Commit 74cedf9b authored by Jan Kara's avatar Jan Kara Committed by Jens Axboe

direct-io: Fix negative return from dio read beyond eof

Assume a filesystem with 4KB blocks. When a file has size 1000 bytes and
we issue direct IO read at offset 1024, blockdev_direct_IO() reads the
tail of the last block and the logic for handling short DIO reads in
dio_complete() results in a return value -24 (1000 - 1024) which
obviously confuses userspace.

Fix the problem by bailing out early once we sample i_size and can
reliably check that direct IO read starts beyond i_size.
Reported-by: default avatarAvi Kivity <>
Fixes: 9fe55eea
CC: Steven Whitehouse <>
Signed-off-by: default avatarJan Kara <>
Signed-off-by: default avatarJens Axboe <>
parent bf4e6b4e
......@@ -1169,6 +1169,15 @@ do_blockdev_direct_IO(struct kiocb *iocb, struct inode *inode,
/* Once we sampled i_size check for reads beyond EOF */
dio->i_size = i_size_read(inode);
if (iov_iter_rw(iter) == READ && offset >= dio->i_size) {
if (dio->flags & DIO_LOCKING)
kmem_cache_free(dio_cache, dio);
goto out;
* For file extending writes updating i_size before data writeouts
* complete can expose uninitialized blocks in dumb filesystems.
......@@ -1222,7 +1231,6 @@ do_blockdev_direct_IO(struct kiocb *iocb, struct inode *inode,
sdio.next_block_for_io = -1;
dio->iocb = iocb;
dio->i_size = i_size_read(inode);
dio->refcount = 1;
Markdown is supported
0% or .
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment