fix truncate inode time modification breakage

mtime and ctime should be changed only if the file size has actually
changed. Patches changing ext2 and tmpfs from vmtruncate to new truncate
sequence has caused regressions where they always update timestamps.

There is some strange cases in POSIX where truncate(2) must not update
times unless the size has acutally changed, see 6e656be89.

This area is all still rather buggy in different ways in a lot of
filesystems and needs a cleanup and audit (ideally the vfs will provide
a simple attribute or call to direct all filesystems exactly which
attributes to change). But coming up with the best solution will take a
while and is not appropriate for rc anyway.

So fix recent regression for now.

Signed-off-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 1 insertions, 1 deletions

diff --git a/fs/ext2/inode.c b/fs/ext2/inode.c
index 19214435b752..3675088cb88c 100644
--- a/fs/ext2/inode.c
+++ b/fs/ext2/inode.c
@@ -1552,7 +1552,7 @@ int ext2_setattr(struct dentry *dentry, struct iattr *iattr)
 		if (error)
 			return error;
 	}
-	if (iattr->ia_valid & ATTR_SIZE) {
+	if (iattr->ia_valid & ATTR_SIZE && iattr->ia_size != inode->i_size) {
 		error = ext2_setsize(inode, iattr->ia_size);
 		if (error)
 			return error;