[PATCH 1/3] direct-io: add flag to allow aio writes beyond i_size

Christoph Hellwig
2014-02-04T17:25:22Z

[-- Attachment #1: 0001-direct-io-add-flag-to-allow-aio-writes-beyond-i_size.patch --]
[-- Type: text/plain, Size: 1822 bytes --]

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>
---
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 0e04142..11882e8 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 121f11f..f8416fd 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2526,6 +2526,9 @@ 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);
--
1.7.10.4