[PATCH 9/10] fuse: Turn writeback on

[Pavel Emelyanov <xemul-bzQdu9zFT3WakBO8gow8eQ@public.gmane.org>]

Introduce a bit kernel and userspace exchange between each-other on
the init stage and turn writeback on if the userspace want this.

Also add each writable file into per-inode write list and call the
generic_file_aio_write to make use of the Linux page cache engine.

Signed-off-by: Pavel Emelyanov <xemul-GEFAQzZX7r8dnm+yROfE0A@public.gmane.org>
---
 fs/fuse/file.c       |    5 +++++
 fs/fuse/inode.c      |    4 +++-
 include/linux/fuse.h |    1 +
 3 files changed, 9 insertions(+), 1 deletions(-)

diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index 058498d..e3a1cc8 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -209,6 +209,8 @@ void fuse_finish_open(struct inode *inode, struct file *file)
 		spin_unlock(&fc->lock);
 		fuse_invalidate_attr(inode);
 	}
+	if ((file->f_mode & FMODE_WRITE) && fc->writeback_cache)
+		fuse_link_write_file(file);
 }
 
 int fuse_open_common(struct inode *inode, struct file *file, bool isdir)
@@ -999,6 +1001,9 @@ static ssize_t fuse_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
 	struct iov_iter i;
 	loff_t endbyte = 0;
 
+	if (get_fuse_conn(inode)->writeback_cache)
+		return generic_file_aio_write(iocb, iov, nr_segs, pos);
+
 	WARN_ON(iocb->ki_pos != pos);
 
 	ocount = 0;
diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
index 88c577f..df1dc83 100644
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -836,6 +836,8 @@ static void process_init_reply(struct fuse_conn *fc, struct fuse_req *req)
 				fc->big_writes = 1;
 			if (arg->flags & FUSE_DONT_MASK)
 				fc->dont_mask = 1;
+			if (arg->flags & FUSE_WRITEBACK_CACHE)
+				fc->writeback_cache = 1;
 		} else {
 			ra_pages = fc->max_read / PAGE_CACHE_SIZE;
 			fc->no_lock = 1;
@@ -861,7 +863,7 @@ static void fuse_send_init(struct fuse_conn *fc, struct fuse_req *req)
 	arg->max_readahead = fc->bdi.ra_pages * PAGE_CACHE_SIZE;
 	arg->flags |= FUSE_ASYNC_READ | FUSE_POSIX_LOCKS | FUSE_ATOMIC_O_TRUNC |
 		FUSE_EXPORT_SUPPORT | FUSE_BIG_WRITES | FUSE_DONT_MASK |
-		FUSE_FLOCK_LOCKS;
+		FUSE_FLOCK_LOCKS | FUSE_WRITEBACK_CACHE;
 	req->in.h.opcode = FUSE_INIT;
 	req->in.numargs = 1;
 	req->in.args[0].size = sizeof(*arg);
diff --git a/include/linux/fuse.h b/include/linux/fuse.h
index 9303348..7ed5ced 100644
--- a/include/linux/fuse.h
+++ b/include/linux/fuse.h
@@ -176,6 +176,7 @@ struct fuse_file_lock {
 #define FUSE_BIG_WRITES		(1 << 5)
 #define FUSE_DONT_MASK		(1 << 6)
 #define FUSE_FLOCK_LOCKS	(1 << 10)
+#define FUSE_WRITEBACK_CACHE	(1 << 11)
 
 /**
  * CUSE INIT request/reply flags
-- 
1.5.5.6

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