anonfd: Allow making anon files read-only

It seems a couple places such as arch/ia64/kernel/perfmon.c and
drivers/infiniband/core/uverbs_main.c could use anon_inode_getfile()
instead of a private pseudo-fs + alloc_file(), if only there were a way
to get a read-only file.  So provide this by having anon_inode_getfile()
create a read-only file if we pass O_RDONLY in flags.

Signed-off-by: Roland Dreier <rolandd@cisco.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 1 insertions, 1 deletions

diff --git a/kernel/perf_event.c b/kernel/perf_event.c
index e0eb4a2fe183..1f38270f08c7 100644
--- a/kernel/perf_event.c
+++ b/kernel/perf_event.c
@@ -4724,7 +4724,7 @@ SYSCALL_DEFINE5(perf_event_open,
         if (IS_ERR(event))
                 goto err_put_context;
 
-        err = anon_inode_getfd("[perf_event]", &perf_fops, event, 0);
+        err = anon_inode_getfd("[perf_event]", &perf_fops, event, O_RDWR);
         if (err < 0)
                 goto err_free_put_context;