If multiple subrequests donate data to the same "next" request (depending on the subrequest completion order), each of them would overwrite the `prev_donated` field, causing data corruption and a BUG() crash ("Can't donate prior to front").
Fixes: ee4cdf7ba857 ("netfs: Speed up buffered reading") Closes: https://lore.kernel.org/netfs/CAKPOu+_4mUwYgQtRTbXCmi+-k3PGvLysnPadkmHOyB7Gz... Cc: stable@vger.kernel.org Signed-off-by: Max Kellermann max.kellermann@ionos.com Signed-off-by: David Howells dhowells@redhat.com --- fs/netfs/read_collect.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/fs/netfs/read_collect.c b/fs/netfs/read_collect.c index 8878b46589ff..cafadfe8e858 100644 --- a/fs/netfs/read_collect.c +++ b/fs/netfs/read_collect.c @@ -284,7 +284,7 @@ static bool netfs_consume_read_data(struct netfs_io_subrequest *subreq, bool was netfs_trace_donate_to_deferred_next); } else { next = list_next_entry(subreq, rreq_link); - WRITE_ONCE(next->prev_donated, excess); + WRITE_ONCE(next->prev_donated, next->prev_donated + excess); trace_netfs_donate(rreq, subreq, next, excess, netfs_trace_donate_to_next); }