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2020-12-15mm: slab: provide krealloc_array()Bartosz Golaszewski
When allocating an array of elements, users should check for multiplication overflow or preferably use one of the provided helpers like: kmalloc_array(). There's no krealloc_array() counterpart but there are many users who use regular krealloc() to reallocate arrays. Let's provide an actual krealloc_array() implementation. While at it: add some documentation regarding krealloc. Link: https://lkml.kernel.org/r/20201109110654.12547-3-brgl@bgdev.pl Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com> Acked-by: Vlastimil Babka <vbabka@suse.cz> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com> Cc: Borislav Petkov <bp@alien8.de> Cc: Borislav Petkov <bp@suse.de> Cc: Christian Knig <christian.koenig@amd.com> Cc: Christoph Lameter <cl@linux.com> Cc: Daniel Vetter <daniel@ffwll.ch> Cc: Daniel Vetter <daniel.vetter@ffwll.ch> Cc: David Airlie <airlied@linux.ie> Cc: David Rientjes <rientjes@google.com> Cc: Gustavo Padovan <gustavo@padovan.org> Cc: James Morse <james.morse@arm.com> Cc: Jaroslav Kysela <perex@perex.cz> Cc: Jason Wang <jasowang@redhat.com> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: Linus Walleij <linus.walleij@linaro.org> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com> Cc: Mauro Carvalho Chehab <mchehab@kernel.org> Cc: Maxime Ripard <mripard@kernel.org> Cc: "Michael S . Tsirkin" <mst@redhat.com> Cc: Pekka Enberg <penberg@kernel.org> Cc: Robert Richter <rric@kernel.org> Cc: Sumit Semwal <sumit.semwal@linaro.org> Cc: Takashi Iwai <tiwai@suse.com> Cc: Takashi Iwai <tiwai@suse.de> Cc: Thomas Zimmermann <tzimmermann@suse.de> Cc: Tony Luck <tony.luck@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-07-23docs/core-api: memory-allocation: describe reclaim behaviourMike Rapoport
Changelog of commit dcda9b04713c ("mm, tree wide: replace __GFP_REPEAT by __GFP_RETRY_MAYFAIL with more useful semantic") has very nice description of GFP flags that affect reclaim behaviour of the page allocator. It would be pity to keep this description buried in the log so let's expose it in the Documentation/ as well. Cc: Michal Hocko <mhocko@suse.com> Acked-by: Michal Hocko <mhocko@suse.com> Signed-off-by: Mike Rapoport <rppt@linux.ibm.com> Link: https://lore.kernel.org/r/20200719153641.231131-1-rppt@kernel.org Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2019-10-29docs/core-api: memory-allocation: mention size helpersChris Packham
Mention struct_size(), array_size() and array3_size() in the same place as kmalloc() and friends. Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz> Acked-by: Mike Rapoport <rppt@linux.ibm.com> Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2019-10-29docs/core-api: memory-allocation: remove uses of c:func:Chris Packham
These are no longer needed as the documentation build will automatically add the cross references. Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz> Acked-by: Mike Rapoport <rppt@linux.ibm.com> Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2019-10-29docs/core-api: memory-allocation: fix typoChris Packham
"on the safe size" should be "on the safe side". Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz> Acked-by: Mike Rapoport <rppt@linux.ibm.com> Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2019-10-07mm, sl[aou]b: guarantee natural alignment for kmalloc(power-of-two)Vlastimil Babka
In most configurations, kmalloc() happens to return naturally aligned (i.e. aligned to the block size itself) blocks for power of two sizes. That means some kmalloc() users might unknowingly rely on that alignment, until stuff breaks when the kernel is built with e.g. CONFIG_SLUB_DEBUG or CONFIG_SLOB, and blocks stop being aligned. Then developers have to devise workaround such as own kmem caches with specified alignment [1], which is not always practical, as recently evidenced in [2]. The topic has been discussed at LSF/MM 2019 [3]. Adding a 'kmalloc_aligned()' variant would not help with code unknowingly relying on the implicit alignment. For slab implementations it