POSIX requires that "If the file size is increased, the extended area
shall appear as if it were zero-filled". It is possible to use mmap to
write past EOF and that data will become visible instead of zeroes.
This fixes the problem for the filesystems which simply call
truncate_setsize(). More complex filesystems will need their own
patches.
Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
---
mm/truncate.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/mm/truncate.c b/mm/truncate.c
index 7b4ea4c4a46b..cebfc5415e9a 100644
--- a/mm/truncate.c
+++ b/mm/truncate.c
@@ -763,9 +763,12 @@ void truncate_setsize(struct inode *inode, loff_t newsize)
loff_t oldsize = inode->i_size;
i_size_write(inode, newsize);
- if (newsize > oldsize)
+ if (newsize > oldsize) {
pagecache_isize_extended(inode, oldsize, newsize);
- truncate_pagecache(inode, newsize);
+ truncate_pagecache(inode, oldsize);
+ } else {
+ truncate_pagecache(inode, newsize);
+ }
}
EXPORT_SYMBOL(truncate_setsize);
--
2.35.1
