fuse: add atomic open+truncate support

This patch allows fuse filesystems to implement open(..., O_TRUNC) as a single
request, instead of separate truncate and open requests.

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>

1 files changed, 4 insertions, 1 deletions

diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
index 6ef3973f4048..3c13981f48e2 100644
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -531,6 +531,8 @@ static void process_init_reply(struct fuse_conn *fc, struct fuse_req *req)
                                 fc->async_read = 1;
                         if (!(arg->flags & FUSE_POSIX_LOCKS))
                                 fc->no_lock = 1;
+                        if (arg->flags & FUSE_ATOMIC_O_TRUNC)
+                                fc->atomic_o_trunc = 1;
                 } else {
                         ra_pages = fc->max_read / PAGE_CACHE_SIZE;
                         fc->no_lock = 1;
@@ -553,7 +555,8 @@ static void fuse_send_init(struct fuse_conn *fc, struct fuse_req *req)
         arg->major = FUSE_KERNEL_VERSION;
         arg->minor = FUSE_KERNEL_MINOR_VERSION;
         arg->max_readahead = fc->bdi.ra_pages * PAGE_CACHE_SIZE;
-        arg->flags |= FUSE_ASYNC_READ | FUSE_POSIX_LOCKS | FUSE_FILE_OPS;
+        arg->flags |= FUSE_ASYNC_READ | FUSE_POSIX_LOCKS | FUSE_FILE_OPS |
+                FUSE_ATOMIC_O_TRUNC;
         req->in.h.opcode = FUSE_INIT;
         req->in.numargs = 1;
         req->in.args[0].size = sizeof(*arg);