[PATCH] fuse: add POSIX file locking support

This patch adds POSIX file locking support to the fuse interface.

This implementation doesn't keep any locking state in kernel.  Unlocking on
close() is handled by the FLUSH message, which now contains the lock owner id.

Mandatory locking is not supported.  The filesystem may enfoce mandatory
locking in userspace if needed.

Signed-off-by: Miklos Szeredi <miklos@szeredi.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 18 insertions, 2 deletions

diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
index 13a7e8ab7a78..412892905838 100644
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -98,6 +98,14 @@ static void fuse_clear_inode(struct inode *inode)
         }
 }
 
+static int fuse_remount_fs(struct super_block *sb, int *flags, char *data)
+{
+        if (*flags & MS_MANDLOCK)
+                return -EINVAL;
+
+        return 0;
+}
+
 void fuse_change_attributes(struct inode *inode, struct fuse_attr *attr)
 {
         if (S_ISREG(inode->i_mode) && i_size_read(inode) != attr->size)
@@ -409,6 +417,7 @@ static struct super_operations fuse_super_operations = {
         .destroy_inode  = fuse_destroy_inode,
         .read_inode     = fuse_read_inode,
         .clear_inode    = fuse_clear_inode,
+        .remount_fs     = fuse_remount_fs,
         .put_super      = fuse_put_super,
         .umount_begin   = fuse_umount_begin,
         .statfs         = fuse_statfs,
@@ -428,8 +437,12 @@ static void process_init_reply(struct fuse_conn *fc, struct fuse_req *req)
                         ra_pages = arg->max_readahead / PAGE_CACHE_SIZE;
                         if (arg->flags & FUSE_ASYNC_READ)
                                 fc->async_read = 1;
-                } else
+                        if (!(arg->flags & FUSE_POSIX_LOCKS))
+                                fc->no_lock = 1;
+                } else {
                         ra_pages = fc->max_read / PAGE_CACHE_SIZE;
+                        fc->no_lock = 1;
+                }
 
                 fc->bdi.ra_pages = min(fc->bdi.ra_pages, ra_pages);
                 fc->minor = arg->minor;
@@ -447,7 +460,7 @@ 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;
+        arg->flags |= FUSE_ASYNC_READ | FUSE_POSIX_LOCKS;
         req->in.h.opcode = FUSE_INIT;
         req->in.numargs = 1;
         req->in.args[0].size = sizeof(*arg);
@@ -479,6 +492,9 @@ static int fuse_fill_super(struct super_block *sb, void *data, int silent)
         struct fuse_req *init_req;
         int err;
 
+        if (sb->s_flags & MS_MANDLOCK)
+                return -EINVAL;
+
         if (!parse_fuse_opt((char *) data, &d))
                 return -EINVAL;