ext4: endless truncate due to nonlocked dio readers

If we have enough aggressive DIO readers, truncate and other dio
waiters will wait forever inside inode_dio_wait(). It is reasonable
to disable nonlock DIO read optimization during truncate.

Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Dmitry Monakhov <dmonakhov@openvz.org>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

1 files changed, 7 insertions, 2 deletions

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 0bfc6333146..05ab70dd5c6 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -4333,9 +4333,14 @@ int ext4_setattr(struct dentry *dentry, struct iattr *attr)
         if (attr->ia_valid & ATTR_SIZE) {
                 if (attr->ia_size != i_size_read(inode)) {
                         truncate_setsize(inode, attr->ia_size);
-                        /* Inode size will be reduced, wait for dio in flight */
-                        if (orphan)
+                        /* Inode size will be reduced, wait for dio in flight.
+                         * Temporarily disable dioread_nolock to prevent
+                         * livelock. */
+                        if (orphan) {
+                                ext4_inode_block_unlocked_dio(inode);
                                 inode_dio_wait(inode);
+                                ext4_inode_resume_unlocked_dio(inode);
+                        }
                 }
                 ext4_truncate(inode);
         }