linux-ext4 - [PATCH 3/5] ext4_zero_range: fix incorect journal credits reservation

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Message-Id: <1408707147-22482-4-git-send-email-dmonakhov@openvz.org>
Date:	Fri, 22 Aug 2014 15:32:25 +0400
From:	Dmitry Monakhov <dmonakhov@...nvz.org>
To:	linux-ext4@...r.kernel.org
Cc:	lczerner@...hat.com, Dmitry Monakhov <dmonakhov@...nvz.org>
Subject: [PATCH 3/5] ext4_zero_range: fix incorect journal credits reservation

Currently we reserve only 4 blocks but in worst case scenario
ext4_zero_partial_blocks() may want to zeroout and convert two
non adjacent blocks.

Signed-off-by: Dmitry Monakhov <dmonakhov@...nvz.org>
---
 fs/ext4/extents.c |    7 +++++--
 1 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index 5bf718b..39fbcbb 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -4740,6 +4740,7 @@ static long ext4_zero_range(struct file *file, loff_t offset,
 	loff_t new_size = 0;
 	int ret = 0;
 	int flags;
+	int credits;
 	int partial;
 	loff_t start, end;
 	ext4_lblk_t lblk;
@@ -4839,8 +4840,10 @@ static long ext4_zero_range(struct file *file, loff_t offset,
 		if (ret)
 			goto out_dio;
 	}
-
-	handle = ext4_journal_start(inode, EXT4_HT_MISC, 4);
+	/* In worst case we have to writeout two nonadjacent unwritten blocks */
+	credits = ext4_chunk_trans_blocks(inode, 1) * 2 -
+		EXT4_META_TRANS_BLOCKS(inode->i_sb);
+	handle = ext4_journal_start(inode, EXT4_HT_MISC, credits);
 	if (IS_ERR(handle)) {
 		ret = PTR_ERR(handle);
 		ext4_std_error(inode->i_sb, ret);
-- 
1.7.1

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