09c3717c3a
bio_ctrl->len_to_oe_boundary is used to make sure we stay inside a zone as we submit bios for writes. Every time we add a page to the bio, we decrement those bytes from len_to_oe_boundary, and then we submit the bio if we happen to hit zero. Most of the time, len_to_oe_boundary gets set to U32_MAX. submit_extent_page() adds pages into our bio, and the size of the bio ends up limited by: - Are we contiguous on disk? - Does bio_add_page() allow us to stuff more in? - is len_to_oe_boundary > 0? The len_to_oe_boundary math starts with U32_MAX, which isn't page or sector aligned, and subtracts from it until it hits zero. In the non-zoned case, the last IO we submit before we hit zero is going to be unaligned, triggering BUGs. This is hard to trigger because bio_add_page() isn't going to make a bio of U32_MAX size unless you give it a perfect set of pages and fully contiguous extents on disk. We can hit it pretty reliably while making large swapfiles during provisioning because the machine is freshly booted, mostly idle, and the disk is freshly formatted. It's also possible to trigger with reads when read_ahead_kb is set to 4GB. The code has been clean up and shifted around a few times, but this flaw has been lurking since the counter was added. I think the commit |
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| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| io_uring | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| rust | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| .rustfmt.toml | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| 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.