang.mo@...y.com>,
 almaz.alexandrovich@...agon-software.com,
 "Viacheslav Dubeyko" <slava@...eyko.com>, glaubitz@...sik.fu-berlin.de,
 frank.li@...o.com, "Theodore Tso" <tytso@....edu>,
 adilger.kernel@...ger.ca, "Carlos Maiolino" <cem@...nel.org>,
 "Steve French" <sfrench@...ba.org>, "Paulo Alcantara" <pc@...guebit.org>,
 "Ronnie Sahlberg" <ronniesahlberg@...il.com>,
 "Shyam Prasad N" <sprasad@...rosoft.com>,
 "Trond Myklebust" <trondmy@...nel.org>,
 "Anna Schumaker" <anna@...nel.org>, "Jaegeuk Kim" <jaegeuk@...nel.org>,
 "Chao Yu" <chao@...nel.org>, "Hans de Goede" <hansg@...nel.org>,
 senozhatsky@...omium.org, "Chuck Lever" <chuck.lever@...cle.com>
Subject: Re: [PATCH v6 01/16] fs: Add case sensitivity flags to file_kattr



On Tue, Jan 20, 2026, at 12:26 PM, Darrick J. Wong wrote:
> On Tue, Jan 20, 2026 at 09:24:24AM -0500, Chuck Lever wrote:
>> From: Chuck Lever <chuck.lever@...cle.com>
>> 
>> Enable upper layers such as NFSD to retrieve case sensitivity
>> information from file systems by adding FS_XFLAG_CASEFOLD and
>> FS_XFLAG_CASENONPRESERVING flags.
>> 
>> Filesystems report case-insensitive or case-nonpreserving behavior
>> by setting these flags directly in fa->fsx_xflags. The default
>> (flags unset) indicates POSIX semantics: case-sensitive and
>> case-preserving. These flags are read-only; userspace cannot set
>> them via ioctl.
>> 
>> Relocate struct file_kattr initialization from fileattr_fill_xflags()
>> and fileattr_fill_flags() to vfs_fileattr_get() and the ioctl/syscall
>> call sites. This allows filesystem ->fileattr_get() callbacks to set
>> flags directly in fa->fsx_xflags before invoking the fill functions,
>> which previously would have zeroed those values. Callers that bypass
>> vfs_fileattr_get() must now zero-initialize the struct themselves.
>> 
>> Case sensitivity information is exported to userspace via the
>> fa_xflags field in the FS_IOC_FSGETXATTR ioctl and file_getattr()
>> system call.
>> 
>> Signed-off-by: Chuck Lever <chuck.lever@...cle.com>
>> ---
>>  fs/file_attr.c           | 14 ++++++--------
>>  fs/xfs/xfs_ioctl.c       |  2 +-
>>  include/linux/fileattr.h |  3 ++-
>>  include/uapi/linux/fs.h  |  2 ++
>
> This ought to go to linux-api because you're changing the userspace api.
> Granted it's only adding a flag definition to an existing ioctl, but
> FS_XFLAG_CASEFOLD /does/ collide with Andrey's fsverity xflag patch...
>
> (The rest of the changes looks ok to me.)

Process question for Christian: Do you want to see a v7 of this
series with Cc: linux-api before proceeding, or are you taking
both Andrey's and mine and can resolve the conflict, or ... ?


> --D
>
>>  4 files changed, 11 insertions(+), 10 deletions(-)
>> 
>> diff --git a/fs/file_attr.c b/fs/file_attr.c
>> index 13cdb31a3e94..2700200c5b9c 100644
>> --- a/fs/file_attr.c
>> +++ b/fs/file_attr.c
>> @@ -15,12 +15,10 @@
>>   * @fa:		fileattr pointer
>>   * @xflags:	FS_XFLAG_* flags
>>   *
>> - * Set ->fsx_xflags, ->fsx_valid and ->flags (translated xflags).  All
>> - * other fields are zeroed.
>> + * Set ->fsx_xflags, ->fsx_valid and ->flags (translated xflags).
>>   */
>>  void fileattr_fill_xflags(struct file_kattr *fa, u32 xflags)
>>  {
>> -	memset(fa, 0, sizeof(*fa));
>>  	fa->fsx_valid = true;
>>  	fa->fsx_xflags = xflags;
>>  	if (fa->fsx_xflags & FS_XFLAG_IMMUTABLE)
>> @@ -46,11 +44,9 @@ EXPORT_SYMBOL(fileattr_fill_xflags);
>>   * @flags:	FS_*_FL flags
>>   *
>>   * Set ->flags, ->flags_valid and ->fsx_xflags (translated flags).
>> - * All other fields are zeroed.
>>   */
>>  void fileattr_fill_flags(struct file_kattr *fa, u32 flags)
>>  {
>> -	memset(fa, 0, sizeof(*fa));
>>  	fa->flags_valid = true;
>>  	fa->flags = flags;
>>  	if (fa->flags & FS_SYNC_FL)
>> @@ -84,6 +80,8 @@ int vfs_fileattr_get(struct dentry *dentry, struct file_kattr *fa)
>>  	struct inode *inode = d_inode(dentry);
>>  	int error;
>>  
>> +	memset(fa, 0, sizeof(*fa));
>> +
>>  	if (!inode->i_op->fileattr_get)
>>  		return -ENOIOCTLCMD;
>>  
>> @@ -323,7 +321,7 @@ int ioctl_setflags(struct file *file, unsigned int __user *argp)
>>  {
>>  	struct mnt_idmap *idmap = file_mnt_idmap(file);
>>  	struct dentry *dentry = file->f_path.dentry;
>> -	struct file_kattr fa;
>> +	struct file_kattr fa = {};
>>  	unsigned int flags;
>>  	int err;
>>  
>> @@ -355,7 +353,7 @@ int ioctl_fssetxattr(struct file *file, void __user *argp)
>>  {
>>  	struct mnt_idmap *idmap = file_mnt_idmap(file);
>>  	struct dentry *dentry = file->f_path.dentry;
>> -	struct file_kattr fa;
>> +	struct file_kattr fa = {};
>>  	int err;
>>  
>>  	err = copy_fsxattr_from_user(&fa, argp);
>> @@ -434,7 +432,7 @@ SYSCALL_DEFINE5(file_setattr, int, dfd, const char __user *, filename,
>>  	struct filename *name __free(putname) = NULL;
>>  	unsigned int lookup_flags = 0;
>>  	struct file_attr fattr;
>> -	struct file_kattr fa;
>> +	struct file_kattr fa = {};
>>  	int error;
>>  
>>  	BUILD_BUG_ON(sizeof(struct file_attr) < FILE_ATTR_SIZE_VER0);
>> diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c
>> index 59eaad774371..f0417c4d1fca 100644
>> --- a/fs/xfs/xfs_ioctl.c
>> +++ b/fs/xfs/xfs_ioctl.c
>> @@ -496,7 +496,7 @@ xfs_ioc_fsgetxattra(
>>  	xfs_inode_t		*ip,
>>  	void			__user *arg)
>>  {
>> -	struct file_kattr	fa;
>> +	struct file_kattr	fa = {};
>>  
>>  	xfs_ilock(ip, XFS_ILOCK_SHARED);
>>  	xfs_fill_fsxattr(ip, XFS_ATTR_FORK, &fa);
>> diff --git a/include/linux/fileattr.h b/include/linux/fileattr.h
>> index f89dcfad3f8f..709de829659f 100644
>> --- a/include/linux/fileattr.h
>> +++ b/include/linux/fileattr.h
>> @@ -16,7 +16,8 @@
>>  
>>  /* Read-only inode flags */
>>  #define FS_XFLAG_RDONLY_MASK \
>> -	(FS_XFLAG_PREALLOC | FS_XFLAG_HASATTR)
>> +	(FS_XFLAG_PREALLOC | FS_XFLAG_HASATTR | \
>> +	 FS_XFLAG_CASEFOLD | FS_XFLAG_CASENONPRESERVING)
>>  
>>  /* Flags to indicate valid value of fsx_ fields */
>>  #define FS_XFLAG_VALUES_MASK \
>> diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h
>> index 66ca526cf786..919148beaa8c 100644
>> --- a/include/uapi/linux/fs.h
>> +++ b/include/uapi/linux/fs.h
>> @@ -253,6 +253,8 @@ struct file_attr {
>>  #define FS_XFLAG_FILESTREAM	0x00004000	/* use filestream allocator */
>>  #define FS_XFLAG_DAX		0x00008000	/* use DAX for IO */
>>  #define FS_XFLAG_COWEXTSIZE	0x00010000	/* CoW extent size allocator hint */
>> +#define FS_XFLAG_CASEFOLD	0x00020000	/* case-insensitive lookups */
>> +#define FS_XFLAG_CASENONPRESERVING 0x00040000	/* case not preserved */
>>  #define FS_XFLAG_HASATTR	0x80000000	/* no DIFLAG for this	*/
>>  
>>  /* the read-only stuff doesn't really belong here, but any other place is
>> -- 
>> 2.52.0
>> 
>>

-- 
Chuck Lever

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