Re: [PATCH v2 15/18] nfsd: Add I/O trace points in the NFSv4 read proc

[Bruce Fields <bfields@fieldses.org>]

Could you check that I got this right in

	git://linux-nfs.org/~bfields/linux.git nfsd-next

--b.

On Tue, Mar 27, 2018 at 12:57:17PM -0400, Chuck Lever wrote:
> 
> 
> > On Mar 27, 2018, at 10:53 AM, Chuck Lever <chuck.lever@oracle.com> wrote:
> > 
> > NFSv4 read compound processing invokes nfsd_splice_read and
> > nfs_readv directly, so the trace points currently in nfsd_read are
> > not effective for NFSv4 reads.
> > 
> > Move and copy the trace points so that NFSv4 reads are captured.
> > Also, we want to record any local I/O error that occurs, and
> > the total count of bytes that were actually moved. And, also
> > whether splice or vectored read was used.
> > 
> > The svc_fh is not passed to the read helpers, so some code
> > duplication is necessary.
> > 
> > Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
> > ---
> > fs/nfsd/nfs4proc.c |    5 +++++
> > fs/nfsd/nfs4xdr.c  |   56 +++++++++++++++++++++++++++++++++++++---------------
> > fs/nfsd/trace.h    |    4 +++-
> > fs/nfsd/vfs.c      |   54 ++++++++++++++++++++++----------------------------
> > fs/nfsd/vfs.h      |    8 ++++---
> > 5 files changed, 76 insertions(+), 51 deletions(-)
> > 
> > diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
> > index b93673e..39016b6 100644
> > --- a/fs/nfsd/nfs4proc.c
> > +++ b/fs/nfsd/nfs4proc.c
> > @@ -751,6 +751,9 @@ static __be32 nfsd4_do_lookupp(struct svc_rqst *rqstp, struct svc_fh *fh)
> > 	if (read->rd_offset >= OFFSET_MAX)
> > 		return nfserr_inval;
> > 
> > +	trace_nfsd_read_start(rqstp, &cstate->current_fh,
> > +			      read->rd_offset, read->rd_length);
> > +
> > 	/*
> > 	 * If we do a zero copy read, then a client will see read data
> > 	 * that reflects the state of the file *after* performing the
> > @@ -783,6 +786,8 @@ static __be32 nfsd4_do_lookupp(struct svc_rqst *rqstp, struct svc_fh *fh)
> > {
> > 	if (u->read.rd_filp)
> > 		fput(u->read.rd_filp);
> > +	trace_nfsd_read_done(u->read.rd_rqstp, u->read.rd_fhp,
> > +			     u->read.rd_offset, u->read.rd_length);
> > }
> > 
> > static __be32
> > diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
> > index e502fd1..d03059a 100644
> > --- a/fs/nfsd/nfs4xdr.c
> > +++ b/fs/nfsd/nfs4xdr.c
> > @@ -37,6 +37,7 @@
> > #include <linux/file.h>
> > #include <linux/slab.h>
> > #include <linux/namei.h>
> > +#include <linux/fsnotify.h>
> > #include <linux/statfs.h>
> > #include <linux/utsname.h>
> > #include <linux/pagemap.h>
> > @@ -50,6 +51,7 @@
> > #include "cache.h"
> > #include "netns.h"
> > #include "pnfs.h"
> > +#include "trace.h"
> > 
> > #ifdef CONFIG_NFSD_V4_SECURITY_LABEL
> > #include <linux/security.h>
> > @@ -3416,28 +3418,28 @@ static __be32 nfsd4_encode_splice_read(
> > {
> > 	struct xdr_stream *xdr = &resp->xdr;
> > 	struct xdr_buf *buf = xdr->buf;
> > +	int host_err;
> > 	u32 eof;
> > 	long len;
> > 	int space_left;
> > -	__be32 nfserr;
> > 	__be32 *p = xdr->p - 2;
> > 
> > 	/* Make sure there will be room for padding if needed */
> > 	if (xdr->end - xdr->p < 1)
> > 		return nfserr_resource;
> > 
> > +	trace_nfsd_read_splice(resp->rqstp, read->rd_fhp,
> > +			       read->rd_offset, maxcount);
> > 	len = maxcount;
> > -	nfserr = nfsd_splice_read(read->rd_rqstp, file,
> > +	host_err = nfsd_splice_read(read->rd_rqstp, file,
> > 				  read->rd_offset, &maxcount);
> > -	if (nfserr) {
> > -		/*
> > -		 * nfsd_splice_actor may have already messed with the
> > -		 * page length; reset it so as not to confuse
> > -		 * xdr_truncate_encode:
> > -		 */
> > -		buf->page_len = 0;
> > -		return nfserr;
> > -	}
> > +	if (host_err < 0)
> > +		goto err;
