[fuse-devel] Problem with release coming after unlink lib/fuse.c:fuse_release() with mutlithreading

[Mark H. <mar...@hu...>]

Hi,
I encountered a problem when using fuse and stressing my filesystem with
fsstress from LTP.
It is possible for the fuse code to call unlink in my fuse filesystem
before all releases of an open file have completed (tested with file
hiding on).

A case:
file XX is open 3 times by 3 different threads
unlink is called on that file
    fuse sees open count is not zero and hides file

Now it is possible that unlink on the hidden file is called in my fuse
filesystem before all releases are done executing,
for example

thread 1 currently runs
    close()
        fuse_release()
           --open //(becomes 2)
           myfuse->release()
linux switches threads to 2
    close()
        fuse_release()
           --open //(becomes 1)
           myfuse->release()
linux switches threads to 3
    close()
        fuse_release()
            --open   //(becomes 0)
            myfuse->release()
            myfuse->release() finished
            myfuse->unlink()
            myfuse->unlink() finished
        fuse_release() finished
linux switches threads to 1
       myfuse->release() continues when file is already unlinked

Shouldn't the decrementing of --node->open_count; in
lib/fuse.c:fuse_release()
come after
    if (f->op.release)
        fuse_do_release(f, path, fi);
and before
    if(unlink_hidden && path)
        f->op.unlink(path);

Regards,
Mark