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Re: [PATCH] use proper mnt_want_write calls for handle ioctls

To: xfs@xxxxxxxxxxx
Subject: Re: [PATCH] use proper mnt_want_write calls for handle ioctls
From: Christoph Hellwig <hch@xxxxxx>
Date: Mon, 29 Sep 2008 09:42:34 +0200
In-reply-to: <20080912084431.GA22641@xxxxxx>
References: <20080814203952.GB18704@xxxxxx> <20080912084431.GA22641@xxxxxx>
User-agent: Mutt/1.3.28i
ping^2?

On Fri, Sep 12, 2008 at 10:44:31AM +0200, Christoph Hellwig wrote:
> ping?  Without this patch the CVS tree won't properly work with
> read-only bind mounts.
> 
> On Thu, Aug 14, 2008 at 10:39:52PM +0200, Christoph Hellwig wrote:
> > Since 2.6.26 all writes to filesystems need to be enclosed by a
> > mnt_want_write / mnt_drop_write pair instead of checking for IS_RDONLY.
> > 
> > XFs was updated for this in mainline but the changes to xfs_ioctl.c
> > were never megred back into the CVS tree.
> > 
> > The original commit introducing this was:
> > 
> > commit 42a74f206b914db13ee1f5ae932dcd91a77c8579
> > Author: Dave Hansen <haveblue@xxxxxxxxxx>
> > Date:   Fri Feb 15 14:37:46 2008 -0800
> > 
> >     [PATCH] r/o bind mounts: elevate write count for ioctls()
> > 
> > Index: linux-2.6-xfs/fs/xfs/linux-2.6/xfs_ioctl.c
> > ===================================================================
> > --- linux-2.6-xfs.orig/fs/xfs/linux-2.6/xfs_ioctl.c 2008-08-14 
> > 14:54:53.000000000 -0300
> > +++ linux-2.6-xfs/fs/xfs/linux-2.6/xfs_ioctl.c      2008-08-14 
> > 15:15:49.000000000 -0300
> > @@ -543,8 +543,6 @@ xfs_attrmulti_attr_set(
> >     char                    *kbuf;
> >     int                     error = EFAULT;
> >  
> > -   if (IS_RDONLY(inode))
> > -           return -EROFS;
> >     if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
> >             return EPERM;
> >     if (len > XATTR_SIZE_MAX)
> > @@ -570,8 +568,6 @@ xfs_attrmulti_attr_remove(
> >     char                    *name,
> >     __uint32_t              flags)
> >  {
> > -   if (IS_RDONLY(inode))
> > -           return -EROFS;
> >     if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
> >             return EPERM;
> >     return xfs_attr_remove(XFS_I(inode), name, flags);
> > @@ -581,6 +577,7 @@ STATIC int
> >  xfs_attrmulti_by_handle(
> >     xfs_mount_t             *mp,
> >     void                    __user *arg,
> > +   struct file             *parfilp,
> >     struct inode            *parinode)
> >  {
> >     int                     error;
> > @@ -634,13 +631,21 @@ xfs_attrmulti_by_handle(
> >                                     &ops[i].am_length, ops[i].am_flags);
> >                     break;
> >             case ATTR_OP_SET:
> > +                   ops[i].am_error = mnt_want_write(parfilp->f_path.mnt);
> > +                   if (ops[i].am_error)
> > +                           break;
> >                     ops[i].am_error = xfs_attrmulti_attr_set(inode,
> >                                     attr_name, ops[i].am_attrvalue,
> >                                     ops[i].am_length, ops[i].am_flags);
> > +                   mnt_drop_write(parfilp->f_path.mnt);
> >                     break;
> >             case ATTR_OP_REMOVE:
> > +                   ops[i].am_error = mnt_want_write(parfilp->f_path.mnt);
> > +                   if (ops[i].am_error)
> > +                           break;
> >                     ops[i].am_error = xfs_attrmulti_attr_remove(inode,
> >                                     attr_name, ops[i].am_flags);
> > +                   mnt_drop_write(parfilp->f_path.mnt);
> >                     break;
> >             default:
> >                     ops[i].am_error = EINVAL;
> > @@ -1431,7 +1436,7 @@ xfs_ioctl(
> >             return xfs_attrlist_by_handle(mp, arg, inode);
> >  
> >     case XFS_IOC_ATTRMULTI_BY_HANDLE:
> > -           return xfs_attrmulti_by_handle(mp, arg, inode);
> > +           return xfs_attrmulti_by_handle(mp, arg, filp, inode);
> >  
> >     case XFS_IOC_SWAPEXT: {
> >             error = xfs_swapext((struct xfs_swapext __user *)arg);
> ---end quoted text---
---end quoted text---

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