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-rw-r--r--fs/ocfs2/mmap.c8
1 files changed, 5 insertions, 3 deletions
diff --git a/fs/ocfs2/mmap.c b/fs/ocfs2/mmap.c
index af2b8fe1f13..4c18f4ad93b 100644
--- a/fs/ocfs2/mmap.c
+++ b/fs/ocfs2/mmap.c
@@ -74,9 +74,11 @@ static int __ocfs2_page_mkwrite(struct inode *inode, struct buffer_head *di_bh,
/*
* Another node might have truncated while we were waiting on
* cluster locks.
+ * We don't check size == 0 before the shift. This is borrowed
+ * from do_generic_file_read.
*/
- last_index = size >> PAGE_CACHE_SHIFT;
- if (page->index > last_index) {
+ last_index = (size - 1) >> PAGE_CACHE_SHIFT;
+ if (unlikely(!size || page->index > last_index)) {
ret = -EINVAL;
goto out;
}
@@ -107,7 +109,7 @@ static int __ocfs2_page_mkwrite(struct inode *inode, struct buffer_head *di_bh,
* because the "write" would invalidate their data.
*/
if (page->index == last_index)
- len = size & ~PAGE_CACHE_MASK;
+ len = ((size - 1) & ~PAGE_CACHE_MASK) + 1;
ret = ocfs2_write_begin_nolock(mapping, pos, len, 0, &locked_page,
&fsdata, di_bh, page);