Linux mainline fork with MSM8998 patches | https://mainline.space | Currently supported devices:
OnePlus 5/5T, Xiaomi Mi 6, F(x)tec Pro¹ (2019 QX1000 model) & Sony Xperia XZ Premium (UNTESTED!)
9e23ccf8f0
When there is a lot of data cached on cache device, the bcach internal btree can take a very long to validate during the backing device and cache device registration. In my test, it may takes 55+ minutes to check all the internal btree nodes. The problem is that the registration is invoked by udev rules and the udevd has 180 seconds timeout by default. If the btree node checking time is longer than udevd timeout, the registering process will be killed by udevd with SIGKILL. If the registering process has pending sigal, creating kthread for bcache will fail and the device registration will fail. The result is, for bcache device which cached a lot of data on cache device, the bcache device node like /dev/bcache<N> won't create always due to the very long btree checking time. A solution to avoid the udevd 180 seconds timeout is to register devices in an asynchronous way. Which is, after writing cache or backing device path into /sys/fs/bcache/register_async, the kernel code will create a kworker and move all the btree node checking (for cache device) or dirty data counting (for cached device) in the kwork context. Then the kworder is scheduled on system_wq and the registration code just returned to user space udev rule task. By this asynchronous way, the udev task for bcache rule will complete in seconds, no matter how long time spent in the kworker context, it won't be killed by udevd for a timeout. After all the checking and counting are done asynchronously in the kworker, the bcache device will eventually be created successfully. This patch does the above chagne and add a register sysfs file /sys/fs/bcache/register_async. Writing the registering device path into this sysfs file will do the asynchronous registration. The register_async interface is for very rare condition and won't be used for common users. In future I plan to make the asynchronous registration as default behavior, which depends on feedback for this patch. Signed-off-by: Coly Li <colyli@suse.de> Signed-off-by: Jens Axboe <axboe@kernel.dk> |
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| Documentation | ||
| drivers | ||
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| init | ||
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| .clang-format | ||
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| README | ||
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.