Merge patch series "netfs: Fix use of fscache with ceph"

David Howells <dhowells@redhat.com> says:

Here are a couple of patches that fix the use of fscaching with ceph:

 (1) Fix the read collector to mark the write request that it creates to copy
     data to the cache with NETFS_RREQ_OFFLOAD_COLLECTION so that it will run
     the write collector on a workqueue as it's meant to run in the background
     and the app isn't going to wait for it.

 (2) Fix the read collector to wake up the copy-to-cache write request after
     it sets NETFS_RREQ_ALL_QUEUED if the write request doesn't have any
     subrequests left on it.  ALL_QUEUED indicates that there won't be any
     more subreqs coming and the collector should clean up - except that an
     event is needed to trigger that, but it only gets events from subreq
     termination and so the last event can beat us to setting ALL_QUEUED.

* patches from https://lore.kernel.org/20250711151005.2956810-1-dhowells@redhat.com:
  netfs: Fix race between cache write completion and ALL_QUEUED being set
  netfs: Fix copy-to-cache so that it performs collection with ceph+fscache

Link: https://lore.kernel.org/20250711151005.2956810-1-dhowells@redhat.com
Signed-off-by: Christian Brauner <brauner@kernel.org>

2 files changed, 35 insertions, 0 deletions

diff --git a/fs/netfs/read_pgpriv2.c b/fs/netfs/read_pgpriv2.c
index 5bbe906a551d..8097bc069c1d 100644
--- a/fs/netfs/read_pgpriv2.c
+++ b/fs/netfs/read_pgpriv2.c
@@ -110,6 +110,8 @@ static struct netfs_io_request *netfs_pgpriv2_begin_copy_to_cache(
 	if (!creq->io_streams[1].avail)
 		goto cancel_put;
 
+	__set_bit(NETFS_RREQ_OFFLOAD_COLLECTION, &creq->flags);
+	trace_netfs_copy2cache(rreq, creq);
 	trace_netfs_write(creq, netfs_write_trace_copy_to_cache);
 	netfs_stat(&netfs_n_wh_copy_to_cache);
 	rreq->copy_to_cache = creq;
@@ -154,6 +156,9 @@ void netfs_pgpriv2_end_copy_to_cache(struct netfs_io_request *rreq)
 	netfs_issue_write(creq, &creq->io_streams[1]);
 	smp_wmb(); /* Write lists before ALL_QUEUED. */
 	set_bit(NETFS_RREQ_ALL_QUEUED, &creq->flags);
+	trace_netfs_rreq(rreq, netfs_rreq_trace_end_copy_to_cache);
+	if (list_empty_careful(&creq->io_streams[1].subrequests))
+		netfs_wake_collector(creq);
 
 	netfs_put_request(creq, netfs_rreq_trace_put_return);
 	creq->copy_to_cache = NULL;
diff --git a/include/trace/events/netfs.h b/include/trace/events/netfs.h
index 73e96ccbe830..64a382fbc31a 100644
--- a/include/trace/events/netfs.h
+++ b/include/trace/events/netfs.h
@@ -55,6 +55,7 @@
 	EM(netfs_rreq_trace_copy,		"COPY   ")	\
 	EM(netfs_rreq_trace_dirty,		"DIRTY  ")	\
 	EM(netfs_rreq_trace_done,		"DONE   ")	\
+	EM(netfs_rreq_trace_end_copy_to_cache,	"END-C2C")	\
 	EM(netfs_rreq_trace_free,		"FREE   ")	\
 	EM(netfs_rreq_trace_ki_complete,	"KI-CMPL")	\
 	EM(netfs_rreq_trace_recollect,		"RECLLCT")	\
@@ -559,6 +560,35 @@ TRACE_EVENT(netfs_write,
 		      __entry->start, __entry->start + __entry->len - 1)
 	    );
 
+TRACE_EVENT(netfs_copy2cache,
+	    TP_PROTO(const struct netfs_io_request *rreq,
+		     const struct netfs_io_request *creq),
+
+	    TP_ARGS(rreq, creq),
+
+	    TP_STRUCT__entry(
+		    __field(unsigned int,		rreq)
+		    __field(unsigned int,		creq)
+		    __field(unsigned int,		cookie)
+		    __field(unsigned int,		ino)
+			     ),
+
+	    TP_fast_assign(
+		    struct netfs_inode *__ctx = netfs_inode(rreq->inode);
+		    struct fscache_cookie *__cookie = netfs_i_cookie(__ctx);
+		    __entry->rreq	= rreq->debug_id;
+		    __entry->creq	= creq->debug_id;
+		    __entry->cookie	= __cookie ? __cookie->debug_id : 0;
+		    __entry->ino	= rreq->inode->i_ino;
+			   ),
+
+	    TP_printk("R=%08x CR=%08x c=%08x i=%x ",
+		      __entry->rreq,
+		      __entry->creq,
+		      __entry->cookie,
+		      __entry->ino)
+	    );
+
 TRACE_EVENT(netfs_collect,
 	    TP_PROTO(const struct netfs_io_request *wreq),