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5dd9488ae4
commit f66ee0410b1c3481ee75e5db9b34547b4d582465 upstream.
In the case of huge hash:* types of sets, due to the single spinlock of
a set the processing of the whole set under spinlock protection could take
too long.
There were four places where the whole hash table of the set was processed
from bucket to bucket under holding the spinlock:
- During resizing a set, the original set was locked to exclude kernel side
add/del element operations (userspace add/del is excluded by the
nfnetlink mutex). The original set is actually just read during the
resize, so the spinlocking is replaced with rcu locking of regions.
However, thus there can be parallel kernel side add/del of entries.
In order not to loose those operations a backlog is added and replayed
after the successful resize.
- Garbage collection of timed out entries was also protected by the spinlock.
In order not to lock too long, region locking is introduced and a single
region is processed in one gc go. Also, the simple timer based gc running
is replaced with a workqueue based solution. The internal book-keeping
(number of elements, size of extensions) is moved to region level due to
the region locking.
- Adding elements: when the max number of the elements is reached, the gc
was called to evict the timed out entries. The new approach is that the gc
is called just for the matching region, assuming that if the region
(proportionally) seems to be full, then the whole set does. We could scan
the other regions to check every entry under rcu locking, but for huge
sets it'd mean a slowdown at adding elements.
- Listing the set header data: when the set was defined with timeout
support, the garbage collector was called to clean up timed out entries
to get the correct element numbers and set size values. Now the set is
scanned to check non-timed out entries, without actually calling the gc
for the whole set.
Thanks to Florian Westphal for helping me to solve the SOFTIRQ-safe ->
SOFTIRQ-unsafe lock order issues during working on the patch.
Reported-by: syzbot+4b0e9d4ff3cf117837e5@syzkaller.appspotmail.com
Reported-by: syzbot+c27b8d5010f45c666ed1@syzkaller.appspotmail.com
Reported-by: syzbot+68a806795ac89df3aa1c@syzkaller.appspotmail.com
Fixes:
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| 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 | ||
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| MAINTAINERS | ||
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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.