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Date: Mon, 13 Jan 2020 14:22:12 -0800 From: "Darrick J. Wong" <darrick.wong@...cle.com> To: ira.weiny@...el.com Cc: linux-kernel@...r.kernel.org, Alexander Viro <viro@...iv.linux.org.uk>, Dan Williams <dan.j.williams@...el.com>, Dave Chinner <david@...morbit.com>, Christoph Hellwig <hch@....de>, "Theodore Y. Ts'o" <tytso@....edu>, Jan Kara <jack@...e.cz>, linux-ext4@...r.kernel.org, linux-xfs@...r.kernel.org, linux-fsdevel@...r.kernel.org Subject: Re: [RFC PATCH V2 09/12] fs: Prevent mode change if file is mmap'ed On Fri, Jan 10, 2020 at 11:29:39AM -0800, ira.weiny@...el.com wrote: > From: Ira Weiny <ira.weiny@...el.com> > > Page faults need to ensure the inode mode is correct and consistent with > the vmf information at the time of the fault. There is no easy way to > ensure the vmf information is correct if a mode change is in progress. > Furthermore, there is no good use case to require a mode change while > the file is mmap'ed. > > Track mmap's of the file and fail the mode change if the file is > mmap'ed. > > Signed-off-by: Ira Weiny <ira.weiny@...el.com> > --- > fs/inode.c | 2 ++ > fs/xfs/xfs_ioctl.c | 8 ++++++++ > include/linux/fs.h | 1 + > mm/mmap.c | 19 +++++++++++++++++-- > 4 files changed, 28 insertions(+), 2 deletions(-) > > diff --git a/fs/inode.c b/fs/inode.c > index 2b0f51161918..944711aed6f8 100644 > --- a/fs/inode.c > +++ b/fs/inode.c > @@ -245,6 +245,8 @@ static struct inode *alloc_inode(struct super_block *sb) > return NULL; > } > > + atomic64_set(&inode->i_mapped, 0); > + > return inode; > } > > diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c > index bc3654fe3b5d..1ab0906c6c7f 100644 > --- a/fs/xfs/xfs_ioctl.c > +++ b/fs/xfs/xfs_ioctl.c > @@ -1200,6 +1200,14 @@ xfs_ioctl_setattr_dax_invalidate( > goto out_unlock; > } > > + /* > + * If there is a mapping in place we must remain in our current mode. > + */ > + if (atomic64_read(&inode->i_mapped)) { Urk, should we really be messing around with the address space internals? > + error = -EBUSY; > + goto out_unlock; > + } > + > error = filemap_write_and_wait(inode->i_mapping); > if (error) > goto out_unlock; > diff --git a/include/linux/fs.h b/include/linux/fs.h > index 631f11d6246e..6e7dc626b657 100644 > --- a/include/linux/fs.h > +++ b/include/linux/fs.h > @@ -740,6 +740,7 @@ struct inode { > #endif > > void *i_private; /* fs or device private pointer */ > + atomic64_t i_mapped; I would have expected to find this in struct address_space since the mapping count is a function of the address space, right? --D > } __randomize_layout; > > struct timespec64 timestamp_truncate(struct timespec64 t, struct inode *inode); > diff --git a/mm/mmap.c b/mm/mmap.c > index dfaf1130e706..e6b68924b7ca 100644 > --- a/mm/mmap.c > +++ b/mm/mmap.c > @@ -171,12 +171,17 @@ void unlink_file_vma(struct vm_area_struct *vma) > static struct vm_area_struct *remove_vma(struct vm_area_struct *vma) > { > struct vm_area_struct *next = vma->vm_next; > + struct file *f = vma->vm_file; > > might_sleep(); > if (vma->vm_ops && vma->vm_ops->close) > vma->vm_ops->close(vma); > - if (vma->vm_file) > - fput(vma->vm_file); > + if (f) { > + struct inode *inode = file_inode(f); > + if (inode) > + atomic64_dec(&inode->i_mapped); > + fput(f); > + } > mpol_put(vma_policy(vma)); > vm_area_free(vma); > return next; > @@ -1837,6 +1842,16 @@ unsigned long mmap_region(struct file *file, unsigned long addr, > > vma_set_page_prot(vma); > > + /* > + * Track if there is mapping in place such that a mode change > + * does not occur on a file which is mapped > + */ > + if (file) { > + struct inode *inode = file_inode(file); > + > + atomic64_inc(&inode->i_mapped); > + } > + > return addr; > > unmap_and_free_vma: > -- > 2.21.0 >
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