[PATCH 1/5] nfsd: only call inode_query_iversion in the I_VERSION case

[PATCH 1/5] nfsd: only call inode_query_iversion in the I_VERSION case

[J. Bruce Fields]

From: "J. Bruce Fields" <bfields@redhat.com>

inode_query_iversion() can modify i_version.  Depending on the exported
filesystem, that may not be safe.  For example, if you're re-exporting
NFS, NFS stores the server's change attribute in i_version and does not
expect it to be modified locally.  This has been observed causing
unnecessary cache invalidations.

The way a filesystem indicates that it's OK to call
inode_query_iverson() is by setting SB_I_VERSION.

So, move the I_VERSION check out of encode_change(), where it's used
only in FATTR responses, to nfsd4_changeattr(), which is also called for
pre- and post- operation attributes.

(Note we could also pull the NFSEXP_V4ROOT case into
nfsd4_change_attribute as well.  That would actually be a no-op, since
pre/post attrs are only used for metadata-modifying operations, and
V4ROOT exports are read-only.  But we might make the change in the
future just for simplicity.)

Reported-by: Daire Byrne <daire@dneg.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
---
 fs/nfsd/nfs3xdr.c |  5 ++---
 fs/nfsd/nfs4xdr.c |  6 +-----
 fs/nfsd/nfsfh.h   | 14 ++++++++++----
 3 files changed, 13 insertions(+), 12 deletions(-)

diff --git a/fs/nfsd/nfs3xdr.c b/fs/nfsd/nfs3xdr.c
index 2277f83da250..dfbf390ff40c 100644
--- a/fs/nfsd/nfs3xdr.c
+++ b/fs/nfsd/nfs3xdr.c
@@ -291,14 +291,13 @@ void fill_post_wcc(struct svc_fh *fhp)
 		printk("nfsd: inode locked twice during operation.\n");
 
 	err = fh_getattr(fhp, &fhp->fh_post_attr);
-	fhp->fh_post_change = nfsd4_change_attribute(&fhp->fh_post_attr,
-						     d_inode(fhp->fh_dentry));
 	if (err) {
 		fhp->fh_post_saved = false;
-		/* Grab the ctime anyway - set_change_info might use it */
 		fhp->fh_post_attr.ctime = d_inode(fhp->fh_dentry)->i_ctime;
 	} else
 		fhp->fh_post_saved = true;
+	fhp->fh_post_change = nfsd4_change_attribute(&fhp->fh_post_attr,
+						     d_inode(fhp->fh_dentry));
 }
 
 /*
diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
index 833a2c64dfe8..56fd5f6d5c44 100644
--- a/fs/nfsd/nfs4xdr.c
+++ b/fs/nfsd/nfs4xdr.c
@@ -2298,12 +2298,8 @@ static __be32 *encode_change(__be32 *p, struct kstat *stat, struct inode *inode,
 	if (exp->ex_flags & NFSEXP_V4ROOT) {
 		*p++ = cpu_to_be32(convert_to_wallclock(exp->cd->flush_time));
 		*p++ = 0;
-	} else if (IS_I_VERSION(inode)) {
+	} else
 		p = xdr_encode_hyper(p, nfsd4_change_attribute(stat, inode));
-	} else {
-		*p++ = cpu_to_be32(stat->ctime.tv_sec);
-		*p++ = cpu_to_be32(stat->ctime.tv_nsec);
-	}
 	return p;
 }
 
diff --git a/fs/nfsd/nfsfh.h b/fs/nfsd/nfsfh.h
index 56cfbc361561..3faf5974fa4e 100644
--- a/fs/nfsd/nfsfh.h
+++ b/fs/nfsd/nfsfh.h
@@ -261,10 +261,16 @@ static inline u64 nfsd4_change_attribute(struct kstat *stat,
 {
 	u64 chattr;
 
-	chattr =  stat->ctime.tv_sec;
-	chattr <<= 30;
-	chattr += stat->ctime.tv_nsec;
-	chattr += inode_query_iversion(inode);
+	if (IS_I_VERSION(inode)) {
+		chattr =  stat->ctime.tv_sec;
+		chattr <<= 30;
+		chattr += stat->ctime.tv_nsec;
+		chattr += inode_query_iversion(inode);
+	} else {
+		chattr = cpu_to_be32(stat->ctime.tv_sec);
+		chattr <<= 32;
+		chattr += cpu_to_be32(stat->ctime.tv_nsec);
+	}
 	return chattr;
 }
 
-- 
2.28.0

Re: [PATCH 1/5] nfsd: only call inode_query_iversion in the I_VERSION case

[J. Bruce Fields]

This patch fixes the bug Daire saw.  The rest is a replacement for the
series I sent before, except that I haven't included the last few
patches, which will need review from other filesystem people.

--b.

On Mon, Nov 30, 2020 at 02:38:53PM -0500, J. Bruce Fields wrote:
> From: "J. Bruce Fields" <bfields@redhat.com>
> 
> inode_query_iversion() can modify i_version.  Depending on the exported
> filesystem, that may not be safe.  For example, if you're re-exporting
> NFS, NFS stores the server's change attribute in i_version and does not
> expect it to be modified locally.  This has been observed causing
> unnecessary cache invalidations.
> 
> The way a filesystem indicates that it's OK to call
> inode_query_iverson() is by setting SB_I_VERSION.
> 
> So, move the I_VERSION check out of encode_change(), where it's used
> only in FATTR responses, to nfsd4_changeattr(), which is also called for
> pre- and post- operation attributes.
> 
> (Note we could also pull the NFSEXP_V4ROOT case into
> nfsd4_change_attribute as well.  That would actually be a no-op, since
> pre/post attrs are only used for metadata-modifying operations, and
> V4ROOT exports are read-only.  But we might make the change in the
> future just for simplicity.)
> 
> Reported-by: Daire Byrne <daire@dneg.com>
> Signed-off-by: J. Bruce Fields <bfields@redhat.com>
> ---
>  fs/nfsd/nfs3xdr.c |  5 ++---
>  fs/nfsd/nfs4xdr.c |  6 +-----
>  fs/nfsd/nfsfh.h   | 14 ++++++++++----
>  3 files changed, 13 insertions(+), 12 deletions(-)
> 
> diff --git a/fs/nfsd/nfs3xdr.c b/fs/nfsd/nfs3xdr.c
> index 2277f83da250..dfbf390ff40c 100644
> --- a/fs/nfsd/nfs3xdr.c
> +++ b/fs/nfsd/nfs3xdr.c
> @@ -291,14 +291,13 @@ void fill_post_wcc(struct svc_fh *fhp)
>  		printk("nfsd: inode locked twice during operation.\n");
>  
>  	err = fh_getattr(fhp, &fhp->fh_post_attr);
> -	fhp->fh_post_change = nfsd4_change_attribute(&fhp->fh_post_attr,
> -						     d_inode(fhp->fh_dentry));
>  	if (err) {
>  		fhp->fh_post_saved = false;
> -		/* Grab the ctime anyway - set_change_info might use it */
>  		fhp->fh_post_attr.ctime = d_inode(fhp->fh_dentry)->i_ctime;
>  	} else
>  		fhp->fh_post_saved = true;
> +	fhp->fh_post_change = nfsd4_change_attribute(&fhp->fh_post_attr,
> +						     d_inode(fhp->fh_dentry));
>  }
>  
>  /*
> diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
> index 833a2c64dfe8..56fd5f6d5c44 100644
> --- a/fs/nfsd/nfs4xdr.c
> +++ b/fs/nfsd/nfs4xdr.c
> @@ -2298,12 +2298,8 @@ static __be32 *encode_change(__be32 *p, struct kstat *stat, struct inode *inode,
>  	if (exp->ex_flags & NFSEXP_V4ROOT) {
>  		*p++ = cpu_to_be32(convert_to_wallclock(exp->cd->flush_time));
>  		*p++ = 0;
> -	} else if (IS_I_VERSION(inode)) {
> +	} else
>  		p = xdr_encode_hyper(p, nfsd4_change_attribute(stat, inode));
> -	} else {
> -		*p++ = cpu_to_be32(stat->ctime.tv_sec);
> -		*p++ = cpu_to_be32(stat->ctime.tv_nsec);
> -	}
>  	return p;
>  }
>  
> diff --git a/fs/nfsd/nfsfh.h b/fs/nfsd/nfsfh.h
> index 56cfbc361561..3faf5974fa4e 100644
> --- a/fs/nfsd/nfsfh.h
> +++ b/fs/nfsd/nfsfh.h
> @@ -261,10 +261,16 @@ static inline u64 nfsd4_change_attribute(struct kstat *stat,
>  {
>  	u64 chattr;
>  
> -	chattr =  stat->ctime.tv_sec;
> -	chattr <<= 30;
> -	chattr += stat->ctime.tv_nsec;
> -	chattr += inode_query_iversion(inode);
> +	if (IS_I_VERSION(inode)) {
> +		chattr =  stat->ctime.tv_sec;
> +		chattr <<= 30;
> +		chattr += stat->ctime.tv_nsec;
> +		chattr += inode_query_iversion(inode);
> +	} else {
> +		chattr = cpu_to_be32(stat->ctime.tv_sec);
> +		chattr <<= 32;
> +		chattr += cpu_to_be32(stat->ctime.tv_nsec);
> +	}
>  	return chattr;
>  }
>  
> -- 
> 2.28.0

