From 195a56986c50599e5d10a558c12f74266fd51bab Mon Sep 17 00:00:00 2001 From: Breno Leitao Date: Fri, 26 Jul 2024 05:09:30 -0700 Subject: [PATCH] docs: fault-injection: document cache-filter feature for failslab The failslab fault injection mechanism has an undocumented capability that provides significant utility in testing and debugging. This feature, introduced in commit 4c13dd3b48fcb ("failslab: add ability to filter slab caches"), allows for targeted error injection into specific slab caches. However, it was inadvertently left undocumented at the time of its implementation. Add documentation for the cache-filter feature in the failslab mode description. Also, providing a practical example demonstrating how to use cache-filter to inject failures specifically when allocating socket buffers (skbs). Signed-off-by: Breno Leitao Reviewed-by: Akinobu Mita Signed-off-by: Jonathan Corbet Link: https://lore.kernel.org/r/20240726120930.3231333-1-leitao@debian.org --- .../fault-injection/fault-injection.rst | 20 +++++++++++++++++++ 1 file changed, 20 insertions(+) diff --git a/Documentation/fault-injection/fault-injection.rst b/Documentation/fault-injection/fault-injection.rst index 70380a2a01b45..07c24710bd214 100644 --- a/Documentation/fault-injection/fault-injection.rst +++ b/Documentation/fault-injection/fault-injection.rst @@ -141,6 +141,14 @@ configuration of fault-injection capabilities. default is 'Y', setting it to 'N' will also inject failures into highmem/user allocations (__GFP_HIGHMEM allocations). +- /sys/kernel/debug/failslab/cache-filter + Format: { 'Y' | 'N' } + + default is 'N', setting it to 'Y' will only inject failures when + objects are requests from certain caches. + + Select the cache by writing '1' to /sys/kernel/slab//failslab: + - /sys/kernel/debug/failslab/ignore-gfp-wait: - /sys/kernel/debug/fail_page_alloc/ignore-gfp-wait: @@ -459,6 +467,18 @@ Application Examples losetup -d $DEVICE rm testfile.img +------------------------------------------------------------------------------ + +- Inject only skbuff allocation failures :: + + # mark skbuff_head_cache as faulty + echo 1 > /sys/kernel/slab/skbuff_head_cache/failslab + # Turn on cache filter (off by default) + echo 1 > /sys/kernel/debug/failslab/cache-filter + # Turn on fault injection + echo 1 > /sys/kernel/debug/failslab/times + echo 1 > /sys/kernel/debug/failslab/probability + Tool to run command with failslab or fail_page_alloc ---------------------------------------------------- -- 2.50.1