[PATCH] netfs: Set NETFS_RREQ_WRITE_TO_CACHE when caching is possible

[Hristo Venev <hristo@venev.name>]

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In addition to Ceph, in NFS there are also some crashes related to the
use of 0x356 as a pointer.

`netfs_is_cache_enabled()` only returns true when the fscache cookie is
fully initialized. This may happen after the request has been created,
so check for the cookie's existence instead.

Link: https://lore.kernel.org/linux-nfs/b78c88db-8b3a-4008-94cb-82ae08f0e37b@free.fr/T/
Fixes: 2ff1e97587f4 ("netfs: Replace PG_fscache by setting folio->private and marking dirty")
Cc: linux-nfs@vger.kernel.org <linux-nfs@vger.kernel.org>
Cc: blokos <blokos@free.fr>
Cc: Trond Myklebust <trondmy@hammerspace.com>
Cc: dan.aloni@vastdata.com <dan.aloni@vastdata.com>
Signed-off-by: Hristo Venev <hristo@venev.name>
---
 fs/netfs/objects.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/fs/netfs/objects.c b/fs/netfs/objects.c
index f4a6427274792..a74ca90c86c9b 100644
--- a/fs/netfs/objects.c
+++ b/fs/netfs/objects.c
@@ -27,7 +27,6 @@ struct netfs_io_request *netfs_alloc_request(struct address_space *mapping,
 	bool is_unbuffered = (origin == NETFS_UNBUFFERED_WRITE ||
 			      origin == NETFS_DIO_READ ||
 			      origin == NETFS_DIO_WRITE);
-	bool cached = !is_unbuffered && netfs_is_cache_enabled(ctx);
 	int ret;
 
 	for (;;) {
@@ -56,8 +55,9 @@ struct netfs_io_request *netfs_alloc_request(struct address_space *mapping,
 	refcount_set(&rreq->ref, 1);
 
 	__set_bit(NETFS_RREQ_IN_PROGRESS, &rreq->flags);
-	if (cached) {
-		__set_bit(NETFS_RREQ_WRITE_TO_CACHE, &rreq->flags);
+	if (!is_unbuffered && fscache_cookie_valid(netfs_i_cookie(ctx))) {
+		if(netfs_is_cache_enabled(ctx))
+			__set_bit(NETFS_RREQ_WRITE_TO_CACHE, &rreq->flags);
 		if (test_bit(NETFS_ICTX_USE_PGPRIV2, &ctx->flags))
 			/* Filesystem uses deprecated PG_private_2 marking. */
 			__set_bit(NETFS_RREQ_USE_PGPRIV2, &rreq->flags);


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