fuse: add flag to turn on async direct IO

Without async DIO write requests to a single file were always serialized.
With async DIO that's no longer the case.

So don't turn on async DIO by default for fear of breaking backward
compatibility.

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

3 files changed, 10 insertions, 5 deletions

diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index 1f8e3d60dc07..6ab7ca43f9e0 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -2371,14 +2371,14 @@ fuse_direct_IO(int rw, struct kiocb *iocb, const struct iovec *iov,
                         loff_t offset, unsigned long nr_segs)
 {
         ssize_t ret = 0;
-        struct file *file = NULL;
+        struct file *file = iocb->ki_filp;
+        struct fuse_file *ff = file->private_data;
         loff_t pos = 0;
         struct inode *inode;
         loff_t i_size;
         size_t count = iov_length(iov, nr_segs);
         struct fuse_io_priv *io;
 
-        file = iocb->ki_filp;
         pos = offset;
         inode = file->f_mapping->host;
         i_size = i_size_read(inode);
@@ -2403,9 +2403,9 @@ fuse_direct_IO(int rw, struct kiocb *iocb, const struct iovec *iov,
         io->file = file;
         /*
          * By default, we want to optimize all I/Os with async request
-         * submission to the client filesystem.
+         * submission to the client filesystem if supported.
          */
-        io->async = 1;
+        io->async = ff->fc->async_dio;
         io->iocb = iocb;
 
         /*
diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index 53b830e3b38f..fde7249a3a96 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -541,6 +541,9 @@ struct fuse_conn {
         /** Does the filesystem want adaptive readdirplus? */
         unsigned readdirplus_auto:1;
 
+        /** Does the filesystem support asynchronous direct-IO submission? */
+        unsigned async_dio:1;
+
         /** The number of requests waiting for completion */
         atomic_t num_waiting;
 
diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
index 17ec1f70524d..6201f81e4d3a 100644
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -871,6 +871,8 @@ static void process_init_reply(struct fuse_conn *fc, struct fuse_req *req)
                                 fc->do_readdirplus = 1;
                         if (arg->flags & FUSE_READDIRPLUS_AUTO)
                                 fc->readdirplus_auto = 1;
+                        if (arg->flags & FUSE_ASYNC_DIO)
+                                fc->async_dio = 1;
                 } else {
                         ra_pages = fc->max_read / PAGE_CACHE_SIZE;
                         fc->no_lock = 1;
@@ -898,7 +900,7 @@ static void fuse_send_init(struct fuse_conn *fc, struct fuse_req *req)
                 FUSE_EXPORT_SUPPORT | FUSE_BIG_WRITES | FUSE_DONT_MASK |
                 FUSE_SPLICE_WRITE | FUSE_SPLICE_MOVE | FUSE_SPLICE_READ |
                 FUSE_FLOCK_LOCKS | FUSE_IOCTL_DIR | FUSE_AUTO_INVAL_DATA |
-                FUSE_DO_READDIRPLUS | FUSE_READDIRPLUS_AUTO;
+                FUSE_DO_READDIRPLUS | FUSE_READDIRPLUS_AUTO | FUSE_ASYNC_DIO;
         req->in.h.opcode = FUSE_INIT;
         req->in.numargs = 1;
         req->in.args[0].size = sizeof(*arg);