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From 69e4026a2d104ffcf1b935bc889f8abcbfbb29ec Mon Sep 17 00:00:00 2001
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From: Dmitry Monakhov <dmonakhov@openvz.org>
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Date: Sat, 29 Sep 2012 00:58:26 -0400
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Subject: [PATCH 08/13] ext4: serialize truncate with owerwrite DIO workers
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Jan Kara have spotted interesting issue:
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There are potential data corruption issue with direct IO overwrites
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racing with truncate:
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Like:
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dio write truncate_task
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->ext4_ext_direct_IO
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->overwrite == 1
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->down_read(&EXT4_I(inode)->i_data_sem);
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->mutex_unlock(&inode->i_mutex);
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->ext4_setattr()
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->inode_dio_wait()
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->truncate_setsize()
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->ext4_truncate()
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->down_write(&EXT4_I(inode)->i_data_sem);
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->__blockdev_direct_IO
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->ext4_get_block
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->submit_io()
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->up_read(&EXT4_I(inode)->i_data_sem);
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# truncate data blocks, allocate them to
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# other inode - bad stuff happens because
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# dio is still in flight.
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In order to serialize with truncate dio worker should grab extra i_dio_count
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reference before drop i_mutex.
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Reviewed-by: Jan Kara <jack@suse.cz>
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Signed-off-by: Dmitry Monakhov <dmonakhov@openvz.org>
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Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
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(cherry picked from commit 1f555cfa29e8f787d675e8390f88ce517a37271a)
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---
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fs/ext4/inode.c | 2 ++
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1 file changed, 2 insertions(+)
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diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
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index 3b03dd6..484a327 100644
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--- a/fs/ext4/inode.c
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+++ b/fs/ext4/inode.c
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@@ -3008,6 +3008,7 @@ static ssize_t ext4_ext_direct_IO(int rw, struct kiocb *iocb,
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overwrite = *((int *)iocb->private);
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if (overwrite) {
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+ atomic_inc(&inode->i_dio_count);
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down_read(&EXT4_I(inode)->i_data_sem);
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mutex_unlock(&inode->i_mutex);
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}
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@@ -3105,6 +3106,7 @@ static ssize_t ext4_ext_direct_IO(int rw, struct kiocb *iocb,
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retake_lock:
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/* take i_mutex locking again if we do a ovewrite dio */
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if (overwrite) {
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+ inode_dio_done(inode);
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up_read(&EXT4_I(inode)->i_data_sem);
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mutex_lock(&inode->i_mutex);
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}
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--
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1.7.12.rc0.22.gcdd159b
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