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Date:	Fri, 28 Sep 2012 19:44:08 +0400
From:	Dmitry Monakhov <dmonakhov@...nvz.org>
To:	linux-ext4@...r.kernel.org
Cc:	tytso@....edu, jack@...e.cz, lczerner@...hat.com,
	Dmitry Monakhov <dmonakhov@...nvz.org>
Subject: [PATCH 08/11] ext4: endless truncate due to nonlocked dio readers V2

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.

Signed-off-by: Dmitry Monakhov <dmonakhov@...nvz.org>
---
 fs/ext4/inode.c |    9 +++++++--
 1 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 583cb3f..c40a98d 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -4305,9 +4305,14 @@ int ext4_setattr(struct dentry *dentry, struct iattr *attr)
 	if (attr->ia_valid & ATTR_SIZE) {
 		if (attr->ia_size != inode->i_size) {
 			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);
 	}
-- 
1.7.7.6

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