> > +	trace_nfsd_read_io_done(read->rd_rqstp, read->rd_fhp,
> > +				read->rd_offset, maxcount);
> > +	maxcount = host_err;
> > +	nfsdstats.io_read += maxcount;
> > +	fsnotify_access(file);
> > 
> > 	eof = nfsd_eof_on_read(len, maxcount, read->rd_offset,
> > 				d_inode(read->rd_fhp->fh_dentry)->i_size);
> > @@ -3470,6 +3472,17 @@ static __be32 nfsd4_encode_splice_read(
> > 	xdr->end = (__be32 *)((void *)xdr->end + space_left);
> > 
> > 	return 0;
> > +
> > +err:
> > +	/*
> > +	 * nfsd_splice_actor may have already messed with the
> > +	 * page length; reset it so as not to confuse
> > +	 * xdr_truncate_encode:
> > +	 */
> > +	buf->page_len = 0;
> > +	trace_nfsd_read_err(read->rd_rqstp, read->rd_fhp,
> > +			    read->rd_offset, host_err);
> > +	return nfserrno(host_err);
> > }
> > 
> > static __be32 nfsd4_encode_readv(struct nfsd4_compoundres *resp,
> > @@ -3477,12 +3490,12 @@ static __be32 nfsd4_encode_readv(struct nfsd4_compoundres *resp,
> > 				 struct file *file, unsigned long maxcount)
> > {
> > 	struct xdr_stream *xdr = &resp->xdr;
> > +	int host_err;
> > 	u32 eof;
> > 	int v;
> > 	int starting_len = xdr->buf->len - 8;
> > 	long len;
> > 	int thislen;
> > -	__be32 nfserr;
> > 	__be32 tmp;
> > 	__be32 *p;
> > 	u32 zzz = 0;
> > @@ -3510,11 +3523,18 @@ static __be32 nfsd4_encode_readv(struct nfsd4_compoundres *resp,
> > 	}
> > 	read->rd_vlen = v;
> > 
> > +	trace_nfsd_read_vector(resp->rqstp, read->rd_fhp,
> > +			       read->rd_offset, maxcount);
> > 	len = maxcount;
> > -	nfserr = nfsd_readv(file, read->rd_offset, resp->rqstp->rq_vec,
> > -			read->rd_vlen, &maxcount);
> > -	if (nfserr)
> > -		return nfserr;
> > +	host_err = nfsd_readv(file, read->rd_offset, resp->rqstp->rq_vec,
> > +			      read->rd_vlen, &maxcount);
> > +	if (host_err < 0)
> > +		goto err;
> > +	trace_nfsd_read_io_done(resp->rqstp, read->rd_fhp,
> > +				read->rd_offset, maxcount);
> 
> I missed a spot.
> 
> +	maxcount = host_err;
> 
> > +	nfsdstats.io_read += maxcount;
> > +	fsnotify_access(file);
> > +
> > 	xdr_truncate_encode(xdr, starting_len + 8 + ((maxcount+3)&~3));
> > 
> > 	eof = nfsd_eof_on_read(len, maxcount, read->rd_offset,
> > @@ -3530,6 +3550,10 @@ static __be32 nfsd4_encode_readv(struct nfsd4_compoundres *resp,
> > 								&zzz, pad);
> > 	return 0;
> > 
> > +err:
> > +	trace_nfsd_read_err(resp->rqstp, read->rd_fhp,
> > +			    read->rd_offset, host_err);
> > +	return nfserrno(host_err);
> > }
> > 
> > static __be32
> > diff --git a/fs/nfsd/trace.h b/fs/nfsd/trace.h
> > index 653e9ee..a8bbd9d 100644
> > --- a/fs/nfsd/trace.h
> > +++ b/fs/nfsd/trace.h
> > @@ -43,7 +43,8 @@
> > 	TP_ARGS(rqstp, fhp, offset, len))
> > 
> > DEFINE_NFSD_IO_EVENT(read_start);
> > -DEFINE_NFSD_IO_EVENT(read_opened);
> > +DEFINE_NFSD_IO_EVENT(read_splice);
> > +DEFINE_NFSD_IO_EVENT(read_vector);
> > DEFINE_NFSD_IO_EVENT(read_io_done);
> > DEFINE_NFSD_IO_EVENT(read_done);
> > DEFINE_NFSD_IO_EVENT(write_start);
> > @@ -82,6 +83,7 @@
> > 		 int		len),		\
> > 	TP_ARGS(rqstp, fhp, offset, len))
> > 
> > +DEFINE_NFSD_ERR_EVENT(read_err);
> > DEFINE_NFSD_ERR_EVENT(write_err);
> > 
> > #include "state.h"
> > diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
> > index ee59a0b..0fa54b5 100644
> > --- a/fs/nfsd/vfs.c
> > +++ b/fs/nfsd/vfs.c
> > @@ -881,19 +881,7 @@ static int nfsd_direct_splice_actor(struct pipe_inode_info *pipe,
> > 	return __splice_from_pipe(pipe, sd, nfsd_splice_actor);
> > }
> > 
> > -static __be32
> > -nfsd_finish_read(struct file *file, unsigned long *count, int host_err)
> > -{
> > -	if (host_err >= 0) {
> > -		nfsdstats.io_read += host_err;
> > -		*count = host_err;
> > -		fsnotify_access(file);
> > -		return 0;
> > -	} else 