Re: [PATCH 1/5] nfsd: only call inode_query_iversion in the I_VERSION case

[Chuck Lever]

> On Nov 30, 2020, at 2:38 PM, J. Bruce Fields <bfields@fieldses.org> wrote:
> 
> From: "J. Bruce Fields" <bfields@redhat.com>
> 
> inode_query_iversion() can modify i_version.  Depending on the exported
> filesystem, that may not be safe.  For example, if you're re-exporting
> NFS, NFS stores the server's change attribute in i_version and does not
> expect it to be modified locally.  This has been observed causing
> unnecessary cache invalidations.
> 
> The way a filesystem indicates that it's OK to call
> inode_query_iverson() is by setting SB_I_VERSION.
> 
> So, move the I_VERSION check out of encode_change(), where it's used
> only in FATTR responses, to nfsd4_changeattr(), which is also called for
> pre- and post- operation attributes.
> 
> (Note we could also pull the NFSEXP_V4ROOT case into
> nfsd4_change_attribute as well.  That would actually be a no-op, since
> pre/post attrs are only used for metadata-modifying operations, and
> V4ROOT exports are read-only.  But we might make the change in the
> future just for simplicity.)
> 
> Reported-by: Daire Byrne <daire@dneg.com>
> Signed-off-by: J. Bruce Fields <bfields@redhat.com>

New sparse warnings after this one is applied:

/home/cel/src/linux/linux/fs/nfsd/nfsfh.h:270:24: warning: incorrect type in assignment (different base types)
/home/cel/src/linux/linux/fs/nfsd/nfsfh.h:270:24:    expected unsigned long long [assigned] [usertype] chattr
/home/cel/src/linux/linux/fs/nfsd/nfsfh.h:270:24:    got restricted __be32 [usertype]
/home/cel/src/linux/linux/fs/nfsd/nfsfh.h:272:24: warning: invalid assignment: +=
/home/cel/src/linux/linux/fs/nfsd/nfsfh.h:272:24:    left side has type unsigned long long
/home/cel/src/linux/linux/fs/nfsd/nfsfh.h:272:24:    right side has type restricted __be32
/home/cel/src/linux/linux/fs/nfsd/nfsfh.h:270:24: warning: incorrect type in assignment (different base types)
/home/cel/src/linux/linux/fs/nfsd/nfsfh.h:270:24:    expected unsigned long long [assigned] [usertype] chattr
/home/cel/src/linux/linux/fs/nfsd/nfsfh.h:270:24:    got restricted __be32 [usertype]
/home/cel/src/linux/linux/fs/nfsd/nfsfh.h:272:24: warning: invalid assignment: +=
/home/cel/src/linux/linux/fs/nfsd/nfsfh.h:272:24:    left side has type unsigned long long
/home/cel/src/linux/linux/fs/nfsd/nfsfh.h:272:24:    right side has type restricted __be32


> ---
> fs/nfsd/nfs3xdr.c |  5 ++---
> fs/nfsd/nfs4xdr.c |  6 +-----
> fs/nfsd/nfsfh.h   | 14 ++++++++++----
> 3 files changed, 13 insertions(+), 12 deletions(-)
> 
> diff --git a/fs/nfsd/nfs3xdr.c b/fs/nfsd/nfs3xdr.c
> index 2277f83da250..dfbf390ff40c 100644
> --- a/fs/nfsd/nfs3xdr.c
> +++ b/fs/nfsd/nfs3xdr.c
> @@ -291,14 +291,13 @@ void fill_post_wcc(struct svc_fh *fhp)
> 		printk("nfsd: inode locked twice during operation.\n");
> 
> 	err = fh_getattr(fhp, &fhp->fh_post_attr);
> -	fhp->fh_post_change = nfsd4_change_attribute(&fhp->fh_post_attr,
> -						     d_inode(fhp->fh_dentry));
> 	if (err) {
> 		fhp->fh_post_saved = false;
> -		/* Grab the ctime anyway - set_change_info might use it */
> 		fhp->fh_post_attr.ctime = d_inode(fhp->fh_dentry)->i_ctime;
> 	} else
> 		fhp->fh_post_saved = true;
> +	fhp->fh_post_change = nfsd4_change_attribute(&fhp->fh_post_attr,
> +						     d_inode(fhp->fh_dentry));
> }
> 
> /*
> diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
> index 833a2c64dfe8..56fd5f6d5c44 100644
> --- a/fs/nfsd/nfs4xdr.c
> +++ b/fs/nfsd/nfs4xdr.c
> @@ -2298,12 +2298,8 @@ static __be32 *encode_change(__be32 *p, struct kstat *stat, struct inode *inode,
> 	if (exp->ex_flags & NFSEXP_V4ROOT) {
> 		*p++ = cpu_to_be32(convert_to_wallclock(exp->cd->flush_time));
> 		*p++ = 0;
> -	} else if (IS_I_VERSION(inode)) {
> +	} else
> 		p = xdr_encode_hyper(p, nfsd4_change_attribute(stat, inode));
> -	} else {
> -		*p++ = cpu_to_be32(stat->ctime.tv_sec);
> -		*p++ = cpu_to_be32(stat->ctime.tv_nsec);
> -	}
> 	return p;
> }
> 
> diff --git a/fs/nfsd/nfsfh.h b/fs/nfsd/nfsfh.h
> index 56cfbc361561..3faf5974fa4e 100644
> --- a/fs/nfsd/nfsfh.h
> +++ b/fs/nfsd/nfsfh.h
> @@ -261,10 +261,16 @@ static inline u64 nfsd4_change_attribute(struct kstat *stat,
> {
> 	u64 chattr;
> 
> -	chattr =  stat->ctime.tv_sec;
> -	chattr <<= 30;
> -	chattr += stat->ctime.tv_nsec;
> -	chattr += inode_query_iversion(inode);
> +	if (IS_I_VERSION(inode)) {
> +		chattr =  stat->ctime.tv_sec;
> +		chattr <<= 30;
> +		chattr += stat->ctime.tv_nsec;
> +		chattr += inode_query_iversion(inode);
> +	} else {
> +		chattr = cpu_to_be32(stat->ctime.tv_sec);
> +		chattr <<= 32;
> +		chattr += cpu_to_be32(stat->ctime.tv_nsec);
> +	}
> 	return chattr;
> }
> 
> -- 
> 2.28.0
> 

