diff mbox series

[RFC,03/12] netfs: Remove netfs_read_subrequest::transferred

Message ID 162687511125.276387.15493860267582539643.stgit@warthog.procyon.org.uk
State New
Headers show
Series [RFC,01/12] afs: Sort out symlink reading | expand

Commit Message

David Howells July 21, 2021, 1:45 p.m. UTC 
Remove netfs_read_subrequest::transferred as it's redundant as the count on
the iterator added to the subrequest can be used instead.

Signed-off-by: David Howells <dhowells@redhat.com>
---

 fs/afs/file.c                |    4 ++--
 fs/netfs/read_helper.c       |   26 ++++----------------------
 include/linux/netfs.h        |    1 -
 include/trace/events/netfs.h |   12 ++++++------
 4 files changed, 12 insertions(+), 31 deletions(-)

Comments

Jeff Layton July 21, 2021, 7 p.m. UTC | #1 
On Wed, 2021-07-21 at 19:54 +0100, David Howells wrote:
> Jeff Layton <jlayton@redhat.com> wrote:
> 
> > The above two deltas seem like they should have been in patch #2.
> 
> Yeah.  Looks like at least partially so.
> 
> > > @@ -635,15 +625,8 @@ void netfs_subreq_terminated(struct netfs_read_subrequest *subreq,
> > >  		goto failed;
> > >  	}
> > >  
> > > -	if (WARN(transferred_or_error > subreq->len - subreq->transferred,
> > > -		 "Subreq overread: R%x[%x] %zd > %zu - %zu",
> > > -		 rreq->debug_id, subreq->debug_index,
> > > -		 transferred_or_error, subreq->len, subreq->transferred))
> > > -		transferred_or_error = subreq->len - subreq->transferred;
> > > -
> > >  	subreq->error = 0;
> > > -	subreq->transferred += transferred_or_error;
> > > -	if (subreq->transferred < subreq->len)
> > > +	if (iov_iter_count(&subreq->iter))
> > >  		goto incomplete;
> > >  
> > 
> > I must be missing it, but where does subreq->iter get advanced to the
> > end of the current read? If you're getting rid of subreq->transferred
> > then I think that has to happen above, no?
> 
> For afs, afs_req_issue_op() points fsreq->iter at the subrequest iterator and
> calls afs_fetch_data().  Thereafter, we wend our way to
> afs_deliver_fs_fetch_data() or yfs_deliver_fs_fetch_data() which set
> call->iter to point to that iterator and then call afs_extract_data() which
> passes it to rxrpc_kernel_recv_data(), which eventually passes it to
> skb_copy_datagram_iter(), which advances the iterator.
> 
> For the cache, the subrequest iterator is passed to the cache backend by
> netfs_read_from_cache().  This would be cachefiles_read() which calls
> vfs_iocb_iter_read() which I thought advances the iterator (leastways,
> filemap_read() keeps going until iov_iter_count() reaches 0 or some other stop
> condition occurs and doesn't thereafter call iov_iter_revert()).
> 

Ok, this will probably regress ceph then. We don't really have anything
to do with the subreq->iter at this point and this patch doesn't change
that. If you're going to make this change, it'd be cleaner to also fix
up ceph_netfs_issue_op to advance the iter at the same time.
diff mbox series

Patch

diff --git a/fs/afs/file.c b/fs/afs/file.c
index ca529f23515a..82e945dbe379 100644
--- a/fs/afs/file.c
+++ b/fs/afs/file.c
@@ -315,8 +315,8 @@  static void afs_req_issue_op(struct netfs_read_subrequest *subreq)
 		return netfs_subreq_terminated(subreq, -ENOMEM, false);
 
 	fsreq->subreq	= subreq;
-	fsreq->pos	= subreq->start + subreq->transferred;
-	fsreq->len	= subreq->len   - subreq->transferred;
+	fsreq->pos	= subreq->start + subreq->len - iov_iter_count(&subreq->iter);
+	fsreq->len	= iov_iter_count(&subreq->iter);
 	fsreq->key	= subreq->rreq->netfs_priv;
 	fsreq->vnode	= vnode;
 	fsreq->iter	= &subreq->iter;
diff --git a/fs/netfs/read_helper.c b/fs/netfs/read_helper.c
index 715f3e9c380d..5e1a9be48130 100644
--- a/fs/netfs/read_helper.c
+++ b/fs/netfs/read_helper.c
@@ -148,12 +148,7 @@  static void __netfs_put_subrequest(struct netfs_read_subrequest *subreq,
  */
 static void netfs_clear_unread(struct netfs_read_subrequest *subreq)
 {
-	struct iov_iter iter;
-
-	iov_iter_xarray(&iter, READ, &subreq->rreq->mapping->i_pages,
-			subreq->start + subreq->transferred,
-			subreq->len   - subreq->transferred);
-	iov_iter_zero(iov_iter_count(&iter), &iter);
+	iov_iter_zero(iov_iter_count(&subreq->iter), &subreq->iter);
 }
 
 static void netfs_cache_read_terminated(void *priv, ssize_t transferred_or_error,
@@ -173,14 +168,9 @@  static void netfs_read_from_cache(struct netfs_read_request *rreq,
 				  bool seek_data)
 {
 	struct netfs_cache_resources *cres = &rreq->cache_resources;
-	struct iov_iter iter;
 
 	netfs_stat(&netfs_n_rh_read);
-	iov_iter_xarray(&iter, READ, &rreq->mapping->i_pages,
-			subreq->start + subreq->transferred,
-			subreq->len   - subreq->transferred);
-
-	cres->ops->read(cres, subreq->start, &iter, seek_data,
+	cres->ops->read(cres, subreq->start, &subreq->iter, seek_data,
 			netfs_cache_read_terminated, subreq);
 }
 
