fuse: enable asynchronous processing direct IO

In case of synchronous DIO request (i.e. read(2) or write(2) for a file
opened with O_DIRECT), the patch submits fuse requests asynchronously, but
waits for their completions before return from fuse_direct_IO().

In case of asynchronous DIO request (i.e. libaio io_submit() or a file opened
with O_DIRECT), the patch submits fuse requests asynchronously and return
-EIOCBQUEUED immediately.

The only special case is async DIO extending file. Here the patch falls back
to old behaviour because we can't return -EIOCBQUEUED and update i_size later,
without i_mutex hold. And we have no method to wait on real async I/O
requests.

The patch also clean __fuse_direct_write() up: it's better to update i_size
in its callers. Thanks Brian for suggestion.

Signed-off-by: Maxim Patlasov <mpatlasov@parallels.com>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>

diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index e207dcd..ba1d503 100644 (file)
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -1366,11 +1366,8 @@ static ssize_t __fuse_direct_write(struct fuse_io_priv *io,
        ssize_t res;
 
        res = generic_write_checks(file, ppos, &count, 0);
-       if (!res) {
+       if (!res)
                res = fuse_direct_io(io, iov, nr_segs, count, ppos, 1);
-               if (!io->async && res > 0)
-                       fuse_write_update_size(inode, *ppos);
-       }
 
        fuse_invalidate_attr(inode);
 
@@ -1391,6 +1388,8 @@ static ssize_t fuse_direct_write(struct file *file, const char __user *buf,
        /* Don't allow parallel writes to the same file */
        mutex_lock(&inode->i_mutex);
        res = __fuse_direct_write(&io, &iov, 1, ppos);
+       if (res > 0)
+               fuse_write_update_size(inode, *ppos);
        mutex_unlock(&inode->i_mutex);
 
        return res;
@@ -2360,23 +2359,61 @@ fuse_direct_IO(int rw, struct kiocb *iocb, const struct iovec *iov,
        ssize_t ret = 0;
        struct file *file = NULL;
        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);
 
-       io = kzalloc(sizeof(struct fuse_io_priv), GFP_KERNEL);
+       io = kmalloc(sizeof(struct fuse_io_priv), GFP_KERNEL);
        if (!io)
                return -ENOMEM;
-
+       spin_lock_init(&io->lock);
+       io->reqs = 1;
+       io->bytes = -1;
+       io->size = 0;
+       io->offset = offset;
+       io->write = (rw == WRITE);
+       io->err = 0;
        io->file = file;
+       /*
+        * By default, we want to optimize all I/Os with async request
+        * submission to the client filesystem.
+        */
+       io->async = 1;
+       io->iocb = iocb;
+
+       /*
+        * We cannot asynchronously extend the size of a file. We have no method
+        * to wait on real async I/O requests, so we must submit this request
+        * synchronously.
+        */
+       if (!is_sync_kiocb(iocb) && (offset + count > i_size) && rw == WRITE)
+               io->async = false;
 
        if (rw == WRITE)
                ret = __fuse_direct_write(io, iov, nr_segs, &pos);
        else
                ret = __fuse_direct_read(io, iov, nr_segs, &pos);
 
-       kfree(io);
+       if (io->async) {
+               fuse_aio_complete(io, ret < 0 ? ret : 0, -1);
+
+               /* we have a non-extending, async request, so return */
+               if (ret > 0 && !is_sync_kiocb(iocb))
+                       return -EIOCBQUEUED;
+
+               ret = wait_on_sync_kiocb(iocb);
+       } else {
+               kfree(io);
+       }
+
+       if (rw == WRITE && ret > 0)
+               fuse_write_update_size(inode, pos);
 
        return ret;
 }