--
Chuck Lever

Re: [PATCH 1/5] nfsd: only call inode_query_iversion in the I_VERSION case

[Bruce Fields]

On Mon, Nov 30, 2020 at 04:03:23PM -0500, Chuck Lever wrote:
> 
> 
> > On Nov 30, 2020, at 2:38 PM, J. Bruce Fields <bfields@fieldses.org> wrote:
> > 
> > From: "J. Bruce Fields" <bfields@redhat.com>
> > 
> > inode_query_iversion() can modify i_version.  Depending on the exported
> > filesystem, that may not be safe.  For example, if you're re-exporting
> > NFS, NFS stores the server's change attribute in i_version and does not
> > expect it to be modified locally.  This has been observed causing
> > unnecessary cache invalidations.
> > 
> > The way a filesystem indicates that it's OK to call
> > inode_query_iverson() is by setting SB_I_VERSION.
> > 
> > So, move the I_VERSION check out of encode_change(), where it's used
> > only in FATTR responses, to nfsd4_changeattr(), which is also called for
> > pre- and post- operation attributes.
> > 
> > (Note we could also pull the NFSEXP_V4ROOT case into
> > nfsd4_change_attribute as well.  That would actually be a no-op, since
> > pre/post attrs are only used for metadata-modifying operations, and
> > V4ROOT exports are read-only.  But we might make the change in the
> > future just for simplicity.)
> > 
> > Reported-by: Daire Byrne <daire@dneg.com>
> > Signed-off-by: J. Bruce Fields <bfields@redhat.com>
> 
> New sparse warnings after this one is applied:

D'oh.  I'll send again, thanks!

--b.

> 
> /home/cel/src/linux/linux/fs/nfsd/nfsfh.h:270:24: warning: incorrect type in assignment (different base types)
> /home/cel/src/linux/linux/fs/nfsd/nfsfh.h:270:24:    expected unsigned long long [assigned] [usertype] chattr
> /home/cel/src/linux/linux/fs/nfsd/nfsfh.h:270:24:    got restricted __be32 [usertype]
> /home/cel/src/linux/linux/fs/nfsd/nfsfh.h:272:24: warning: invalid assignment: +=
> /home/cel/src/linux/linux/fs/nfsd/nfsfh.h:272:24:    left side has type unsigned long long
> /home/cel/src/linux/linux/fs/nfsd/nfsfh.h:272:24:    right side has type restricted __be32
> /home/cel/src/linux/linux/fs/nfsd/nfsfh.h:270:24: warning: incorrect type in assignment (different base types)
> /home/cel/src/linux/linux/fs/nfsd/nfsfh.h:270:24:    expected unsigned long long [assigned] [usertype] chattr
> /home/cel/src/linux/linux/fs/nfsd/nfsfh.h:270:24:    got restricted __be32 [usertype]
> /home/cel/src/linux/linux/fs/nfsd/nfsfh.h:272:24: warning: invalid assignment: +=
> /home/cel/src/linux/linux/fs/nfsd/nfsfh.h:272:24:    left side has type unsigned long long
> /home/cel/src/linux/linux/fs/nfsd/nfsfh.h:272:24:    right side has type restricted __be32
> 
> 
> > ---
> > fs/nfsd/nfs3xdr.c |  5 ++---
> > fs/nfsd/nfs4xdr.c |  6 +-----
> > fs/nfsd/nfsfh.h   | 14 ++++++++++----
> > 3 files changed, 13 insertions(+), 12 deletions(-)
> > 
> > diff --git a/fs/nfsd/nfs3xdr.c b/fs/nfsd/nfs3xdr.c
> > index 2277f83da250..dfbf390ff40c 100644
> > --- a/fs/nfsd/nfs3xdr.c
> > +++ b/fs/nfsd/nfs3xdr.c
> > @@ -291,14 +291,13 @@ void fill_post_wcc(struct svc_fh *fhp)
> > 		printk("nfsd: inode locked twice during operation.\n");
> > 
> > 	err = fh_getattr(fhp, &fhp->fh_post_attr);
> > -	fhp->fh_post_change = nfsd4_change_attribute(&fhp->fh_post_attr,
> > -						     d_inode(fhp->fh_dentry));
> > 	if (err) {
> > 		fhp->fh_post_saved = false;
> > -		/* Grab the ctime anyway - set_change_info might use it */
> > 		fhp->fh_post_attr.ctime = d_inode(fhp->fh_dentry)->i_ctime;
> > 	} else
> > 		fhp->fh_post_saved = true;
> > +	fhp->fh_post_change = nfsd4_change_attribute(&fhp->fh_post_attr,
> > +						     d_inode(fhp->fh_dentry));
> > }
> > 
> > /*
> > diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
> > index 833a2c64dfe8..56fd5f6d5c44 100644
> > --- a/fs/nfsd/nfs4xdr.c
> > +++ b/fs/nfsd/nfs4xdr.c
> > @@ -2298,12 +2298,8 @@ static __be32 *encode_change(__be32 *p, struct kstat *stat, struct inode *inode,
> > 	if (exp->ex_flags & NFSEXP_V4ROOT) {
> > 		*p++ = cpu_to_be32(convert_to_wallclock(exp->cd->flush_time));
> > 		*p++ = 0;
> > -	} else if (IS_I_VERSION(inode)) {
> > +	} else
> > 		p = xdr_encode_hyper(p, nfsd4_change_attribute(stat, inode));
> > -	} else {
> > -		*p++ = cpu_to_be32(stat->ctime.tv_sec);
> > -		*p++ = cpu_to_be32(stat->ctime.tv_nsec);
> > -	}
> > 	return p;
> > }
> > 
> > diff --git a/fs/nfsd/nfsfh.h b/fs/nfsd/nfsfh.h
> > index 56cfbc361561..3faf5974fa4e 100644
> > --- a/fs/nfsd/nfsfh.h
> > +++ b/fs/nfsd/nfsfh.h
> > @@ -261,10 +261,16 @@ static inline u64 nfsd4_change_attribute(struct kstat *stat,
> > {
> > 	u64 chattr;
> > 
> > -	chattr =  stat->ctime.tv_sec;
> > -	chattr <<= 30;
> > -	chattr += stat->ctime.tv_nsec;
> > -	chattr += inode_query_iversion(inode);
> > +	if (IS_I_VERSION(inode)) {
> > +		chattr =  stat->ctime.tv_sec;
> > +		chattr <<= 30;
> > +		chattr += stat->ctime.tv_nsec;
> > +		chattr += inode_query_iversion(inode);
> > +	} else {
> > +		chattr = cpu_to_be32(stat->ctime.tv_sec);
> > +		chattr <<= 32;
> > +		chattr += cpu_to_be32(stat->ctime.tv_nsec);
> > +	}
> > 	return chattr;
> > }
> > 
> > -- 
> > 2.28.0
> > 
> 
> --
> Chuck Lever
> 
> 

