fuse: fix max i/o size calculation

Fix a bug that Werner Baumann reported: fuse can send a bigger write request
than the maximum specified.  This only affected direct_io operation.

In addition set a sane minimum for the max_read and max_write tunables, so I/O
always makes some progress.

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, 2 insertions, 1 deletions

diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
index 7d01c68852a8..0cef5ea319f3 100644
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -584,6 +584,7 @@ static void process_init_reply(struct fuse_conn *fc, struct fuse_req *req)
                 fc->bdi.ra_pages = min(fc->bdi.ra_pages, ra_pages);
                 fc->minor = arg->minor;
                 fc->max_write = arg->minor < 5 ? 4096 : arg->max_write;
+                fc->max_write = min_t(unsigned, 4096, fc->max_write);
                 fc->conn_init = 1;
         }
         fuse_put_request(fc, req);
@@ -658,7 +659,7 @@ static int fuse_fill_super(struct super_block *sb, void *data, int silent)
         fc->flags = d.flags;
         fc->user_id = d.user_id;
         fc->group_id = d.group_id;
-        fc->max_read = d.max_read;
+        fc->max_read = min_t(unsigned, 4096, d.max_read);
 
         /* Used by get_root_inode() */
         sb->s_fs_info = fc;