[PATCH] netfs: Fix barriering when walking subrequest list
David Howells <[email protected]> Thu, 02 Jul 2026 09:23:02 +0100
| Newsgroups | dev.linux.lists.netfs,org.kernel.vger.linux-fsdevel,org.kernel.vger.linux-kernel |
|---|---|
| Organization | Red Hat UK Ltd. Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SI4 1TE, United Kingdom. Registered in England and Wales under Company Registration No. 3798903 |
| Message-ID | <[email protected]> |
Fix the barriering used when walking the subrequest list in retry as
there's a possibility of seeing a subreq that's just been added by the
application thread.
Fixes: ee4cdf7ba857 ("netfs: Speed up buffered reading")
Fixes: 288ace2f57c9 ("netfs: New writeback implementation")
Link: https://sashiko.dev/#/patchset/20260608145432.681865-1-dhowells%40redhat.com
Signed-off-by: David Howells <[email protected]>
cc: Paulo Alcantara <[email protected]>
cc: [email protected]
cc: [email protected]
---
fs/netfs/read_retry.c | 7 ++++++-
fs/netfs/write_retry.c | 7 ++++++-
2 files changed, 12 insertions(+), 2 deletions(-)
diff --git a/fs/netfs/read_retry.c b/fs/netfs/read_retry.c
index f59a70f3a086..2b42758e01ec 100644
--- a/fs/netfs/read_retry.c
+++ b/fs/netfs/read_retry.c
@@ -98,7 +98,12 @@ static void netfs_retry_read_subrequests(struct netfs_io_request *rreq)
goto abandon;
}
- list_for_each_continue(next, &stream->subrequests) {
+ for (;;) {
+ /* Read pointer to subreq before reading subreq state. */
+ next = smp_load_acquire(&next->next);
+ if (next == &stream->subrequests)
+ break;
+
subreq = list_entry(next, struct netfs_io_subrequest, rreq_link);
if (subreq->start + subreq->transferred != start + len ||
test_bit(NETFS_SREQ_BOUNDARY, &subreq->flags) ||
diff --git a/fs/netfs/write_retry.c b/fs/netfs/write_retry.c
index 32735abfa03f..058bc7a166a5 100644
--- a/fs/netfs/write_retry.c
+++ b/fs/netfs/write_retry.c
@@ -72,7 +72,12 @@ static void netfs_retry_write_stream(struct netfs_io_request *wreq,
!test_bit(NETFS_SREQ_NEED_RETRY, &from->flags))
return;
- list_for_each_continue(next, &stream->subrequests) {
+ for (;;) {
+ /* Read pointer to subreq before reading subreq state. */
+ next = smp_load_acquire(&next->next);
+ if (next == &stream->subrequests)
+ break;
+
subreq = list_entry(next, struct netfs_io_subrequest, rreq_link);
if (subreq->start + subreq->transferred != start + len ||
test_bit(NETFS_SREQ_BOUNDARY, &subreq->flags) ||