[PATCH 1/5] nfsd: only call inode_query_iversion in the I_VERSION case

[J. Bruce Fields]

From: "J. Bruce Fields" <bfields@redhat.com>

inode_query_iversion() can modify i_version.  Depending on the exported
filesystem, that may not be safe.  For example, if you're re-exporting
NFS, NFS stores the server's change attribute in i_version and does not
expect it to be modified locally.  This has been observed causing
unnecessary cache invalidations.

The way a filesystem indicates that it's OK to call
inode_query_iverson() is by setting SB_I_VERSION.

So, move the I_VERSION check out of encode_change(), where it's used
only in FATTR responses, to nfsd4_changeattr(), which is also called for
pre- and post- operation attributes.

(Note we could also pull the NFSEXP_V4ROOT case into
nfsd4_change_attribute as well.  That would actually be a no-op, since
pre/post attrs are only used for metadata-modifying operations, and
V4ROOT exports are read-only.  But we might make the change in the
future just for simplicity.)

Reported-by: Daire Byrne <daire@dneg.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
---
 fs/nfsd/nfs3xdr.c |  5 ++---
 fs/nfsd/nfs4xdr.c |  6 +-----
 fs/nfsd/nfsfh.h   | 14 ++++++++++----
 3 files changed, 13 insertions(+), 12 deletions(-)

diff --git a/fs/nfsd/nfs3xdr.c b/fs/nfsd/nfs3xdr.c
index 2277f83da250..dfbf390ff40c 100644
--- a/fs/nfsd/nfs3xdr.c
+++ b/fs/nfsd/nfs3xdr.c
@@ -291,14 +291,13 @@ void fill_post_wcc(struct svc_fh *fhp)
 		printk("nfsd: inode locked twice during operation.\n");
 
 	err = fh_getattr(fhp, &fhp->fh_post_attr);
-	fhp->fh_post_change = nfsd4_change_attribute(&fhp->fh_post_attr,
-						     d_inode(fhp->fh_dentry));
 	if (err) {
 		fhp->fh_post_saved = false;
-		/* Grab the ctime anyway - set_change_info might use it */
 		fhp->fh_post_attr.ctime = d_inode(fhp->fh_dentry)->i_ctime;
 	} else
 		fhp->fh_post_saved = true;
+	fhp->fh_post_change = nfsd4_change_attribute(&fhp->fh_post_attr,
+						     d_inode(fhp->fh_dentry));
 }
 
 /*
diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
index 833a2c64dfe8..56fd5f6d5c44 100644
--- a/fs/nfsd/nfs4xdr.c
+++ b/fs/nfsd/nfs4xdr.c
@@ -2298,12 +2298,8 @@ static __be32 *encode_change(__be32 *p, struct kstat *stat, struct inode *inode,
 	if (exp->ex_flags & NFSEXP_V4ROOT) {
 		*p++ = cpu_to_be32(convert_to_wallclock(exp->cd->flush_time));
 		*p++ = 0;
-	} else if (IS_I_VERSION(inode)) {
+	} else
 		p = xdr_encode_hyper(p, nfsd4_change_attribute(stat, inode));
-	} else {
-		*p++ = cpu_to_be32(stat->ctime.tv_sec);
-		*p++ = cpu_to_be32(stat->ctime.tv_nsec);
-	}
 	return p;
 }
 
diff --git a/fs/nfsd/nfsfh.h b/fs/nfsd/nfsfh.h
index 56cfbc361561..39d764b129fa 100644
--- a/fs/nfsd/nfsfh.h
+++ b/fs/nfsd/nfsfh.h
@@ -261,10 +261,16 @@ static inline u64 nfsd4_change_attribute(struct kstat *stat,
 {
 	u64 chattr;
 
-	chattr =  stat->ctime.tv_sec;
-	chattr <<= 30;
-	chattr += stat->ctime.tv_nsec;
-	chattr += inode_query_iversion(inode);
+	if (IS_I_VERSION(inode)) {
+		chattr =  stat->ctime.tv_sec;
+		chattr <<= 30;
+		chattr += stat->ctime.tv_nsec;
+		chattr += inode_query_iversion(inode);
+	} else {
+		chattr = stat->ctime.tv_sec;
+		chattr <<= 32;
+		chattr += stat->ctime.tv_nsec;
+	}
 	return chattr;
 }
 
-- 
2.28.0

[PATCH 2/5] nfsd: simplify nfsd4_change_info

[J. Bruce Fields]

From: "J. Bruce Fields" <bfields@redhat.com>

It doesn't make sense to carry all these extra fields around.  Just
make everything into change attribute from the start.

This is just cleanup, there should be no change in behavior.

Signed-off-by: J. Bruce Fields <bfields@redhat.com>
---
 fs/nfsd/nfs4xdr.c | 11 ++---------
 fs/nfsd/xdr4.h    | 11 -----------
 2 files changed, 2 insertions(+), 20 deletions(-)

diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
index 56fd5f6d5c44..18c912930947 100644
--- a/fs/nfsd/nfs4xdr.c
+++ b/fs/nfsd/nfs4xdr.c
@@ -2331,15 +2331,8 @@ static __be32 *encode_time_delta(__be32 *p, struct inode *inode)
 static __be32 *encode_cinfo(__be32 *p, struct nfsd4_change_info *c)
 {
 	*p++ = cpu_to_be32(c->atomic);
-	if (c->change_supported) {
-		p = xdr_encode_hyper(p, c->before_change);
-		p = xdr_encode_hyper(p, c->after_change);
-	} else {
-		*p++ = cpu_to_be32(c->before_ctime_sec);
-		*p++ = cpu_to_be32(c->before_ctime_nsec);
-		*p++ = cpu_to_be32(c->after_ctime_sec);
-		*p++ = cpu_to_be32(c->after_ctime_nsec);
-	}
+	p = xdr_encode_hyper(p, c->before_change);
+	p = xdr_encode_hyper(p, c->after_change);
 	return p;
 }
 
diff --git a/fs/nfsd/xdr4.h b/fs/nfsd/xdr4.h
index 679d40af1bbb..3a59053084e6 100644
--- a/fs/nfsd/xdr4.h
+++ b/fs/nfsd/xdr4.h
@@ -76,12 +76,7 @@ static inline bool nfsd4_has_session(struct nfsd4_compound_state *cs)
 
 struct nfsd4_change_info {
 	u32		atomic;
-	bool		change_supported;
-	u32		before_ctime_sec;
-	u32		before_ctime_nsec;
 	u64		before_change;
-	u32		after_ctime_sec;
-	u32		after_ctime_nsec;
 	u64		after_change;
 };
 
