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

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> On Nov 30, 2020, at 2:38 PM, J. Bruce Fields <bfields@xxxxxxxxxxxx> wrote:
> 
> From: "J. Bruce Fields" <bfields@xxxxxxxxxx>
> 
> 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@xxxxxxxx>
> Signed-off-by: J. Bruce Fields <bfields@xxxxxxxxxx>

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







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