From: Jan Kara <jack@suse.cz>
Date: Tue, 13 Jun 2017 14:20:25 +0000 (+0200)
Subject: udf: Fix deadlock between writeback and udf_setsize()
X-Git-Tag: v3.2.94~63
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=af64015b4f713ad1d63761c3d5c0f1e486677a72;p=thirdparty%2Fkernel%2Fstable.git

udf: Fix deadlock between writeback and udf_setsize()

commit f2e95355891153f66d4156bf3a142c6489cd78c6 upstream.

udf_setsize() called truncate_setsize() with i_data_sem held. Thus
truncate_pagecache() called from truncate_setsize() could lock a page
under i_data_sem which can deadlock as page lock ranks below
i_data_sem - e. g. writeback can hold page lock and try to acquire
i_data_sem to map a block.

Fix the problem by moving truncate_setsize() calls from under
i_data_sem. It is safe for us to change i_size without holding
i_data_sem as all the places that depend on i_size being stable already
hold inode_lock.

Fixes: 7e49b6f2480cb9a9e7322a91592e56a5c85361f5
Signed-off-by: Jan Kara <jack@suse.cz>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---

diff --git a/fs/udf/inode.c b/fs/udf/inode.c
index 5d67e2023311e..68de1c75237aa 100644
--- a/fs/udf/inode.c
+++ b/fs/udf/inode.c
@@ -1145,8 +1145,8 @@ int udf_setsize(struct inode *inode, loff_t newsize)
 			up_write(&iinfo->i_data_sem);
 			return err;
 		}
-		truncate_setsize(inode, newsize);
 		up_write(&iinfo->i_data_sem);
+		truncate_setsize(inode, newsize);
 	} else {
 		if (iinfo->i_alloc_type == ICBTAG_FLAG_AD_IN_ICB) {
 			down_write(&iinfo->i_data_sem);
@@ -1162,8 +1162,8 @@ int udf_setsize(struct inode *inode, loff_t newsize)
 					  udf_get_block);
 		if (err)
 			return err;
-		down_write(&iinfo->i_data_sem);
 		truncate_setsize(inode, newsize);
+		down_write(&iinfo->i_data_sem);
 		udf_truncate_extents(inode);
 		up_write(&iinfo->i_data_sem);
 	}