@@ -768,15 +763,9 @@ set_change_info(struct nfsd4_change_info *cinfo, struct svc_fh *fhp)
 {
 	BUG_ON(!fhp->fh_pre_saved);
 	cinfo->atomic = (u32)fhp->fh_post_saved;
-	cinfo->change_supported = IS_I_VERSION(d_inode(fhp->fh_dentry));
 
 	cinfo->before_change = fhp->fh_pre_change;
 	cinfo->after_change = fhp->fh_post_change;
-	cinfo->before_ctime_sec = fhp->fh_pre_ctime.tv_sec;
-	cinfo->before_ctime_nsec = fhp->fh_pre_ctime.tv_nsec;
-	cinfo->after_ctime_sec = fhp->fh_post_attr.ctime.tv_sec;
-	cinfo->after_ctime_nsec = fhp->fh_post_attr.ctime.tv_nsec;
-
 }
 
 
-- 
2.28.0

[PATCH 3/5] nfsd: minor nfsd4_change_attribute cleanup

[J. Bruce Fields]

From: "J. Bruce Fields" <bfields@redhat.com>

Minor cleanup, no change in behavior.

Also pull out a common helper that'll be useful elsewhere.

Signed-off-by: J. Bruce Fields <bfields@redhat.com>
---
 fs/nfsd/nfsfh.h          | 13 +++++--------
 include/linux/iversion.h | 13 +++++++++++++
 2 files changed, 18 insertions(+), 8 deletions(-)

diff --git a/fs/nfsd/nfsfh.h b/fs/nfsd/nfsfh.h
index 39d764b129fa..45bd776290d5 100644
--- a/fs/nfsd/nfsfh.h
+++ b/fs/nfsd/nfsfh.h
@@ -259,19 +259,16 @@ fh_clear_wcc(struct svc_fh *fhp)
 static inline u64 nfsd4_change_attribute(struct kstat *stat,
 					 struct inode *inode)
 {
-	u64 chattr;
-
 	if (IS_I_VERSION(inode)) {
+		u64 chattr;
+
 		chattr =  stat->ctime.tv_sec;
 		chattr <<= 30;
 		chattr += stat->ctime.tv_nsec;
 		chattr += inode_query_iversion(inode);
-	} else {
-		chattr = stat->ctime.tv_sec;
-		chattr <<= 32;
-		chattr += stat->ctime.tv_nsec;
-	}
-	return chattr;
+		return chattr;
+	} else
+		return time_to_chattr(&stat->ctime);
 }
 
 extern void fill_pre_wcc(struct svc_fh *fhp);
diff --git a/include/linux/iversion.h b/include/linux/iversion.h
index 2917ef990d43..3bfebde5a1a6 100644
--- a/include/linux/iversion.h
+++ b/include/linux/iversion.h
@@ -328,6 +328,19 @@ inode_query_iversion(struct inode *inode)
 	return cur >> I_VERSION_QUERIED_SHIFT;
 }
 
+/*
+ * For filesystems without any sort of change attribute, the best we can
+ * do is fake one up from the ctime:
+ */
+static inline u64 time_to_chattr(struct timespec64 *t)
+{
+	u64 chattr = t->tv_sec;
+
+	chattr <<= 32;
+	chattr += t->tv_nsec;
+	return chattr;
+}
+
 /**
  * inode_eq_iversion_raw - check whether the raw i_version counter has changed
  * @inode: inode to check
-- 
2.28.0

[PATCH 4/5] nfsd4: don't query change attribute in v2/v3 case

[J. Bruce Fields]

From: "J. Bruce Fields" <bfields@redhat.com>

inode_query_iversion() has side effects, and there's no point calling it
when we're not even going to use it.

We check whether we're currently processing a v4 request by checking
fh_maxsize, which is arguably a little hacky; we could add a flag to
svc_fh instead.

Signed-off-by: J. Bruce Fields <bfields@redhat.com>
---
 fs/nfsd/nfs3xdr.c | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/fs/nfsd/nfs3xdr.c b/fs/nfsd/nfs3xdr.c
index dfbf390ff40c..f4fd54dc6965 100644
--- a/fs/nfsd/nfs3xdr.c
+++ b/fs/nfsd/nfs3xdr.c
@@ -259,11 +259,11 @@ void fill_pre_wcc(struct svc_fh *fhp)
 {
 	struct inode    *inode;
 	struct kstat	stat;
+	bool v4 = (fhp->fh_maxsize == NFS4_FHSIZE);
 	__be32 err;
 
 	if (fhp->fh_pre_saved)
 		return;
-
 	inode = d_inode(fhp->fh_dentry);
 	err = fh_getattr(fhp, &stat);
 	if (err) {
@@ -272,11 +272,12 @@ void fill_pre_wcc(struct svc_fh *fhp)
 		stat.ctime = inode->i_ctime;
 		stat.size  = inode->i_size;
 	}
+	if (v4)
+		fhp->fh_pre_change = nfsd4_change_attribute(&stat, inode);
 
 	fhp->fh_pre_mtime = stat.mtime;
 	fhp->fh_pre_ctime = stat.ctime;
 	fhp->fh_pre_size  = stat.size;
-	fhp->fh_pre_change = nfsd4_change_attribute(&stat, inode);
 	fhp->fh_pre_saved = true;
 }
 
@@ -285,6 +286,8 @@ void fill_pre_wcc(struct svc_fh *fhp)
  */
 void fill_post_wcc(struct svc_fh *fhp)
 {
+	bool v4 = (fhp->fh_maxsize == NFS4_FHSIZE);
+	struct inode *inode = d_inode(fhp->fh_dentry);
 	__be32 err;
 
 	if (fhp->fh_post_saved)
@@ -293,11 +296,12 @@ void fill_post_wcc(struct svc_fh *fhp)
 	err = fh_getattr(fhp, &fhp->fh_post_attr);
 	if (err) {
 		fhp->fh_post_saved = false;
-		fhp->fh_post_attr.ctime = d_inode(fhp->fh_dentry)->i_ctime;
+		fhp->fh_post_attr.ctime = inode->i_ctime;
 	} else
 		fhp->fh_post_saved = true;
-	fhp->fh_post_change = nfsd4_change_attribute(&fhp->fh_post_attr,
-						     d_inode(fhp->fh_dentry));
+	if (v4)
+		fhp->fh_post_change =
+			nfsd4_change_attribute(&fhp->fh_post_attr, inode);
 }
 
 /*
-- 
2.28.0

[PATCH 5/5] Revert "nfsd4: support change_attr_type attribute"

[J. Bruce Fields]

From: "J. Bruce Fields" <bfields@redhat.com>

This reverts commit a85857633b04d57f4524cca0a2bfaf87b2543f9f.

We're still factoring ctime into our change attribute even in the
IS_I_VERSION case.  If someone sets the system time backwards, a client
could see the change attribute go backwards.  Maybe we can just say
"well, don't do that", but there's some question whether that's good
enough, or whether we need a better guarantee.

