[PATCH 3.16 037/192] udf: Fix deadlock between writeback and udf_setsize()

Ben Hutchings
2017-10-09T13:39:15Z

From: Jan Kara <jack@suse.cz>

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>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
fs/udf/inode.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

--- a/fs/udf/inode.c
+++ b/fs/udf/inode.c
@@ -1238,8 +1238,8 @@ int udf_setsize(struct inode *inode, lof
return err;
}
set_size:
- 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);
@@ -1256,9 +1256,9 @@ set_size:
udf_get_block);
if (err)
return err;
+ truncate_setsize(inode, newsize);
down_write(&iinfo->i_data_sem);
udf_clear_extent_cache(inode);
- truncate_setsize(inode, newsize);
udf_truncate_extents(inode);
up_write(&iinfo->i_data_sem);
}