From: Omar Sandoval <osandov@osandov.com>
Date: Thu, 8 Jan 2015 09:18:30 +0000 (-0800)
Subject: nfs: prevent truncate on active swapfile
X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=3a7ed3fff3bb22828f7d7ba6b75c7d22ee54df38;p=GitHub%2Fmoto-9609%2Fandroid_kernel_motorola_exynos9610.git

nfs: prevent truncate on active swapfile

Most filesystems prevent truncation of an active swapfile by way of
inode_newsize_ok, called from inode_change_ok. NFS doesn't call either
from nfs_setattr, presumably because most of these checks are expected
to be done server-side. However, the IS_SWAPFILE check can only be done
client-side, and truncating a swapfile can't possibly be good.

Signed-off-by: Omar Sandoval <osandov@osandov.com>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
---

diff --git a/fs/nfs/inode.c b/fs/nfs/inode.c
index 2211f6ba8736..d2398c193bda 100644
--- a/fs/nfs/inode.c
+++ b/fs/nfs/inode.c
@@ -507,10 +507,15 @@ nfs_setattr(struct dentry *dentry, struct iattr *attr)
 		attr->ia_valid &= ~ATTR_MODE;
 
 	if (attr->ia_valid & ATTR_SIZE) {
+		loff_t i_size;
+
 		BUG_ON(!S_ISREG(inode->i_mode));
 
-		if (attr->ia_size == i_size_read(inode))
+		i_size = i_size_read(inode);
+		if (attr->ia_size == i_size)
 			attr->ia_valid &= ~ATTR_SIZE;
+		else if (attr->ia_size < i_size && IS_SWAPFILE(inode))
+			return -ETXTBSY;
 	}
 
 	/* Optimization: if the end result is no change, don't RPC */