[PATCH 2/2] udf: Fix lock ordering in udf_evict_inode()

[Jan Kara <jack@suse.cz>]

udf_evict_inode() calls udf_setsize() to truncate deleted inode.
However inode deletion through udf_evict_inode() can happen from inode
reclaim context and udf_setsize() grabs mapping->invalidate_lock which
isn't generally safe to acquire from fs reclaim context since we
allocate pages under mapping->invalidate_lock for example in a page
fault path.  This is however not a real deadlock possibility as by the
time udf_evict_inode() is called, nobody can be accessing the inode,
even less work with its page cache. So this is just a lockdep triggering
false positive. Fix the problem by moving mapping->invalidate_lock
locking outsize of udf_setsize() into udf_setattr() as grabbing
mapping->invalidate_lock from udf_evict_inode() is pointless.

Reported-by: syzbot+0333a6f4b88bcd68a62f@syzkaller.appspotmail.com
Fixes: b9a861fd527a ("udf: Protect truncate and file type conversion with invalidate_lock")
Signed-off-by: Jan Kara <jack@suse.cz>
---
 fs/udf/file.c  |  2 ++
 fs/udf/inode.c | 11 ++++-------
 2 files changed, 6 insertions(+), 7 deletions(-)

diff --git a/fs/udf/file.c b/fs/udf/file.c
index 0ceac4b5937c..94daaaf76f71 100644
--- a/fs/udf/file.c
+++ b/fs/udf/file.c
@@ -232,7 +232,9 @@ static int udf_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
 
 	if ((attr->ia_valid & ATTR_SIZE) &&
 	    attr->ia_size != i_size_read(inode)) {
+		filemap_invalidate_lock(inode->i_mapping);
 		error = udf_setsize(inode, attr->ia_size);
+		filemap_invalidate_unlock(inode->i_mapping);
 		if (error)
 			return error;
 	}
diff --git a/fs/udf/inode.c b/fs/udf/inode.c
index 04b0e62cf73f..87002ecd79df 100644
--- a/fs/udf/inode.c
+++ b/fs/udf/inode.c
@@ -1249,7 +1249,6 @@ int udf_setsize(struct inode *inode, loff_t newsize)
 	      S_ISLNK(inode->i_mode)))
 		return -EINVAL;
 
-	filemap_invalidate_lock(inode->i_mapping);
 	iinfo = UDF_I(inode);
 	if (newsize > inode->i_size) {
 		if (iinfo->i_alloc_type == ICBTAG_FLAG_AD_IN_ICB) {
@@ -1262,11 +1261,11 @@ int udf_setsize(struct inode *inode, loff_t newsize)
 			}
 			err = udf_expand_file_adinicb(inode);
 			if (err)
-				goto out_unlock;
+				return err;
 		}
 		err = udf_extend_file(inode, newsize);
 		if (err)
-			goto out_unlock;
+			return err;
 set_size:
 		truncate_setsize(inode, newsize);
 	} else {
@@ -1284,14 +1283,14 @@ int udf_setsize(struct inode *inode, loff_t newsize)
 		err = block_truncate_page(inode->i_mapping, newsize,
 					  udf_get_block);
 		if (err)
-			goto out_unlock;
+			return err;
 		truncate_setsize(inode, newsize);
 		down_write(&iinfo->i_data_sem);
 		udf_clear_extent_cache(inode);
 		err = udf_truncate_extents(inode);
 		up_write(&iinfo->i_data_sem);
 		if (err)
-			goto out_unlock;
+			return err;
 	}
 update_time:
 	inode_set_mtime_to_ts(inode, inode_set_ctime_current(inode));
@@ -1299,8 +1298,6 @@ int udf_setsize(struct inode *inode, loff_t newsize)
 		udf_sync_inode(inode);
 	else
 		mark_inode_dirty(inode);
-out_unlock:
-	filemap_invalidate_unlock(inode->i_mapping);
 	return err;
 }
 
-- 
2.35.3