linux-ext4 - Re: [PATCH] ext4: use directio end_io error status to finish unwritten aio dio correctly

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Date:	Wed, 17 Feb 2016 22:01:48 -0800
From:	Christoph Hellwig <hch@...radead.org>
To:	"Darrick J. Wong" <darrick.wong@...cle.com>
Cc:	Theodore Ts'o <tytso@....edu>,
	linux-ext4 <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH] ext4: use directio end_io error status to finish
 unwritten aio dio correctly

Might help to tell that this is on top of a direct-io.c patch from the
XFS tree.

I don't think clearing any flags is the right thing - now that we
always call ->end_io the code dealing with it in ext4_ext_direct_IO
can simply be moved to the ->end_io handler.

Something like the untested patch below:

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 9db04dd..b741c79 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -3166,23 +3166,25 @@ static int ext4_end_io_dio(struct kiocb *iocb, loff_t offset,
 {
         ext4_io_end_t *io_end = iocb->private;
 
-	if (size <= 0)
-		return 0;
-
 	/* if not async direct IO just return */
 	if (!io_end)
 		return 0;
 
+	if (size <= 0) {
+		WARN_ON(io_end->flag & EXT4_IO_END_UNWRITTEN);
+		goto out;
+	}
+
 	ext_debug("ext4_end_io_dio(): io_end 0x%p "
 		  "for inode %lu, iocb 0x%p, offset %llu, size %zd\n",
  		  iocb->private, io_end->inode->i_ino, iocb, offset,
 		  size);
 
-	iocb->private = NULL;
 	io_end->offset = offset;
 	io_end->size = size;
+out:
 	ext4_put_io_end(io_end);
-
+	iocb->private = NULL;
 	return 0;
 }
 
@@ -3306,16 +3308,6 @@ static ssize_t ext4_ext_direct_IO(struct kiocb *iocb, struct iov_iter *iter,
 	if (io_end) {
 		ext4_inode_aio_set(inode, NULL);
 		ext4_put_io_end(io_end);
-		/*
-		 * When no IO was submitted ext4_end_io_dio() was not
-		 * called so we have to put iocb's reference.
-		 */
-		if (ret <= 0 && ret != -EIOCBQUEUED && iocb->private) {
-			WARN_ON(iocb->private != io_end);
-			WARN_ON(io_end->flag & EXT4_IO_END_UNWRITTEN);
-			ext4_put_io_end(io_end);
-			iocb->private = NULL;
-		}
 	}
 	if (ret > 0 && !overwrite && ext4_test_inode_state(inode,
 						EXT4_STATE_DIO_UNWRITTEN)) {
--
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