Re: [PATCH v1 1/4] nfsd: Convert export flags to use BIT() macro

[Chuck Lever <cel@kernel.org>]

On 1/16/26 10:35 AM, Benjamin Coddington wrote:
> On 16 Jan 2026, at 10:31, Chuck Lever wrote:
> 
>> On Fri, Jan 16, 2026, at 9:32 AM, Benjamin Coddington wrote:
>>> Simplify these defines for consistency, readability, and clarity.
>>>
>>> Signed-off-by: Benjamin Coddington <bcodding@hammerspace.com>
>>> ---
>>>  fs/nfsd/nfsctl.c                 |  2 +-
>>>  include/uapi/linux/nfsd/export.h | 38 ++++++++++++++++----------------
>>>  2 files changed, 20 insertions(+), 20 deletions(-)
>>>
>>> diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c
>>> index 30caefb2522f..8ccc65bb09fd 100644
>>> --- a/fs/nfsd/nfsctl.c
>>> +++ b/fs/nfsd/nfsctl.c
>>> @@ -169,7 +169,7 @@ static const struct file_operations
>>> exports_nfsd_operations = {
>>>
>>>  static int export_features_show(struct seq_file *m, void *v)
>>>  {
>>> -	seq_printf(m, "0x%x 0x%x\n", NFSEXP_ALLFLAGS, NFSEXP_SECINFO_FLAGS);
>>> +	seq_printf(m, "0x%lx 0x%lx\n", NFSEXP_ALLFLAGS, NFSEXP_SECINFO_FLAGS);
>>>  	return 0;
>>>  }
>>>
>>> diff --git a/include/uapi/linux/nfsd/export.h
>>> b/include/uapi/linux/nfsd/export.h
>>> index a73ca3703abb..4e712bb02322 100644
>>> --- a/include/uapi/linux/nfsd/export.h
>>> +++ b/include/uapi/linux/nfsd/export.h
>>> @@ -26,22 +26,22 @@
>>>   * Please update the expflags[] array in fs/nfsd/export.c when adding
>>>   * a new flag.
>>>   */
>>> -#define NFSEXP_READONLY		0x0001
>>> -#define NFSEXP_INSECURE_PORT	0x0002
>>> -#define NFSEXP_ROOTSQUASH	0x0004
>>> -#define NFSEXP_ALLSQUASH	0x0008
>>> -#define NFSEXP_ASYNC		0x0010
>>> -#define NFSEXP_GATHERED_WRITES	0x0020
>>> -#define NFSEXP_NOREADDIRPLUS    0x0040
>>> -#define NFSEXP_SECURITY_LABEL	0x0080
>>> -/* 0x100 currently unused */
>>> -#define NFSEXP_NOHIDE		0x0200
>>> -#define NFSEXP_NOSUBTREECHECK	0x0400
>>> -#define	NFSEXP_NOAUTHNLM	0x0800		/* Don't authenticate NLM requests -
>>> just trust */
>>> -#define NFSEXP_MSNFS		0x1000	/* do silly things that MS clients
>>> expect; no longer supported */
>>> -#define NFSEXP_FSID		0x2000
>>> -#define	NFSEXP_CROSSMOUNT	0x4000
>>> -#define	NFSEXP_NOACL		0x8000	/* reserved for possible ACL related use
>>> */
>>> +#define NFSEXP_READONLY			BIT(0)
>>> +#define NFSEXP_INSECURE_PORT	BIT(1)
>>> +#define NFSEXP_ROOTSQUASH		BIT(2)
>>> +#define NFSEXP_ALLSQUASH		BIT(3)
>>> +#define NFSEXP_ASYNC			BIT(4)
>>> +#define NFSEXP_GATHERED_WRITES	BIT(5)
>>> +#define NFSEXP_NOREADDIRPLUS    BIT(6)
>>> +#define NFSEXP_SECURITY_LABEL	BIT(7)
>>> +/* BIT(8) currently unused */
>>> +#define NFSEXP_NOHIDE			BIT(9)
>>> +#define NFSEXP_NOSUBTREECHECK	BIT(10)
>>> +#define NFSEXP_NOAUTHNLM		BIT(11)	/* Don't authenticate NLM requests -
>>> just trust */
>>> +#define NFSEXP_MSNFS			BIT(12)	/* do silly things that MS clients
>>> expect; no longer supported */
>>> +#define NFSEXP_FSID				BIT(13)
>>> +#define NFSEXP_CROSSMOUNT		BIT(14)
>>> +#define NFSEXP_NOACL			BIT(15)	/* reserved for possible ACL related
>>> use */
>>>  /*
>>>   * The NFSEXP_V4ROOT flag causes the kernel to give access only to
>>> NFSv4
>>>   * clients, and only to the single directory that is the root of the
>>> @@ -51,11 +51,11 @@
>>>   * pseudofilesystem, which provides access only to paths leading to
>>> each
>>>   * exported filesystem.
>>>   */
>>> -#define	NFSEXP_V4ROOT		0x10000
>>> -#define NFSEXP_PNFS		0x20000
>>> +#define NFSEXP_V4ROOT			BIT(16)
>>> +#define NFSEXP_PNFS				BIT(17)
>>>
>>>  /* All flags that we claim to support.  (Note we don't support NOACL.) */
>>> -#define NFSEXP_ALLFLAGS		0x3FEFF
>>> +#define NFSEXP_ALLFLAGS			BIT(18) - BIT(8) - 1
>>>
>>>  /* The flags that may vary depending on security flavor: */
>>>  #define NFSEXP_SECINFO_FLAGS	(NFSEXP_READONLY | NFSEXP_ROOTSQUASH \
>>> -- 
>>> 2.50.1
>>
>> This might constitute a breaking user space API change. BIT() is
>> a kernel convention. What defines BIT() for user space consumers
>> of this header?
> 
> Doh - good catch.  I can drop this, or maybe add:
> 
> #ifndef BIT
> #define BIT(n) (1UL << (n))
> #endif
I'm happy leaving these as hex constants.


-- 
Chuck Lever