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5291984004
Expanded testing of DM's bio polling support (using more fio threads
to dm-linear ontop of null_blk) exposed the possibility for polled
bios to hang (repeatedly polling in io_uring) when null_blk responds
with BLK_STS_AGAIN (due to lack of resources):
1) io_complete_rw_iopoll() is called from blkdev_bio_end_io_async() to
notify kiocb is done, that is the completion interface between block
layer and io_uring
2) io_complete_rw_iopoll() is called from io_do_iopoll()
3) dm returns BLK_STS_AGAIN for one bio (on behalf of underlying
driver), then io_complete_rw_iopoll is called, but io_do_iopoll()
doesn't handle -EAGAIN at all (due to logic in io_rw_should_reissue)
4) reason for dm's BLK_STS_AGAIN is underlying null_blk driver ran out
of requests (easier to reproduce by setting low hw_queue_depth).
5) dm should handle BLK_STS_AGAIN for POLLED underlying IO, and may
retry in dm layer.
This fix adds REQ_POLLED specific BLK_STS_AGAIN handling to
dm_io_complete() that clears REQ_POLLED and requeues the bio to DM
using queue_io().
Fixes:
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|---|---|---|
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| 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.