Also, the client still isn't actually using the attribute.

While we're still figuring this out, let's just stop returning this
attribute.

Signed-off-by: J. Bruce Fields <bfields@redhat.com>
---
 fs/nfsd/nfs4xdr.c    | 10 ----------
 fs/nfsd/nfsd.h       |  1 -
 include/linux/nfs4.h |  8 --------
 3 files changed, 19 deletions(-)

diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
index 18c912930947..c33838caf8c6 100644
--- a/fs/nfsd/nfs4xdr.c
+++ b/fs/nfsd/nfs4xdr.c
@@ -3183,16 +3183,6 @@ nfsd4_encode_fattr(struct xdr_stream *xdr, struct svc_fh *fhp,
 			goto out;
 	}
 
-	if (bmval2 & FATTR4_WORD2_CHANGE_ATTR_TYPE) {
-		p = xdr_reserve_space(xdr, 4);
-		if (!p)
-			goto out_resource;
-		if (IS_I_VERSION(d_inode(dentry)))
-			*p++ = cpu_to_be32(NFS4_CHANGE_TYPE_IS_MONOTONIC_INCR);
-		else
-			*p++ = cpu_to_be32(NFS4_CHANGE_TYPE_IS_TIME_METADATA);
-	}
-
 #ifdef CONFIG_NFSD_V4_SECURITY_LABEL
 	if (bmval2 & FATTR4_WORD2_SECURITY_LABEL) {
 		status = nfsd4_encode_security_label(xdr, rqstp, context,
diff --git a/fs/nfsd/nfsd.h b/fs/nfsd/nfsd.h
index cb742e17e04a..40cb40ac0a65 100644
--- a/fs/nfsd/nfsd.h
+++ b/fs/nfsd/nfsd.h
@@ -387,7 +387,6 @@ void		nfsd_lockd_shutdown(void);
 
 #define NFSD4_2_SUPPORTED_ATTRS_WORD2 \
 	(NFSD4_1_SUPPORTED_ATTRS_WORD2 | \
-	FATTR4_WORD2_CHANGE_ATTR_TYPE | \
 	FATTR4_WORD2_MODE_UMASK | \
 	NFSD4_2_SECURITY_ATTRS | \
 	FATTR4_WORD2_XATTR_SUPPORT)
diff --git a/include/linux/nfs4.h b/include/linux/nfs4.h
index 9dc7eeac924f..5b4c67c91f56 100644
--- a/include/linux/nfs4.h
+++ b/include/linux/nfs4.h
@@ -385,13 +385,6 @@ enum lock_type4 {
 	NFS4_WRITEW_LT = 4
 };
 
-enum change_attr_type4 {
-	NFS4_CHANGE_TYPE_IS_MONOTONIC_INCR = 0,
-	NFS4_CHANGE_TYPE_IS_VERSION_COUNTER = 1,
-	NFS4_CHANGE_TYPE_IS_VERSION_COUNTER_NOPNFS = 2,
-	NFS4_CHANGE_TYPE_IS_TIME_METADATA = 3,
-	NFS4_CHANGE_TYPE_IS_UNDEFINED = 4
-};
 
 /* Mandatory Attributes */
 #define FATTR4_WORD0_SUPPORTED_ATTRS    (1UL << 0)
@@ -459,7 +452,6 @@ enum change_attr_type4 {
 #define FATTR4_WORD2_LAYOUT_BLKSIZE     (1UL << 1)
 #define FATTR4_WORD2_MDSTHRESHOLD       (1UL << 4)
 #define FATTR4_WORD2_CLONE_BLKSIZE	(1UL << 13)
-#define FATTR4_WORD2_CHANGE_ATTR_TYPE	(1UL << 15)
 #define FATTR4_WORD2_SECURITY_LABEL     (1UL << 16)
 #define FATTR4_WORD2_MODE_UMASK		(1UL << 17)
 #define FATTR4_WORD2_XATTR_SUPPORT	(1UL << 18)
-- 
2.28.0

Re: [PATCH 1/5] nfsd: only call inode_query_iversion in the I_VERSION case

[Jeff Layton]

On Mon, 2020-11-30 at 17:46 -0500, J. Bruce Fields wrote:
> From: "J. Bruce Fields" <bfields@redhat.com>
> 
> inode_query_iversion() can modify i_version.  Depending on the exported
> filesystem, that may not be safe.  For example, if you're re-exporting
> NFS, NFS stores the server's change attribute in i_version and does not
> expect it to be modified locally.  This has been observed causing
> unnecessary cache invalidations.
> 
> The way a filesystem indicates that it's OK to call
> inode_query_iverson() is by setting SB_I_VERSION.
> 
> So, move the I_VERSION check out of encode_change(), where it's used
> only in FATTR responses, to nfsd4_changeattr(), which is also called for
> pre- and post- operation attributes.
> 

"only in FATTR responses, to nfsd4_change_attribute(),"

> (Note we could also pull the NFSEXP_V4ROOT case into
> nfsd4_change_attribute as well.  That would actually be a no-op, since
> pre/post attrs are only used for metadata-modifying operations, and
> V4ROOT exports are read-only.  But we might make the change in the
> future just for simplicity.)
> 
> Reported-by: Daire Byrne <daire@dneg.com>
> Signed-off-by: J. Bruce Fields <bfields@redhat.com>
> ---
>  fs/nfsd/nfs3xdr.c |  5 ++---
>  fs/nfsd/nfs4xdr.c |  6 +-----
>  fs/nfsd/nfsfh.h   | 14 ++++++++++----
>  3 files changed, 13 insertions(+), 12 deletions(-)
> 
> diff --git a/fs/nfsd/nfs3xdr.c b/fs/nfsd/nfs3xdr.c
> index 2277f83da250..dfbf390ff40c 100644
> --- a/fs/nfsd/nfs3xdr.c
> +++ b/fs/nfsd/nfs3xdr.c
> @@ -291,14 +291,13 @@ void fill_post_wcc(struct svc_fh *fhp)
>  		printk("nfsd: inode locked twice during operation.\n");
>  
> 
> 
> 
>  	err = fh_getattr(fhp, &fhp->fh_post_attr);
> -	fhp->fh_post_change = nfsd4_change_attribute(&fhp->fh_post_attr,
> -						     d_inode(fhp->fh_dentry));
>  	if (err) {
>  		fhp->fh_post_saved = false;
> -		/* Grab the ctime anyway - set_change_info might use it */
>  		fhp->fh_post_attr.ctime = d_inode(fhp->fh_dentry)->i_ctime;
>  	} else
>  		fhp->fh_post_saved = true;
> +	fhp->fh_post_change = nfsd4_change_attribute(&fhp->fh_post_attr,
> +						     d_inode(fhp->fh_dentry));
>  }
>  
> 
> 
> 
>  /*
> diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
> index 833a2c64dfe8..56fd5f6d5c44 100644
> --- a/fs/nfsd/nfs4xdr.c
> +++ b/fs/nfsd/nfs4xdr.c
> @@ -2298,12 +2298,8 @@ static __be32 *encode_change(__be32 *p, struct kstat *stat, struct inode *inode,
>  	if (exp->ex_flags & NFSEXP_V4ROOT) {
>  		*p++ = cpu_to_be32(convert_to_wallclock(exp->cd->flush_time));
>  		*p++ = 0;
> -	} else if (IS_I_VERSION(inode)) {
> +	} else
>  		p = xdr_encode_hyper(p, nfsd4_change_attribute(stat, inode));
> -	} else {
> -		*p++ = cpu_to_be32(stat->ctime.tv_sec);
> -		*p++ = cpu_to_be32(stat->ctime.tv_nsec);
> -	}
>  	return p;
>  }
>  
> 
> 
> 
> diff --git a/fs/nfsd/nfsfh.h b/fs/nfsd/nfsfh.h
> index 56cfbc361561..39d764b129fa 100644
> --- a/fs/nfsd/nfsfh.h
> +++ b/fs/nfsd/nfsfh.h
> @@ -261,10 +261,16 @@ static inline u64 nfsd4_change_attribute(struct kstat *stat,
>  {
>  	u64 chattr;
>  
> 
> 
> 
> -	chattr =  stat->ctime.tv_sec;
> -	chattr <<= 30;
> -	chattr += stat->ctime.tv_nsec;
> -	chattr += inode_query_iversion(inode);
> +	if (IS_I_VERSION(inode)) {
> +		chattr =  stat->ctime.tv_sec;
> +		chattr <<= 30;
> +		chattr += stat->ctime.tv_nsec;
> +		chattr += inode_query_iversion(inode);
> +	} else {
> +		chattr = stat->ctime.tv_sec;
> +		chattr <<= 32;
> +		chattr += stat->ctime.tv_nsec;
> +	}
>  	return chattr;
>  }
>  
> 
> 
> 

