[PATCH] netfs: Set NETFS_RREQ_WRITE_TO_CACHE when caching is possible

From: Hristo Venev
Date: Sun Aug 04 2024 - 09:58:38 EST


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@xxxxxxx/T/
Fixes: 2ff1e97587f4 ("netfs: Replace PG_fscache by setting folio->private and marking dirty")
Cc: linux-nfs@xxxxxxxxxxxxxxx <linux-nfs@xxxxxxxxxxxxxxx>
Cc: blokos <blokos@xxxxxxx>
Cc: Trond Myklebust <trondmy@xxxxxxxxxxxxxxx>
Cc: dan.aloni@xxxxxxxxxxxx <dan.aloni@xxxxxxxxxxxx>
Signed-off-by: Hristo Venev <hristo@xxxxxxxxxx>
---
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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