In message <1194280730.6271.145.camel@localhost>, Dave Hansen writes: > On Mon, 2007-11-05 at 15:40 +0000, Hugh Dickins wrote: [...] > I have a decent guess what the bug is, too. In the unionfs code: > > > int init_lower_nd(struct nameidata *nd, unsigned int flags) > > { > > ... > > #ifdef ALLOC_LOWER_ND_FILE > > file = kzalloc(sizeof(struct file), GFP_KERNEL); > > if (unlikely(!file)) { > > err = -ENOMEM; > > break; /* exit switch statement and thus return */ > > } > > nd->intent.open.file = file; > > #endif /* ALLOC_LOWER_ND_FILE */ > > The r/o bind mount code will mnt_drop_write() on that file's f_vfsmnt at > __fput() time. Since that code never got a write on the mount, we'll > see an imbalance if the file was opened for a write. I don't see this > file's mnt set anywhere, so I'm not completely sure that this is it. In > any case, rolling your own 'struct file' without using alloc_file() and > friends is a no-no. [...] This #ifdef'd code in unionfs is actually not enabled. I left it there as a reminder of possible future things to come (esp. if nameidata gets split). There's a related comment earlier in fs/unionfs/lookup.c:init_lower_nd() that says: #ifdef ALLOC_LOWER_ND_FILE /* * XXX: one day we may need to have the lower return an open file * for us. It is not needed in 2.6.23-rc1 for nfs2/nfs3, but may * very well be needed for nfs4. */ struct file *file; #endif /* ALLOC_LOWER_ND_FILE */ In the interest of keeping unionfs as simple as I can, when I implemented the whole "pass a lower nd" stuff, I left thos bits of semi-experimental #ifdef code for this lower file upon open-intent. It's not enabled and up until now, it didn't seem to be needed. Do you think unionfs has to start using this nd->intent.open.file stuff? Thanks, Erez. - To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