> > -		return nfserrno(host_err);
> > -}
> > -
> > -__be32 nfsd_splice_read(struct svc_rqst *rqstp,
> > +int nfsd_splice_read(struct svc_rqst *rqstp,
> > 		     struct file *file, loff_t offset, unsigned long *count)
> > {
> > 	struct splice_desc sd = {
> > @@ -902,23 +890,18 @@ __be32 nfsd_splice_read(struct svc_rqst *rqstp,
> > 		.pos		= offset,
> > 		.u.data		= rqstp,
> > 	};
> > -	int host_err;
> > 
> > 	rqstp->rq_next_page = rqstp->rq_respages + 1;
> > -	host_err = splice_direct_to_actor(file, &sd, nfsd_direct_splice_actor);
> > -	return nfsd_finish_read(file, count, host_err);
> > +	return splice_direct_to_actor(file, &sd, nfsd_direct_splice_actor);
> > }
> > 
> > -__be32 nfsd_readv(struct file *file, loff_t offset, struct kvec *vec, int vlen,
> > -		unsigned long *count)
> > +int nfsd_readv(struct file *file, loff_t offset, struct kvec *vec, int vlen,
> > +	       unsigned long *count)
> > {
> > 	struct iov_iter iter;
> > -	int host_err;
> > 
> > 	iov_iter_kvec(&iter, READ | ITER_KVEC, vec, vlen, *count);
> > -	host_err = vfs_iter_read(file, &iter, &offset, 0);
> > -
> > -	return nfsd_finish_read(file, count, host_err);
> > +	return vfs_iter_read(file, &iter, &offset, 0);
> > }
> > 
> > /*
> > @@ -1025,6 +1008,7 @@ __be32 nfsd_read(struct svc_rqst *rqstp, struct svc_fh *fhp,
> > {
> > 	struct file *file;
> > 	struct raparms	*ra;
> > +	int host_err;
> > 	__be32 err;
> > 
> > 	trace_nfsd_read_start(rqstp, fhp, offset, *count);
> > @@ -1034,14 +1018,24 @@ __be32 nfsd_read(struct svc_rqst *rqstp, struct svc_fh *fhp,
> > 
> > 	ra = nfsd_init_raparms(file);
> > 
> > -	trace_nfsd_read_opened(rqstp, fhp, offset, *count);
> > -
> > -	if (file->f_op->splice_read && test_bit(RQ_SPLICE_OK, &rqstp->rq_flags))
> > -		err = nfsd_splice_read(rqstp, file, offset, count);
> > -	else
> > -		err = nfsd_readv(file, offset, vec, vlen, count);
> > -
> > -	trace_nfsd_read_io_done(rqstp, fhp, offset, *count);
> > +	if (file->f_op->splice_read &&
> > +	    test_bit(RQ_SPLICE_OK, &rqstp->rq_flags)) {
> > +		trace_nfsd_read_splice(rqstp, fhp, offset, *count);
> > +		host_err = nfsd_splice_read(rqstp, file, offset, count);
> > +	} else {
> > +		trace_nfsd_read_vector(rqstp, fhp, offset, *count);
> > +		host_err = nfsd_readv(file, offset, vec, vlen, count);
> > +	}
> > +	if (host_err >= 0) {
> > +		trace_nfsd_read_io_done(rqstp, fhp, offset, host_err);
> > +		nfsdstats.io_read += host_err;
> > +		*count = host_err;
> > +		fsnotify_access(file);
> > +		err = nfs_ok;
> > +	} else  {
> > +		trace_nfsd_read_err(rqstp, fhp, offset, host_err);
> > +		err = nfserrno(host_err);
> > +	}
> > 
> > 	if (ra)
> > 		nfsd_put_raparams(file, ra);
> > diff --git a/fs/nfsd/vfs.h b/fs/nfsd/vfs.h
> > index be6d8e0..d9131c3 100644
> > --- a/fs/nfsd/vfs.h
> > +++ b/fs/nfsd/vfs.h
> > @@ -78,10 +78,10 @@ __be32		nfsd_commit(struct svc_rqst *, struct svc_fh *,
> > __be32		nfsd_open(struct svc_rqst *, struct svc_fh *, umode_t,
> > 				int, struct file **);
> > struct raparms;
> > -__be32		nfsd_splice_read(struct svc_rqst *,
> > -				struct file *, loff_t, unsigned long *);
> > -__be32		nfsd_readv(struct file *, loff_t, struct kvec *, int,
> > -				unsigned long *);
> > +int		nfsd_splice_read(struct svc_rqst *rqstp, struct file *file,
> > +				loff_t offset, unsigned long *count);
> > +int		nfsd_readv(struct file *file, loff_t offset, struct kvec *vec,
> > +				int vlen, unsigned long *count);
> > __be32 		nfsd_read(struct svc_rqst *, struct svc_fh *,
> > 				loff_t, struct kvec *, int, unsigned long *);
> > __be32 		nfsd_write(struct svc_rqst *, struct svc_fh *, loff_t,
> > 
> > --
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> 
> --
> Chuck Lever
> 
>