fuse: fix LOOKUP vs INIT compat handling

Analysis from Marc:

 "Commit 7078187a795f ("fuse: introduce fuse_simple_request() helper")
  from the above pull request triggers some EIO errors for me in some tests
  that rely on fuse

  Looking at the code changes and a bit of debugging info I think there's a
  general problem here that fuse_get_req checks and possibly waits for
  fc->initialized, and this was always called first.  But this commit
  changes the ordering and in many places fc->minor is now possibly used
  before fuse_get_req, and we can't be sure that fc has been initialized.
  In my case fuse_lookup_init sets req->out.args[0].size to the wrong size
  because fc->minor at that point is still 0, leading to the EIO error."

Fix by moving the compat adjustments into fuse_simple_request() to after
fuse_get_req().

This is also more readable than the original, since now compatibility is
handled in a single function instead of cluttering each operation.

Reported-by: Marc Dionne <marc.c.dionne@gmail.com>
Tested-by: Marc Dionne <marc.c.dionne@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Fixes: 7078187a795f ("fuse: introduce fuse_simple_request() helper")

1 files changed, 1 insertions, 2 deletions

diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
index 6749109f255d..6a20f2ff2c2e 100644
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -424,8 +424,7 @@ static int fuse_statfs(struct dentry *dentry, struct kstatfs *buf)
 	args.in.h.opcode = FUSE_STATFS;
 	args.in.h.nodeid = get_node_id(dentry->d_inode);
 	args.out.numargs = 1;
-	args.out.args[0].size =
-		fc->minor < 4 ? FUSE_COMPAT_STATFS_SIZE : sizeof(outarg);
+	args.out.args[0].size = sizeof(outarg);
 	args.out.args[0].value = &outarg;
 	err = fuse_simple_request(fc, &args);
 	if (!err)