linux-ext4 - [PATCH] ext4: block direct I/O writes during ext4

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Message-Id: <1373861479-15136-1-git-send-email-tytso@mit.edu>
Date:	Mon, 15 Jul 2013 00:11:19 -0400
From:	Theodore Ts'o <tytso@....edu>
To:	Ext4 Developers List <linux-ext4@...r.kernel.org>
Cc:	Theodore Ts'o <tytso@....edu>, stable@...r.kernel.org
Subject: [PATCH] ext4: block direct I/O writes during ext4_truncate

Just as in ext4_punch_hole() it is important that we block DIO writes
while the truncate is proceeding, since during the overwriting DIO
write, we drop i_mutex, which means a truncate could start while the
Direct I/O operation is still in progress.

Signed-off-by: "Theodore Ts'o" <tytso@....edu>
Cc: stable@...r.kernel.org
---
 fs/ext4/inode.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 98b9bff..3c5edf2 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -3659,12 +3659,16 @@ void ext4_truncate(struct inode *inode)
 	if (inode->i_size == 0 && !test_opt(inode->i_sb, NO_AUTO_DA_ALLOC))
 		ext4_set_inode_state(inode, EXT4_STATE_DA_ALLOC_CLOSE);
 
+	/* Wait all existing dio workers, newcomers will block on i_mutex */
+	ext4_inode_block_unlocked_dio(inode);
+	inode_dio_wait(inode);
+
 	if (ext4_has_inline_data(inode)) {
 		int has_inline = 1;
 
 		ext4_inline_data_truncate(inode, &has_inline);
 		if (has_inline)
-			return;
+			goto out_resume;
 	}
 
 	if (ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))
@@ -3675,7 +3679,7 @@ void ext4_truncate(struct inode *inode)
 	handle = ext4_journal_start(inode, EXT4_HT_TRUNCATE, credits);
 	if (IS_ERR(handle)) {
 		ext4_std_error(inode->i_sb, PTR_ERR(handle));
-		return;
+		goto out_resume;
 	}
 
 	if (inode->i_size & (inode->i_sb->s_blocksize - 1))
@@ -3722,6 +3726,8 @@ out_stop:
 	ext4_mark_inode_dirty(handle, inode);
 	ext4_journal_stop(handle);
 
+out_resume:
+	ext4_inode_resume_unlocked_dio(inode);
 	trace_ext4_truncate_exit(inode);
 }
 
-- 
1.7.12.rc0.22.gcdd159b

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