-- 
Jeff Layton <jlayton@kernel.org>

Re: [PATCH 1/5] nfsd: only call inode_query_iversion in the I_VERSION case

[Jeff Layton]

On Mon, 2020-11-30 at 17:46 -0500, J. Bruce Fields wrote:
> From: "J. Bruce Fields" <bfields@redhat.com>
> 
> inode_query_iversion() can modify i_version.  Depending on the exported
> filesystem, that may not be safe.  For example, if you're re-exporting
> NFS, NFS stores the server's change attribute in i_version and does not
> expect it to be modified locally.  This has been observed causing
> unnecessary cache invalidations.
> 
> The way a filesystem indicates that it's OK to call
> inode_query_iverson() is by setting SB_I_VERSION.
> 
> So, move the I_VERSION check out of encode_change(), where it's used
> only in FATTR responses, to nfsd4_changeattr(), which is also called for
> pre- and post- operation attributes.
> 
> (Note we could also pull the NFSEXP_V4ROOT case into
> nfsd4_change_attribute as well.  That would actually be a no-op, since
> pre/post attrs are only used for metadata-modifying operations, and
> V4ROOT exports are read-only.  But we might make the change in the
> future just for simplicity.)
> 
> Reported-by: Daire Byrne <daire@dneg.com>
> Signed-off-by: J. Bruce Fields <bfields@redhat.com>
> ---
>  fs/nfsd/nfs3xdr.c |  5 ++---
>  fs/nfsd/nfs4xdr.c |  6 +-----
>  fs/nfsd/nfsfh.h   | 14 ++++++++++----
>  3 files changed, 13 insertions(+), 12 deletions(-)
> 
> diff --git a/fs/nfsd/nfs3xdr.c b/fs/nfsd/nfs3xdr.c
> index 2277f83da250..dfbf390ff40c 100644
> --- a/fs/nfsd/nfs3xdr.c
> +++ b/fs/nfsd/nfs3xdr.c
> @@ -291,14 +291,13 @@ void fill_post_wcc(struct svc_fh *fhp)
>  		printk("nfsd: inode locked twice during operation.\n");
>  
> 
> 
> 
>  	err = fh_getattr(fhp, &fhp->fh_post_attr);
> -	fhp->fh_post_change = nfsd4_change_attribute(&fhp->fh_post_attr,
> -						     d_inode(fhp->fh_dentry));
>  	if (err) {
>  		fhp->fh_post_saved = false;
> -		/* Grab the ctime anyway - set_change_info might use it */
>  		fhp->fh_post_attr.ctime = d_inode(fhp->fh_dentry)->i_ctime;
>  	} else
>  		fhp->fh_post_saved = true;
> +	fhp->fh_post_change = nfsd4_change_attribute(&fhp->fh_post_attr,
> +						     d_inode(fhp->fh_dentry));
>  }
>  
> 
> 
> 
>  /*
> diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
> index 833a2c64dfe8..56fd5f6d5c44 100644
> --- a/fs/nfsd/nfs4xdr.c
> +++ b/fs/nfsd/nfs4xdr.c
> @@ -2298,12 +2298,8 @@ static __be32 *encode_change(__be32 *p, struct kstat *stat, struct inode *inode,
>  	if (exp->ex_flags & NFSEXP_V4ROOT) {
>  		*p++ = cpu_to_be32(convert_to_wallclock(exp->cd->flush_time));
>  		*p++ = 0;
> -	} else if (IS_I_VERSION(inode)) {
> +	} else
>  		p = xdr_encode_hyper(p, nfsd4_change_attribute(stat, inode));
> -	} else {
> -		*p++ = cpu_to_be32(stat->ctime.tv_sec);
> -		*p++ = cpu_to_be32(stat->ctime.tv_nsec);
> -	}
>  	return p;
>  }
>  
> 
> 
> 
> diff --git a/fs/nfsd/nfsfh.h b/fs/nfsd/nfsfh.h
> index 56cfbc361561..39d764b129fa 100644
> --- a/fs/nfsd/nfsfh.h
> +++ b/fs/nfsd/nfsfh.h
> @@ -261,10 +261,16 @@ static inline u64 nfsd4_change_attribute(struct kstat *stat,
>  {
>  	u64 chattr;
>  
> 
> 
> 
> -	chattr =  stat->ctime.tv_sec;
> -	chattr <<= 30;
> -	chattr += stat->ctime.tv_nsec;
> -	chattr += inode_query_iversion(inode);
> +	if (IS_I_VERSION(inode)) {
> +		chattr =  stat->ctime.tv_sec;
> +		chattr <<= 30;
> +		chattr += stat->ctime.tv_nsec;
> +		chattr += inode_query_iversion(inode);
> +	} else {
> +		chattr = stat->ctime.tv_sec;
> +		chattr <<= 32;

Might be nice to annotate the shifts above and maybe make them named
constants. I'm not sure where those values come from, tbh.

> +		chattr += stat->ctime.tv_nsec;
> +	}
>  	return chattr;
>  }
>  
> 
> 
> 


Other than some very minor nits, the set itself looks great.

Are you planning to follow up with the series to add the fetch_iversion
op, or have you decided not to do that for now?

