On Fri, 23 Mar 2012 14:14:54 -0700 (PDT)
Hugh Dickins [off-list ref] wrote:

On Fri, 23 Mar 2012, Andrew Morton wrote:

quoted

--- a/mm/truncate.c~mm-for-fs-add-truncate_pagecache_range-fix
+++ a/mm/truncate.c

@@ -639,6 +639,9 @@ int vmtruncate_range(struct inode *inode
  * with on-disk format, and the filesystem would not have to deal with
  * situations such as writepage being called for a page that has already
  * had its underlying blocks deallocated.
+ *
+ * Must be called with inode->i_mapping->i_mutex held.

You catch me offguard: I forget whether that's an absolute requirement or
just commonly the case.  What do the other interfaces in truncate.c say ?-)

i_mutex is generally required, to stabilise i_size.

quoted

+ * Takes inode->i_mapping->i_mmap_mutex.

Yes, and inode->i_mapping->tree_lock.

I don't think it's necessary to get into the spinning locks for a
high-level function which clearly does sleeping things.


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