From 6039257378e4c84da06e68230b14fef955508ce6 Mon Sep 17 00:00:00 2001
From: Christoph Hellwig <hch@infradead.org>
Date: Mon, 10 Feb 2014 10:27:11 +1100
Subject: [PATCH] direct-io: add flag to allow aio writes beyond i_size
Some filesystems can handle direct I/O writes beyond i_size safely,
so allow them to opt into receiving them.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
---
fs/direct-io.c | 18 ++++++++++++------
include/linux/fs.h | 3 +++
2 files changed, 15 insertions(+), 6 deletions(-)
diff --git a/fs/direct-io.c b/fs/direct-io.c
index 160a5489a9393..a701752dd7505 100644
--- a/fs/direct-io.c
+++ b/fs/direct-io.c
@@ -1194,13 +1194,19 @@ do_blockdev_direct_IO(int rw, struct kiocb *iocb, struct inode *inode,
}
/*
- * For file extending writes updating i_size before data
- * writeouts complete can expose uninitialized blocks. So
- * even for AIO, we need to wait for i/o to complete before
- * returning in this case.
+ * For file extending writes updating i_size before data writeouts
+ * complete can expose uninitialized blocks in dumb filesystems.
+ * In that case we need to wait for I/O completion even if asked
+ * for an asynchronous write.
*/
- dio->is_async = !is_sync_kiocb(iocb) && !((rw & WRITE) &&
- (end > i_size_read(inode)));
+ if (is_sync_kiocb(iocb))
+ dio->is_async = false;
+ else if (!(dio->flags & DIO_ASYNC_EXTEND) &&
+ (rw & WRITE) && end > i_size_read(inode))
+ dio->is_async = false;
+ else
+ dio->is_async = true;
+
dio->inode = inode;
dio->rw = rw;
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 09f553c59813a..f7faefcf48435 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2527,6 +2527,9 @@ enum {
/* filesystem does not support filling holes */
DIO_SKIP_HOLES = 0x02,
+
+ /* filesystem can handle aio writes beyond i_size */
+ DIO_ASYNC_EXTEND = 0x04,
};
void dio_end_io(struct bio *bio, int error);
--
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