fuse: add helper for asynchronous writes

This patch adds a new helper function fuse_write_fill() which makes it
possible to send WRITE requests asynchronously.

A new flag for WRITE requests is also added which indicates that this a write
from the page cache, and not a "normal" file write.

This patch is in preparation for writable mmap support.

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

3 files changed, 31 insertions, 13 deletions

diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index c4c59c7d0038..2b589de044e8 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -443,30 +443,37 @@ out:
         return err;
 }
 
-static size_t fuse_send_write(struct fuse_req *req, struct file *file,
-                              struct inode *inode, loff_t pos, size_t count)
+static void fuse_write_fill(struct fuse_req *req, struct fuse_file *ff,
+                            struct inode *inode, loff_t pos, size_t count,
+                            int writepage)
 {
-        struct fuse_conn *fc = get_fuse_conn(inode);
-        struct fuse_file *ff = file->private_data;
-        struct fuse_write_in inarg;
-        struct fuse_write_out outarg;
+        struct fuse_write_in *inarg = &req->misc.write.in;
+        struct fuse_write_out *outarg = &req->misc.write.out;
 
-        memset(&inarg, 0, sizeof(struct fuse_write_in));
-        inarg.fh = ff->fh;
-        inarg.offset = pos;
-        inarg.size = count;
+        memset(inarg, 0, sizeof(struct fuse_write_in));
+        inarg->fh = ff->fh;
+        inarg->offset = pos;
+        inarg->size = count;
+        inarg->write_flags = writepage ? FUSE_WRITE_CACHE : 0;
         req->in.h.opcode = FUSE_WRITE;
         req->in.h.nodeid = get_node_id(inode);
         req->in.argpages = 1;
         req->in.numargs = 2;
         req->in.args[0].size = sizeof(struct fuse_write_in);
-        req->in.args[0].value = &inarg;
+        req->in.args[0].value = inarg;
         req->in.args[1].size = count;
         req->out.numargs = 1;
         req->out.args[0].size = sizeof(struct fuse_write_out);
-        req->out.args[0].value = &outarg;
+        req->out.args[0].value = outarg;
+}
+
+static size_t fuse_send_write(struct fuse_req *req, struct file *file,
+                              struct inode *inode, loff_t pos, size_t count)
+{
+        struct fuse_conn *fc = get_fuse_conn(inode);
+        fuse_write_fill(req, file->private_data, inode, pos, count, 0);
         request_send(fc, req);
-        return outarg.size;
+        return req->misc.write.out.size;
 }
 
 static int fuse_write_begin(struct file *file, struct address_space *mapping,
diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index 5657cca0d0cb..8b64a630e758 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -219,6 +219,10 @@ struct fuse_req {
                 struct fuse_init_in init_in;
                 struct fuse_init_out init_out;
                 struct fuse_read_in read_in;
+                struct {
+                        struct fuse_write_in in;
+                        struct fuse_write_out out;
+                } write;
                 struct fuse_lk_in lk_in;
         } misc;
 
diff --git a/include/linux/fuse.h b/include/linux/fuse.h
index 015a8b15a388..6f4a31266cd5 100644
--- a/include/linux/fuse.h
+++ b/include/linux/fuse.h
@@ -119,6 +119,13 @@ struct fuse_file_lock {
  */
 #define FUSE_LK_FLOCK           (1 << 0)
 
+/**
+ * WRITE flags
+ *
+ * FUSE_WRITE_CACHE: delayed write from page cache, file handle is guessed
+ */
+#define FUSE_WRITE_CACHE        (1 << 0)
+
 enum fuse_opcode {
         FUSE_LOOKUP        = 1,
         FUSE_FORGET        = 2,  /* no reply */