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4fe2c96315
To support the link with drain, we need to do two parts.
There is an sqes:
0 1 2 3 4 5 6
+-----+-----+-----+-----+-----+-----+-----+
| N | L | L | L+D | N | N | N |
+-----+-----+-----+-----+-----+-----+-----+
First, we need to ensure that the io before the link is completed,
there is a easy way is set drain flag to the link list's head, so
all subsequent io will be inserted into the defer_list.
+-----+
(0) | N |
+-----+
| (2) (3) (4)
+-----+ +-----+ +-----+ +-----+
(1) | L+D | --> | L | --> | L+D | --> | N |
+-----+ +-----+ +-----+ +-----+
|
+-----+
(5) | N |
+-----+
|
+-----+
(6) | N |
+-----+
Second, ensure that the following IO will not be completed first,
an easy way is to create a mirror of drain io and insert it into
defer_list, in this way, as long as drain io is not processed, the
following io in the defer_list will not be actively process.
+-----+
(0) | N |
+-----+
| (2) (3) (4)
+-----+ +-----+ +-----+ +-----+
(1) | L+D | --> | L | --> | L+D | --> | N |
+-----+ +-----+ +-----+ +-----+
|
+-----+
('3) | D | <== This is a shadow of (3)
+-----+
|
+-----+
(5) | N |
+-----+
|
+-----+
(6) | N |
+-----+
Signed-off-by: Jackie Liu <liuyun01@kylinos.cn>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.