[PATCH 1/8] xfs: mmap lock needs to be inside freeze protection

Dave Chinner
2015-05-28T23:46:11Z

From: Dave Chinner <dchinner@redhat.com>

Lock ordering for the new mmap lock needs to be:

mmap_sem
sb_start_pagefault
i_mmap_lock
page lock
<fault processsing>

Right now xfs_vm_page_mkwrite gets this the wrong way around,
While technically it cannot deadlock due to the current freeze
ordering, it's still a landmine that might explode if we change
anything in future. Hence we need to nest the locks correctly.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
---
fs/xfs/xfs_file.c | 11 ++++++++---
1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index 3b75912..4a0af89 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -1487,15 +1487,20 @@ xfs_filemap_page_mkwrite(
struct vm_fault *vmf)
{
struct xfs_inode *ip = XFS_I(vma->vm_file->f_mapping->host);
- int error;
+ int ret;

trace_xfs_filemap_page_mkwrite(ip);

+ sb_start_pagefault(VFS_I(ip)->i_sb);
+ file_update_time(vma->vm_file);
xfs_ilock(ip, XFS_MMAPLOCK_SHARED);
- error = block_page_mkwrite(vma, vmf, xfs_get_blocks);
+
+ ret = __block_page_mkwrite(vma, vmf, xfs_get_blocks);
+
xfs_iunlock(ip, XFS_MMAPLOCK_SHARED);
+ sb_end_pagefault(VFS_I(ip)->i_sb);

- return error;
+ return block_page_mkwrite_return(ret);
}

const struct file_operations xfs_file_operations = {
--
2.0.0