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For !CONFIG_TRACING kernels, the kmalloc() implementation tries (in cases where
the allocation size is build-time constant) to save a function call, by
inlining kmalloc_trace() to a kmem_cache_alloc() call.
However since commit 6edf2576a6 ("mm/slub: enable debugging memory wasting of
kmalloc") this path now fails to pass the original request size to be
eventually recorded (for kmalloc caches with debugging enabled).
We could adjust the code to call __kmem_cache_alloc_node() as the
CONFIG_TRACING variant, but that would as a result inline a call with 5
parameters, bloating the kmalloc() call sites. The cost of extra function
call (to kmalloc_trace()) seems like a lesser evil.
It also appears that the !CONFIG_TRACING variant is incompatible with upcoming
hardening efforts [1] so it's easier if we just remove it now. Kernels with no
tracing are rare these days and the benefit is dubious anyway.
[1] https://lore.kernel.org/linux-mm/20221101222520.never.109-kees@kernel.org/T/#m20ecf14390e406247bde0ea9cce368f469c539ed
Link: https://lore.kernel.org/all/097d8fba-bd10-a312-24a3-a4068c4f424c@suse.cz/
Suggested-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
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.