would either require creating more kmalloc caches, or allocate a larger size and only give back part of it. That would be wasteful, especially with a generic alignment parameter (in contrast with a fixed alignment to size). Ideally we should provide to mm users what they need without difficult workarounds or own reimplementations, so let's make the kmalloc() alignment to size explicitly guaranteed for power-of-two sizes under all configurations. What this means for the three available allocators? * SLAB object layout happens to be mostly unchanged by the patch. The implicitly provided alignment could be compromised with CONFIG_DEBUG_SLAB due to redzoning, however SLAB disables redzoning for caches with alignment larger than unsigned long long. Practically on at least x86 this includes kmalloc caches as they use cache line alignment, which is larger than that. Still, this patch ensures alignment on all arches and cache sizes. * SLUB layout is also unchanged unless redzoning is enabled through CONFIG_SLUB_DEBUG and boot parameter for the particular kmalloc cache. With this patch, explicit alignment is guaranteed with redzoning as well. This will result in more memory being wasted, but that should be acceptable in a debugging scenario. * SLOB has no implicit alignment so this patch adds it explicitly for kmalloc(). The potential downside is increased fragmentation. While pathological allocation scenarios are certainly possible, in my testing, after booting a x86_64 kernel+userspace with virtme, around 16MB memory was consumed by slab pages both before and after the patch, with difference in the noise. [1] https://lore.kernel.org/linux-btrfs/c3157c8e8e0e7588312b40c853f65c02fe6c957a.1566399731.git.christophe.leroy@c-s.fr/ [2] https://lore.kernel.org/linux-fsdevel/20190225040904.5557-1-ming.lei@redhat.com/ [3] https://lwn.net/Articles/787740/ [akpm@linux-foundation.org: documentation fixlet, per Matthew] Link: http://lkml.kernel.org/r/20190826111627.7505-3-vbabka@suse.cz Signed-off-by: Vlastimil Babka <vbabka@suse.cz> Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org> Acked-by: Michal Hocko <mhocko@suse.com> Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Acked-by: Christoph Hellwig <hch@lst.de> Cc: David Sterba <dsterba@suse.cz> Cc: Christoph Lameter <cl@linux.com> Cc: Pekka Enberg <penberg@kernel.org> Cc: David Rientjes <rientjes@google.com> Cc: Ming Lei <ming.lei@redhat.com> Cc: Dave Chinner <david@fromorbit.com> Cc: "Darrick J . Wong" <darrick.wong@oracle.com> Cc: Christoph Hellwig <hch@lst.de> Cc: James Bottomley <James.Bottomley@HansenPartnership.com> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2019-02-01docs: Use underscore not hyphen in labelTobin C. Harding
sphinx emits warning WARNING: undefined label: memory-allocation ... This seems to be caused by the use of a hyphen in the label name instead of an underscore. Using an underscore for the label name and the reference clears the warning. Use underscore not hyphen in label and reference. Signed-off-by: Tobin C. Harding <tobin@kernel.org> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2019-01-14docs/core-api: memory-allocation: add mention of kmem_cache_create_userspaceMike Rapoport
Mention that when a part of a slab cache might be exported to the userspace, the cache should be created using kmem_cache_create_usercopy() Signed-off-by: Mike Rapoport <rppt@linux.ibm.com> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2018-11-20Link the memory allocation guide from the MM docsMatthew Wilcox
I just went looking for the memory allocation guide in the MM docs instead of in the core API. For the benefit of the next person who makes that mistake, link to it from the MM docs. Signed-off-by: Matthew Wilcox <willy@infradead.org> Acked-by: Mike Rapoport <rppt@linux.ibm.com> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2018-09-20docs: core-api: add memory allocation guideMike Rapoport
Signed-off-by: Mike Rapoport <rppt@linux.vnet.ibm.com> Acked-by: Michal Hocko <mhocko@suse.com> Acked-by: Randy Dunlap <rdunlap@infradead.org> Signed-off-by: Jonathan Corbet <corbet@lwn.net>