@@ -419,7 +409,7 @@  static void netfs_rreq_unlock(struct netfs_read_request *rreq)
 			if (pgend < iopos + subreq->len)
 				break;
 
-			account += subreq->transferred;
+			account += subreq->len - iov_iter_count(&subreq->iter);
 			iopos += subreq->len;
 			if (!list_is_last(&subreq->rreq_link, &rreq->subrequests)) {
 				subreq = list_next_entry(subreq, rreq_link);
@@ -635,15 +625,8 @@  void netfs_subreq_terminated(struct netfs_read_subrequest *subreq,
 		goto failed;
 	}
 
-	if (WARN(transferred_or_error > subreq->len - subreq->transferred,
-		 "Subreq overread: R%x[%x] %zd > %zu - %zu",
-		 rreq->debug_id, subreq->debug_index,
-		 transferred_or_error, subreq->len, subreq->transferred))
-		transferred_or_error = subreq->len - subreq->transferred;
-
 	subreq->error = 0;
-	subreq->transferred += transferred_or_error;
-	if (subreq->transferred < subreq->len)
+	if (iov_iter_count(&subreq->iter))
 		goto incomplete;
 
 complete:
@@ -667,7 +650,6 @@  void netfs_subreq_terminated(struct netfs_read_subrequest *subreq,
 incomplete:
 	if (test_bit(NETFS_SREQ_CLEAR_TAIL, &subreq->flags)) {
 		netfs_clear_unread(subreq);
-		subreq->transferred = subreq->len;
 		goto complete;
 	}
 
diff --git a/include/linux/netfs.h b/include/linux/netfs.h
index 5e4fafcc9480..45d40c622205 100644
--- a/include/linux/netfs.h
+++ b/include/linux/netfs.h
@@ -116,7 +116,6 @@  struct netfs_read_subrequest {
 	struct iov_iter		iter;		/* Iterator for this subrequest */
 	loff_t			start;		/* Where to start the I/O */
 	size_t			len;		/* Size of the I/O */
-	size_t			transferred;	/* Amount of data transferred */
 	refcount_t		usage;
 	short			error;		/* 0 or error that occurred */
 	unsigned short		debug_index;	/* Index in list (for debugging output) */
diff --git a/include/trace/events/netfs.h b/include/trace/events/netfs.h
index 4d470bffd9f1..04ac29fc700f 100644
--- a/include/trace/events/netfs.h
+++ b/include/trace/events/netfs.h
@@ -190,7 +190,7 @@  TRACE_EVENT(netfs_sreq,
 		    __field(enum netfs_read_source,	source		)
 		    __field(enum netfs_sreq_trace,	what		)
 		    __field(size_t,			len		)
-		    __field(size_t,			transferred	)
+		    __field(size_t,			remain		)
 		    __field(loff_t,			start		)
 			     ),
 
@@ -202,7 +202,7 @@  TRACE_EVENT(netfs_sreq,
 		    __entry->source	= sreq->source;
 		    __entry->what	= what;
 		    __entry->len	= sreq->len;
-		    __entry->transferred = sreq->transferred;
+		    __entry->remain	= iov_iter_count(&sreq->iter);
 		    __entry->start	= sreq->start;
 			   ),
 
@@ -211,7 +211,7 @@  TRACE_EVENT(netfs_sreq,
 		      __print_symbolic(__entry->what, netfs_sreq_traces),
 		      __print_symbolic(__entry->source, netfs_sreq_sources),
 		      __entry->flags,
-		      __entry->start, __entry->transferred, __entry->len,
+		      __entry->start, __entry->len - __entry->remain, __entry->len,
 		      __entry->error)
 	    );
 
@@ -230,7 +230,7 @@  TRACE_EVENT(netfs_failure,
 		    __field(enum netfs_read_source,	source		)
 		    __field(enum netfs_failure,		what		)
 		    __field(size_t,			len		)
-		    __field(size_t,			transferred	)
+		    __field(size_t,			remain		)
 		    __field(loff_t,			start		)
 			     ),
 
@@ -242,7 +242,7 @@  TRACE_EVENT(netfs_failure,
 		    __entry->source	= sreq ? sreq->source : NETFS_INVALID_READ;
 		    __entry->what	= what;
 		    __entry->len	= sreq ? sreq->len : 0;
-		    __entry->transferred = sreq ? sreq->transferred : 0;
+		    __entry->remain	= sreq ? iov_iter_count(&sreq->iter) : 0;
 		    __entry->start	= sreq ? sreq->start : 0;
 			   ),
 
@@ -250,7 +250,7 @@  TRACE_EVENT(netfs_failure,
 		      __entry->rreq, __entry->index,
 		      __print_symbolic(__entry->source, netfs_sreq_sources),
 		      __entry->flags,
-		      __entry->start, __entry->transferred, __entry->len,
+		      __entry->start, __entry->len - __entry->remain, __entry->len,
 		      __print_symbolic(__entry->what, netfs_failures),
 		      __entry->error)
 	    );