check ATTR_SIZE contraints in inode_change_ok

Make sure we check the truncate constraints early on in ->setattr by adding
those checks to inode_change_ok.  Also clean up and document inode_change_ok
to make this obvious.

As a fallout we don't have to call inode_newsize_ok from simple_setsize and
simplify it down to a truncate_setsize which doesn't return an error.  This
simplifies a lot of setattr implementations and means we use truncate_setsize
almost everywhere.  Get rid of fat_setsize now that it's trivial and mark
ext2_setsize static to make the calling convention obvious.

Keep the inode_newsize_ok in vmtruncate for now as all callers need an
audit for its removal anyway.

Note: setattr code in ecryptfs doesn't call inode_change_ok at all and
needs a deeper audit, but that is left for later.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

2 files changed, 31 insertions, 12 deletions

diff --git a/mm/shmem.c b/mm/shmem.c
index 0a43505..33222ba 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -805,11 +805,10 @@ static int shmem_notify_change(struct dentry *dentry, struct iattr *attr)
 			}
 		}
 
-		error = simple_setsize(inode, newsize);
+		/* XXX(truncate): truncate_setsize should be called last */
+		truncate_setsize(inode, newsize);
 		if (page)
 			page_cache_release(page);
-		if (error)
-			return error;
 		shmem_truncate_range(inode, newsize, (loff_t)-1);
 	}
 
diff --git a/mm/truncate.c b/mm/truncate.c
index 937571b..ba887bf 100644
--- a/mm/truncate.c
+++ b/mm/truncate.c
@@ -541,28 +541,48 @@ void truncate_pagecache(struct inode *inode, loff_t old, loff_t new)
 EXPORT_SYMBOL(truncate_pagecache);
 
 /**
+ * truncate_setsize - update inode and pagecache for a new file size
+ * @inode: inode
+ * @newsize: new file size
+ *
+ * truncate_setsize updastes i_size update and performs pagecache
+ * truncation (if necessary) for a file size updates. It will be
+ * typically be called from the filesystem's setattr function when
+ * ATTR_SIZE is passed in.
+ *
+ * Must be called with inode_mutex held and after all filesystem
+ * specific block truncation has been performed.
+ */
+void truncate_setsize(struct inode *inode, loff_t newsize)
+{
+	loff_t oldsize;
+
+	oldsize = inode->i_size;
+	i_size_write(inode, newsize);
+
+	truncate_pagecache(inode, oldsize, newsize);
+}
+EXPORT_SYMBOL(truncate_setsize);
+
+/**
  * vmtruncate - unmap mappings "freed" by truncate() syscall
  * @inode: inode of the file used
  * @offset: file offset to start truncating
  *
- * NOTE! We have to be ready to update the memory sharing
- * between the file and the memory map for a potential last
- * incomplete page.  Ugly, but necessary.
- *
- * This function is deprecated and simple_setsize or truncate_pagecache
- * should be used instead.
+ * This function is deprecated and truncate_setsize or truncate_pagecache
+ * should be used instead, together with filesystem specific block truncation.
  */
 int vmtruncate(struct inode *inode, loff_t offset)
 {
 	int error;
 
-	error = simple_setsize(inode, offset);
+	error = inode_newsize_ok(inode, offset);
 	if (error)
 		return error;
 
+	truncate_setsize(inode, offset);
 	if (inode->i_op->truncate)
 		inode->i_op->truncate(inode);
-
-	return error;
+	return 0;
 }
 EXPORT_SYMBOL(vmtruncate);