block: loop: prepare for supporing direct IO

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This patches provides one interface for enabling direct IO
from user space:

	- userspace(such as losetup) can pass 'file' which is
	opened/fcntl as O_DIRECT

Also __loop_update_dio() is introduced to check if direct I/O
can be used on current loop setting.

The last big change is to introduce LO_FLAGS_DIRECT_IO flag
for userspace to know if direct IO is used to access backing
file.

Cc: linux-api@vger.kernel.org
Signed-off-by: Ming Lei <ming.lei@canonical.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@fb.com>

...

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Ming Lei 2015-08-17 10:31:49 +08:00 • committed by Jens Axboe

parent e03a3d7a94

commit 2e5ab5f379

3 changed files with 79 additions and 0 deletions

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include/uapi/linux/loop.h

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