fs/9p: Use truncate_setsize instead of vmtruncate

convert vmtruncate usage to truncate_setsize. We also writeback
all dirty pages before doing 9p operations and on success call truncate_setsize.
This ensure that we continue sanely on failed truncate on the server. The
disadvantage is that we are now going to write back the content that get
thrown away later as a part of truncate.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Venkateswararao Jujjuri <jvrao@linux.vnet.ibm.com>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>

fs/9p/vfs_inode.c

@@ -971,6 +971,10 @@ static int v9fs_vfs_setattr(struct dentry *dentry, struct iattr *iattr)
 	struct p9_wstat wstat;
 
 	P9_DPRINTK(P9_DEBUG_VFS, "\n");
+	retval = inode_change_ok(dentry->d_inode, iattr);
+	if (retval)
+		return retval;
+
 	retval = -EPERM;
 	v9ses = v9fs_inode2v9ses(dentry->d_inode);
 	fid = v9fs_fid_lookup(dentry);
@@ -997,12 +1001,7 @@ static int v9fs_vfs_setattr(struct dentry *dentry, struct iattr *iattr)
 		if (iattr->ia_valid & ATTR_GID)
 			wstat.n_gid = iattr->ia_gid;
 	}
-	if ((iattr->ia_valid & ATTR_SIZE) &&
-	    iattr->ia_size != i_size_read(dentry->d_inode)) {
-		retval = vmtruncate(dentry->d_inode, iattr->ia_size);
-		if (retval)
-			return retval;
-	}
+
 	/* Write all dirty data */
 	if (S_ISREG(dentry->d_inode->i_mode))
 		filemap_write_and_wait(dentry->d_inode->i_mapping);
@@ -1010,6 +1009,11 @@ static int v9fs_vfs_setattr(struct dentry *dentry, struct iattr *iattr)
 	retval = p9_client_wstat(fid, &wstat);
 	if (retval < 0)
 		return retval;
+
+	if ((iattr->ia_valid & ATTR_SIZE) &&
+	    iattr->ia_size != i_size_read(dentry->d_inode))
+		truncate_setsize(dentry->d_inode, iattr->ia_size);
+
 	v9fs_invalidate_inode_attr(dentry->d_inode);
 
 	setattr_copy(dentry->d_inode, iattr);

fs/9p/vfs_inode_dotl.c

@@ -456,12 +456,6 @@ int v9fs_vfs_setattr_dotl(struct dentry *dentry, struct iattr *iattr)
 	if (IS_ERR(fid))
 		return PTR_ERR(fid);
 
-	if ((iattr->ia_valid & ATTR_SIZE) &&
-	    iattr->ia_size != i_size_read(dentry->d_inode)) {
-		retval = vmtruncate(dentry->d_inode, iattr->ia_size);
-		if (retval)
-			return retval;
-	}
 	/* Write all dirty data */
 	if (S_ISREG(dentry->d_inode->i_mode))
 		filemap_write_and_wait(dentry->d_inode->i_mapping);
@@ -469,8 +463,12 @@ int v9fs_vfs_setattr_dotl(struct dentry *dentry, struct iattr *iattr)
 	retval = p9_client_setattr(fid, &p9attr);
 	if (retval < 0)
 		return retval;
-	v9fs_invalidate_inode_attr(dentry->d_inode);
 
+	if ((iattr->ia_valid & ATTR_SIZE) &&
+	    iattr->ia_size != i_size_read(dentry->d_inode))
+		truncate_setsize(dentry->d_inode, iattr->ia_size);
+
+	v9fs_invalidate_inode_attr(dentry->d_inode);
 	setattr_copy(dentry->d_inode, iattr);
 	mark_inode_dirty(dentry->d_inode);
 	if (iattr->ia_valid & ATTR_MODE) {