In (060807f841ac mm, slub: make remaining slub_debug related attributes read-only failslab) it was made RO. I think it became a collateral victim to the other two options (sanity_checks and trace) for which the reasons are perfectly valid. Here is why: - sanity_checks and trace are slab internal debug options, failslab is used for fault injection. - for fault injections, which by presumption are random, it does not matter if it is not set atomically. You need to set atleast one more option to trigger fault injection. - in a testing scenario you may need to change it at runtime example: module loading - you test all allocations limited by the space option. Then you move to test only your module's own slabs. - when set by command line flags it effectively disables all cache merges. Cc: Vlastimil Babka <vbabka@xxxxxxx> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Cc: Kees Cook <keescook@xxxxxxxxxxxx> Cc: Roman Gushchin <guro@xxxxxx> Cc: Christoph Lameter <cl@xxxxxxxxx> Cc: Jann Horn <jannh@xxxxxxxxxx> Cc: Vijayanand Jitta <vjitta@xxxxxxxxxxxxxx> Cc: David Rientjes <rientjes@xxxxxxxxxx> Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx> Cc: Pekka Enberg <penberg@xxxxxxxxxx> Link: http://lkml.kernel.org/r/20200610163135.17364-5-vbabka@xxxxxxx Signed-off-by: Alexander Atanasov <alexander.atanasov@xxxxxxxxxxxxx> --- Documentation/mm/slub.rst | 2 ++ mm/slub.c | 14 +++++++++++++- 2 files changed, 15 insertions(+), 1 deletion(-) diff --git a/Documentation/mm/slub.rst b/Documentation/mm/slub.rst index 43063ade737a..86837073a39e 100644 --- a/Documentation/mm/slub.rst +++ b/Documentation/mm/slub.rst @@ -116,6 +116,8 @@ options from the ``slub_debug`` parameter translate to the following files:: T trace A failslab +failslab file is writable, so writing 1 or 0 will enable or disable +the option at runtime. Write returns -EINVAL if cache is an alias. Careful with tracing: It may spew out lots of information and never stop if used on the wrong slab. diff --git a/mm/slub.c b/mm/slub.c index 862dbd9af4f5..7c15d312e0fb 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -5617,7 +5617,19 @@ static ssize_t failslab_show(struct kmem_cache *s, char *buf) { return sysfs_emit(buf, "%d\n", !!(s->flags & SLAB_FAILSLAB)); } -SLAB_ATTR_RO(failslab); + +static ssize_t failslab_store(struct kmem_cache *s, const char *buf, + size_t length) +{ + if (s->refcount > 1) + return -EINVAL; + + s->flags &= ~SLAB_FAILSLAB; + if (buf[0] == '1') + s->flags |= SLAB_FAILSLAB; + return length; +} +SLAB_ATTR(failslab); #endif static ssize_t shrink_show(struct kmem_cache *s, char *buf) base-commit: 80e78fcce86de0288793a0ef0f6acf37656ee4cf -- 2.31.1
