fuse: serialize dirops by default

Negotiate with userspace filesystems whether they support parallel readdir
and lookup.  Disable parallelism by default for fear of breaking fuse
filesystems.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Fixes: 9902af79c01a ("parallel lookups: actual switch to rwsem")
Fixes: d9b3dbdcfd62 ("fuse: switch to ->iterate_shared()")

1 files changed, 9 insertions, 0 deletions

diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index eddbe02c4028..929c383432b0 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -110,6 +110,9 @@ struct fuse_inode {
 
         /** Miscellaneous bits describing inode state */
         unsigned long state;
+
+        /** Lock for serializing lookup and readdir for back compatibility*/
+        struct mutex mutex;
 };
 
 /** FUSE inode state bits */
@@ -540,6 +543,9 @@ struct fuse_conn {
         /** write-back cache policy (default is write-through) */
         unsigned writeback_cache:1;
 
+        /** allow parallel lookups and readdir (default is serialized) */
+        unsigned parallel_dirops:1;
+
         /*
          * The following bitfields are only for optimization purposes
          * and hence races in setting them will not cause malfunction
@@ -956,4 +962,7 @@ int fuse_do_setattr(struct inode *inode, struct iattr *attr,
 
 void fuse_set_initialized(struct fuse_conn *fc);
 
+void fuse_unlock_inode(struct inode *inode);
+void fuse_lock_inode(struct inode *inode);
+
 #endif /* _FS_FUSE_I_H */