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A mirror of the official Linux kernel repository just in case
494c1dfe85
There are currently two problems in the way the objcg pointer array (memcg_data) in the page structure is being allocated and freed. On its allocation, it is possible that the allocated objcg pointer array comes from the same slab that requires memory accounting. If this happens, the slab will never become empty again as there is at least one object left (the obj_cgroup array) in the slab. When it is freed, the objcg pointer array object may be the last one in its slab and hence causes kfree() to be called again. With the right workload, the slab cache may be set up in a way that allows the recursive kfree() calling loop to nest deep enough to cause a kernel stack overflow and panic the system. One way to solve this problem is to split the kmalloc-<n> caches (KMALLOC_NORMAL) into two separate sets - a new set of kmalloc-<n> (KMALLOC_NORMAL) caches for unaccounted objects only and a new set of kmalloc-cg-<n> (KMALLOC_CGROUP) caches for accounted objects only. All the other caches can still allow a mix of accounted and unaccounted objects. With this change, all the objcg pointer array objects will come from KMALLOC_NORMAL caches which won't have their objcg pointer arrays. So both the recursive kfree() problem and non-freeable slab problem are gone. Since both the KMALLOC_NORMAL and KMALLOC_CGROUP caches no longer have mixed accounted and unaccounted objects, this will slightly reduce the number of objcg pointer arrays that need to be allocated and save a bit of memory. On the other hand, creating a new set of kmalloc caches does have the effect of reducing cache utilization. So it is properly a wash. The new KMALLOC_CGROUP is added between KMALLOC_NORMAL and KMALLOC_RECLAIM so that the first for loop in create_kmalloc_caches() will include the newly added caches without change. [vbabka@suse.cz: don't create kmalloc-cg caches with cgroup.memory=nokmem] Link: https://lkml.kernel.org/r/20210512145107.6208-1-longman@redhat.com [akpm@linux-foundation.org: un-fat-finger v5 delta creation] [longman@redhat.com: disable cache merging for KMALLOC_NORMAL caches] Link: https://lkml.kernel.org/r/20210505200610.13943-4-longman@redhat.com Link: https://lkml.kernel.org/r/20210512145107.6208-1-longman@redhat.com Link: https://lkml.kernel.org/r/20210505200610.13943-3-longman@redhat.com Signed-off-by: Waiman Long <longman@redhat.com> Signed-off-by: Vlastimil Babka <vbabka@suse.cz> Suggested-by: Vlastimil Babka <vbabka@suse.cz> Reviewed-by: Shakeel Butt <shakeelb@google.com> Acked-by: Roman Gushchin <guro@fb.com> Cc: Christoph Lameter <cl@linux.com> Cc: David Rientjes <rientjes@google.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: Michal Hocko <mhocko@kernel.org> Cc: Pekka Enberg <penberg@kernel.org> Cc: Vladimir Davydov <vdavydov.dev@gmail.com> [longman@redhat.com: fix for CONFIG_ZONE_DMA=n] Suggested-by: Roman Gushchin <guro@fb.com> Reviewed-by: Vlastimil Babka <vbabka@suse.cz> Cc: Vladimir Davydov <vdavydov.dev@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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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 | ||
| 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.