fuse: add memory barrier to INIT

Theoretically we need to order setting of various fields in fc with
fc->initialized.

No known bug reports related to this yet.

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>

3 files changed, 16 insertions, 3 deletions

diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
index c847d6b225e2..ed19a7d622fa 100644
--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -131,6 +131,13 @@ static void fuse_req_init_context(struct fuse_req *req)
         req->in.h.pid = current->pid;
 }
 
+void fuse_set_initialized(struct fuse_conn *fc)
+{
+        /* Make sure stores before this are seen on another CPU */
+        smp_wmb();
+        fc->initialized = 1;
+}
+
 static bool fuse_block_alloc(struct fuse_conn *fc, bool for_background)
 {
         return !fc->initialized || (for_background && fc->blocked);
@@ -155,6 +162,8 @@ static struct fuse_req *__fuse_get_req(struct fuse_conn *fc, unsigned npages,
                 if (intr)
                         goto out;
         }
+        /* Matches smp_wmb() in fuse_set_initialized() */
+        smp_rmb();
 
         err = -ENOTCONN;
         if (!fc->connected)
@@ -253,6 +262,8 @@ struct fuse_req *fuse_get_req_nofail_nopages(struct fuse_conn *fc,
 
         atomic_inc(&fc->num_waiting);
         wait_event(fc->blocked_waitq, fc->initialized);
+        /* Matches smp_wmb() in fuse_set_initialized() */
+        smp_rmb();
         req = fuse_request_alloc(0);
         if (!req)
                 req = get_reserved_req(fc, file);
@@ -2163,7 +2174,7 @@ void fuse_abort_conn(struct fuse_conn *fc)
         if (fc->connected) {
                 fc->connected = 0;
                 fc->blocked = 0;
-                fc->initialized = 1;
+                fuse_set_initialized(fc);
                 end_io_requests(fc);
                 end_queued_requests(fc);
                 end_polls(fc);
@@ -2182,7 +2193,7 @@ int fuse_dev_release(struct inode *inode, struct file *file)
                 spin_lock(&fc->lock);
                 fc->connected = 0;
                 fc->blocked = 0;
-                fc->initialized = 1;
+                fuse_set_initialized(fc);
                 end_queued_requests(fc);
                 end_polls(fc);
                 wake_up_all(&fc->blocked_waitq);
diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index e0fc6725d1d0..1cdfb07c1376 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -906,4 +906,6 @@ int fuse_write_inode(struct inode *inode, struct writeback_control *wbc);
 int fuse_do_setattr(struct inode *inode, struct iattr *attr,
                     struct file *file);
 
+void fuse_set_initialized(struct fuse_conn *fc);
+
 #endif /* _FS_FUSE_I_H */
diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
index 6a20f2ff2c2e..f38256e4476e 100644
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -897,7 +897,7 @@ static void process_init_reply(struct fuse_conn *fc, struct fuse_req *req)
                 fc->max_write = max_t(unsigned, 4096, fc->max_write);
                 fc->conn_init = 1;
         }
-        fc->initialized = 1;
+        fuse_set_initialized(fc);
         wake_up_all(&fc->blocked_waitq);
 }