On Fri, 2007-11-09 at 16:26 -0500, Trond Myklebust wrote:
> > #include <linux/sunrpc/svc.h>
> > #include <linux/nfsd/nfsd.h>
> > #include <linux/nfsd/cache.h>
> > +#include <linux/file.h>
> > #include <linux/mount.h>
> > #include <linux/workqueue.h>
> > #include <linux/smp_lock.h>
> > @@ -1303,7 +1304,7 @@ static inline void
> > nfs4_file_downgrade(struct file *filp, unsigned int share_access)
> > {
> > if (share_access & NFS4_SHARE_ACCESS_WRITE) {
> > - put_write_access(filp->f_path.dentry->d_inode);
> > + drop_file_write_access(filp);
> > filp->f_mode = (filp->f_mode | FMODE_READ) & ~FMODE_WRITE;
> > }
> > }
>
> Hmm... The NFS server may also try to 'upgrade' an open file request to
> a read/write request whenever the client issues a new OPEN request for
> WRITE using the same open_owner.
Can you point me to some code? I'll try and go fix it up.
> > diff -puN fs/pipe.c~fix-idmapd-bug fs/pipe.c
> > --- linux-2.6.git/fs/pipe.c~fix-idmapd-bug 2007-11-09 12:13:15.000000000 -0800
> > +++ linux-2.6.git-dave/fs/pipe.c 2007-11-09 12:13:15.000000000 -0800
> > @@ -959,13 +959,10 @@ struct file *create_write_pipe(void)
> > struct dentry *dentry;
> > struct qstr name = { .name = "" };
> >
> > - f = get_empty_filp();
> > - if (!f)
> > - return ERR_PTR(-ENFILE);
> > err = -ENFILE;
> > inode = get_pipe_inode();
> > if (!inode)
> > - goto err_file;
> > + goto err;
> >
> > err = -ENOMEM;
> > dentry = d_alloc(pipe_mnt->mnt_sb->s_root, &name);
> > @@ -980,13 +977,14 @@ struct file *create_write_pipe(void)
> > */
> > dentry->d_flags &= ~DCACHE_UNHASHED;
> > d_instantiate(dentry, inode);
> > - f->f_path.mnt = mntget(pipe_mnt);
> > - f->f_path.dentry = dentry;
> > +
> > + f = alloc_file(pipe_mnt, dentry, FMODE_WRITE, &write_pipe_fops);
> > + err = -ENFILE;
> > + if (!f)
> > + goto err_inode;
> > f->f_mapping = inode->i_mapping;
> >
> > f->f_flags = O_WRONLY;
> > - f->f_op = &write_pipe_fops;
> > - f->f_mode = FMODE_WRITE;
> > f->f_version = 0;
> >
> > return f;
> > @@ -994,8 +992,7 @@ struct file *create_write_pipe(void)
> > err_inode:
> > free_pipe_info(inode);
> > iput(inode);
> > - err_file:
> > - put_filp(f);
> > + err:
> > return ERR_PTR(err);
> > }
>
> Does RPC idmapd open a regular pipe too? I thought it only used
> rpc_pipefs?
No. I the the actual bug triggered by idmapd was from an eventpoll filp
that had been acquired through anon_inode_getfd(). I just noticed the
pipe code here could be another potential bug of the same type.
-- Dave
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