Reviewed-by: Jeff Layton <jlayton@kernel.org>

Re: [PATCH 1/5] nfsd: only call inode_query_iversion in the I_VERSION case

[J. Bruce Fields]

On Tue, Dec 01, 2020 at 11:30:12AM -0500, Jeff Layton wrote:
> On Mon, 2020-11-30 at 17:46 -0500, J. Bruce Fields wrote:
> > From: "J. Bruce Fields" <bfields@redhat.com>
> > 
> > inode_query_iversion() can modify i_version.  Depending on the exported
> > filesystem, that may not be safe.  For example, if you're re-exporting
> > NFS, NFS stores the server's change attribute in i_version and does not
> > expect it to be modified locally.  This has been observed causing
> > unnecessary cache invalidations.
> > 
> > The way a filesystem indicates that it's OK to call
> > inode_query_iverson() is by setting SB_I_VERSION.
> > 
> > So, move the I_VERSION check out of encode_change(), where it's used
> > only in FATTR responses, to nfsd4_changeattr(), which is also called for
> > pre- and post- operation attributes.
> > 
> 
> "only in FATTR responses, to nfsd4_change_attribute(),"

Whoops, and also FATTR should have been GETATTR.

Fixed locally, I assume Chuck will just want to fix that up in his tree
(let me know if not).

--b.

Re: [PATCH 1/5] nfsd: only call inode_query_iversion in the I_VERSION case

[J. Bruce Fields]

On Tue, Dec 01, 2020 at 11:43:31AM -0500, Jeff Layton wrote:
> On Mon, 2020-11-30 at 17:46 -0500, J. Bruce Fields wrote:
> > From: "J. Bruce Fields" <bfields@redhat.com>
> > 
> > inode_query_iversion() can modify i_version.  Depending on the exported
> > filesystem, that may not be safe.  For example, if you're re-exporting
> > NFS, NFS stores the server's change attribute in i_version and does not
> > expect it to be modified locally.  This has been observed causing
> > unnecessary cache invalidations.
> > 
> > The way a filesystem indicates that it's OK to call
> > inode_query_iverson() is by setting SB_I_VERSION.
> > 
> > So, move the I_VERSION check out of encode_change(), where it's used
> > only in FATTR responses, to nfsd4_changeattr(), which is also called for
> > pre- and post- operation attributes.
> > 
> > (Note we could also pull the NFSEXP_V4ROOT case into
> > nfsd4_change_attribute as well.  That would actually be a no-op, since
> > pre/post attrs are only used for metadata-modifying operations, and
> > V4ROOT exports are read-only.  But we might make the change in the
> > future just for simplicity.)
> > 
> > Reported-by: Daire Byrne <daire@dneg.com>
> > Signed-off-by: J. Bruce Fields <bfields@redhat.com>
> > ---
> >  fs/nfsd/nfs3xdr.c |  5 ++---
> >  fs/nfsd/nfs4xdr.c |  6 +-----
> >  fs/nfsd/nfsfh.h   | 14 ++++++++++----
> >  3 files changed, 13 insertions(+), 12 deletions(-)
> > 
> > diff --git a/fs/nfsd/nfs3xdr.c b/fs/nfsd/nfs3xdr.c
> > index 2277f83da250..dfbf390ff40c 100644
> > --- a/fs/nfsd/nfs3xdr.c
> > +++ b/fs/nfsd/nfs3xdr.c
> > @@ -291,14 +291,13 @@ void fill_post_wcc(struct svc_fh *fhp)
> >  		printk("nfsd: inode locked twice during operation.\n");
> >  
> > 
> > 
> > 
> >  	err = fh_getattr(fhp, &fhp->fh_post_attr);
> > -	fhp->fh_post_change = nfsd4_change_attribute(&fhp->fh_post_attr,
> > -						     d_inode(fhp->fh_dentry));
> >  	if (err) {
> >  		fhp->fh_post_saved = false;
> > -		/* Grab the ctime anyway - set_change_info might use it */
> >  		fhp->fh_post_attr.ctime = d_inode(fhp->fh_dentry)->i_ctime;
> >  	} else
> >  		fhp->fh_post_saved = true;
> > +	fhp->fh_post_change = nfsd4_change_attribute(&fhp->fh_post_attr,
> > +						     d_inode(fhp->fh_dentry));
> >  }
> >  
> > 
> > 
> > 
> >  /*
> > diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
> > index 833a2c64dfe8..56fd5f6d5c44 100644
> > --- a/fs/nfsd/nfs4xdr.c
> > +++ b/fs/nfsd/nfs4xdr.c
> > @@ -2298,12 +2298,8 @@ static __be32 *encode_change(__be32 *p, struct kstat *stat, struct inode *inode,
> >  	if (exp->ex_flags & NFSEXP_V4ROOT) {
> >  		*p++ = cpu_to_be32(convert_to_wallclock(exp->cd->flush_time));
> >  		*p++ = 0;
> > -	} else if (IS_I_VERSION(inode)) {
> > +	} else
> >  		p = xdr_encode_hyper(p, nfsd4_change_attribute(stat, inode));
> > -	} else {
> > -		*p++ = cpu_to_be32(stat->ctime.tv_sec);
> > -		*p++ = cpu_to_be32(stat->ctime.tv_nsec);
> > -	}
> >  	return p;
> >  }
> >  
> > 
> > 
> > 
> > diff --git a/fs/nfsd/nfsfh.h b/fs/nfsd/nfsfh.h
> > index 56cfbc361561..39d764b129fa 100644
> > --- a/fs/nfsd/nfsfh.h
> > +++ b/fs/nfsd/nfsfh.h
> > @@ -261,10 +261,16 @@ static inline u64 nfsd4_change_attribute(struct kstat *stat,
> >  {
> >  	u64 chattr;
> >  
> > 
> > 
> > 
> > -	chattr =  stat->ctime.tv_sec;
> > -	chattr <<= 30;
> > -	chattr += stat->ctime.tv_nsec;
> > -	chattr += inode_query_iversion(inode);
> > +	if (IS_I_VERSION(inode)) {
> > +		chattr =  stat->ctime.tv_sec;
> > +		chattr <<= 30;
> > +		chattr += stat->ctime.tv_nsec;
> > +		chattr += inode_query_iversion(inode);
> > +	} else {
> > +		chattr = stat->ctime.tv_sec;
> > +		chattr <<= 32;
> 
> Might be nice to annotate the shifts above and maybe make them named
> constants. I'm not sure where those values come from, tbh.

This shouldn't be changing the on-the-wire results at all; so
for example the latter is just doing exactly what:

> > -		*p++ = cpu_to_be32(stat->ctime.tv_sec);
> > -		*p++ = cpu_to_be32(stat->ctime.tv_nsec);

did (after xdr-encoding of the 64-bit chattr).

But yeah maybe it could use some explanation.

The 30-bit shift in the IS_I_VERSION case is weirder, I honestly don't
remember what I was thinking.  Maybe just that nanoseconds really only
need 30 bits, and the shift would save a couple high bits in case we
wanted to change the format later without making the change attribute go
backwards.  Probably overthinking it!

--b.

Re: [PATCH 1/5] nfsd: only call inode_query_iversion in the I_VERSION case

[J. Bruce Fields]

On Tue, Dec 01, 2020 at 11:43:31AM -0500, Jeff Layton wrote:
> Are you planning to follow up with the series to add the fetch_iversion
> op, or have you decided not to do that for now?

I'm still interested.  I just figured it's not urgent, and it'll be
easier to ask for fs-devel review after this other stuff is in, so it
may as well wait till after the merge window.

--b.