4.9-stable review patch. If anyone has any objections, please let me know.
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From: Eryu Guan guaneryu@gmail.com
commit 73fdad00b208b139cf43f3163fbc0f67e4c6047c upstream.
i_disksize update should be protected by i_data_sem, by either taking the lock explicitly or by using ext4_update_i_disksize() helper. But the i_disksize updates in ext4_direct_IO_write() are not protected at all, which may be racing with i_disksize updates in writeback path in delalloc buffer write path.
This is found by code inspection, and I didn't hit any i_disksize corruption due to this bug. Thanks to Jan Kara for catching this bug and suggesting the fix!
Reported-by: Jan Kara jack@suse.cz Suggested-by: Jan Kara jack@suse.cz Signed-off-by: Eryu Guan guaneryu@gmail.com Signed-off-by: Theodore Ts'o tytso@mit.edu Cc: stable@vger.kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- fs/ext4/inode.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-)
--- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -3396,7 +3396,6 @@ static ssize_t ext4_direct_IO_write(stru { struct file *file = iocb->ki_filp; struct inode *inode = file->f_mapping->host; - struct ext4_inode_info *ei = EXT4_I(inode); ssize_t ret; loff_t offset = iocb->ki_pos; size_t count = iov_iter_count(iter); @@ -3420,7 +3419,7 @@ static ssize_t ext4_direct_IO_write(stru goto out; } orphan = 1; - ei->i_disksize = inode->i_size; + ext4_update_i_disksize(inode, inode->i_size); ext4_journal_stop(handle); }
@@ -3548,7 +3547,7 @@ static ssize_t ext4_direct_IO_write(stru if (ret > 0) { loff_t end = offset + ret; if (end > inode->i_size) { - ei->i_disksize = end; + ext4_update_i_disksize(inode, end); i_size_write(inode, end); /* * We're going to return a positive `ret'