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Main-line Linux kernel tree http://www.kernel.org
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Kemeng Shi b5fcf7871a sbitmap: correct wake_batch recalculation to avoid potential IO hung 
Commit 180dccb0db ("blk-mq: fix tag_get wait task can't be awakened")
mentioned that in case of shared tags, there could be just one real
active hctx(queue) because of lazy detection of tag idle. Then driver tag
allocation may wait forever on this real active hctx(queue) if wake_batch
is > hctx_max_depth where hctx_max_depth is available tags depth for the
actve hctx(queue). However, the condition wake_batch > hctx_max_depth is
not strong enough to avoid IO hung as the sbitmap_queue_wake_up will only
wake up one wait queue for each wake_batch even though there is only one
waiter in the woken wait queue. After this, there is only one tag to free
and wake_batch may not be reached anymore. Commit 180dccb0db ("blk-mq:
fix tag_get wait task can't be awakened") methioned that driver tag
allocation may wait forever. Actually, the inactive hctx(queue) will be
truely idle after at most 30 seconds and will call blk_mq_tag_wakeup_all
to wake one waiter per wait queue to break the hung. But IO hung for 30
seconds is also not acceptable. Set batch size to small enough that depth
of the shared hctx(queue) is enough to wake up all of the queues like
sbq_calc_wake_batch do to fix this potential IO hung.

Although hctx_max_depth will be clamped to at least 4 while wake_batch
recalculation does not do the clamp, the wake_batch will be always
recalculated to 1 when hctx_max_depth <= 4.

Fixes: 180dccb0db ("blk-mq: fix tag_get wait task can't be awakened")
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com>
Link: https://lore.kernel.org/r/20230116205059.3821738-6-shikemeng@huaweicloud.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2023-01-29 20:03:01 -07:00
arch - Start checking for -mindirect-branch-cs-prefix clang support too now that LLVM 2023-01-29 11:17:34 -08:00
block blk-cgroup: synchronize pd_free_fn() from blkg_free_workfn() and blkcg_deactivate_policy() 2023-01-29 15:19:04 -07:00
certs
crypto
Documentation block: ublk: fix doc build warning 2023-01-29 15:18:34 -07:00
drivers s390/dcssblk:: don't call bio_split_to_limits 2023-01-29 15:18:35 -07:00
fs 4 smb3 server fixes, all also for stable 2023-01-28 10:52:51 -08:00
include blk-cgroup: synchronize pd_free_fn() from blkg_free_workfn() and blkcg_deactivate_policy() 2023-01-29 15:19:04 -07:00
init
io_uring io_uring: always prep_async for drain requests 2023-01-27 06:29:29 -07:00
ipc
kernel - Cleanup the firmware node for the new IRQ MSI domain properly, to 2023-01-29 11:26:49 -08:00
lib sbitmap: correct wake_batch recalculation to avoid potential IO hung 2023-01-29 20:03:01 -07:00
LICENSES
mm Revert "mm/compaction: fix set skip in fast_find_migrateblock" 2023-01-29 10:38:43 -08:00
net net: mctp: mark socks as dead on unhash, prevent re-add 2023-01-25 13:07:37 +00:00
rust
samples ftrace: Export ftrace_free_filter() to modules 2023-01-24 11:20:58 -05:00
scripts Fix up more non-executable files marked executable 2023-01-28 11:17:57 -08:00
security
sound treewide: fix up files incorrectly marked executable 2023-01-26 10:05:39 -08:00
tools gpio fixes for v6.2-rc6 2023-01-27 13:47:40 -08:00
usr
virt
.clang-format
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore
.mailmap
.rustfmt.toml
COPYING
CREDITS
Kbuild
Kconfig
MAINTAINERS MAINTAINERS: add drbd headers 2023-01-29 15:18:33 -07:00
Makefile Linux 6.2-rc6 2023-01-29 13:59:43 -08:00
README

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.