[PATCH] mm: Fix comment before truncate_setsize()

[Jan Kara <jack@suse.cz>]

XFS doesn't always hold i_mutex when calling truncate_setsize() and it
uses a different lock to serialize truncates and writes. So fix the
comment before truncate_setsize().

Reported-by: Jan Beulich <JBeulich@suse.com>
Signed-off-by: Jan Kara <jack@suse.cz>
---
 mm/truncate.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/mm/truncate.c b/mm/truncate.c
index b248c0c8dcd1..ed33e8f811e9 100644
--- a/mm/truncate.c
+++ b/mm/truncate.c
@@ -715,8 +715,9 @@ EXPORT_SYMBOL(truncate_pagecache);
  * necessary) to @newsize. 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 before all filesystem specific
- * block truncation has been performed.
+ * Must be called with a lock serializing truncates and writes (generally
+ * i_mutex but e.g. xfs uses a different lock) and before all filesystem
+ * specific block truncation has been performed.
  */
 void truncate_setsize(struct inode *inode, loff_t newsize)
 {
-- 
1.8.1.4

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