The following is a fix to the patch mm-thp-set-thp-defrag-by-default-to-madvise-and-add-a-stall-free-defrag-option.patch based on feedback from Vlastimil Babka. It removes an unnecessary VM_BUG_ON for tidyness, clarifies documentation and adds a check forbidding someone writing "defer" to the enable knob for transparent huge pages. The ack from Vlastimil applies for the original patch plus this fix combined.
Signed-off-by: Mel Gorman <[email protected]> Acked-by: Vlastimil Babka <[email protected]> --- Documentation/vm/transhuge.txt | 2 +- mm/huge_memory.c | 7 ++++--- 2 files changed, 5 insertions(+), 4 deletions(-) diff --git a/Documentation/vm/transhuge.txt b/Documentation/vm/transhuge.txt index a19b173cbc57..1943fe051a36 100644 --- a/Documentation/vm/transhuge.txt +++ b/Documentation/vm/transhuge.txt @@ -129,7 +129,7 @@ available in the near future. It's the responsibility of khugepaged to then install the THP pages later. "madvise" will enter direct reclaim like "always" but only for regions -that are have used madvise(). This is the default behaviour. +that are have used madvise(MADV_HUGEPAGE). This is the default behaviour. "never" should be self-explanatory. diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 206f35f06d83..9161b3a83720 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -246,6 +246,8 @@ static ssize_t triple_flag_store(struct kobject *kobj, { if (!memcmp("defer", buf, min(sizeof("defer")-1, count))) { + if (enabled == deferred) + return -EINVAL; clear_bit(enabled, &transparent_hugepage_flags); clear_bit(req_madv, &transparent_hugepage_flags); set_bit(deferred, &transparent_hugepage_flags); @@ -273,10 +275,9 @@ static ssize_t triple_flag_store(struct kobject *kobj, static ssize_t enabled_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf) { - if (test_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags)) { - VM_BUG_ON(test_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags)); + if (test_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags)) return sprintf(buf, "[always] madvise never\n"); - } else if (test_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags)) + else if (test_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags)) return sprintf(buf, "always [madvise] never\n"); else return sprintf(buf, "always madvise [never]\n");
