fuse: lock page in mkwrite

Lock the page in fuse_page_mkwrite() to protect against a race with
fuse_writepage() where the page is redirtied before the actual writeback
begins.

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>

diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index 944acc0..6fb9425 100644 (file)
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -1618,14 +1618,17 @@ static void fuse_vma_close(struct vm_area_struct *vma)
 static int fuse_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
 {
        struct page *page = vmf->page;
-       /*
-        * Don't use page->mapping as it may become NULL from a
-        * concurrent truncate.
-        */
-       struct inode *inode = vma->vm_file->f_mapping->host;
+       struct inode *inode = file_inode(vma->vm_file);
+
+       file_update_time(vma->vm_file);
+       lock_page(page);
+       if (page->mapping != inode->i_mapping) {
+               unlock_page(page);
+               return VM_FAULT_NOPAGE;
+       }
 
        fuse_wait_on_page_writeback(inode, page->index);
-       return 0;
+       return VM_FAULT_LOCKED;
 }
 
 static const struct vm_operations_struct fuse_file_vm_ops = {