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Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Vlastimil Babka , Suren Baghdasaryan , Michal Hocko , Brendan Jackman , Johannes Weiner , linux-mm@kvack.org, linux-kernel@vger.kernel.org, usamaarif642@gmail.com, kas@kernel.org, kernel-team@meta.com Subject: Re: [PATCH v2 3/3] mm: huge_memory: refactor enabled_store() with change_enabled() Message-ID: References: <20260305-thp_logs-v2-0-96b3ad795894@debian.org> <20260305-thp_logs-v2-3-96b3ad795894@debian.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260305-thp_logs-v2-3-96b3ad795894@debian.org> X-Rspamd-Queue-Id: 74AA0A000A X-Rspamd-Server: rspam07 X-Stat-Signature: u6xajfqzyupm9j3dz9a7sqjxxpeb77b5 X-Rspam-User: X-HE-Tag: 1772797172-1939 X-HE-Meta: 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 trMulgew IOccxhD3G2r3promSyW/fCT3J8w0X1/d6K7QGZhZY1hlLkPL06wWkdkOLdH33AKXYlSMIqBsZjhbp7PnjQUgswUQltFWzZnYFOr3eg2DGaNKGZGVwB73a/tEObFPt8oe35CL7dLdTJTh3uJOVdk9EB4VzKxyNP1lB3KmFxgYrwC1gIQR5Ix7VxgqSprEn4WiXqDQOiJfKAmXeJYAF0+/8sIw2vVf2UQTBBifZgX7amBj/tiwJhWpCJax8+y1qtO33q5oA8aNPd1LJBk24yqJwnaOZ1X9XxKsZgg3H6BCJhznjQq2MjCrRnjWwMA== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, Mar 05, 2026 at 06:04:55AM -0800, Breno Leitao wrote: > Refactor enabled_store() to use a new change_enabled() helper that > reuses the shared enum enabled_mode and enabled_mode_strings[] > introduced in the previous commit. > > The helper uses the same loop pattern as change_anon_orders(), > iterating over an array of flag bit positions and using > test_and_set_bit()/test_and_clear_bit() to track whether the state > actually changed. ENABLED_INHERIT is rejected since it is not a > valid mode for the global THP setting. > > Signed-off-by: Breno Leitao > --- > mm/huge_memory.c | 51 ++++++++++++++++++++++++++++++++++++--------------- > 1 file changed, 36 insertions(+), 15 deletions(-) > > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > index 19619213f54d1..dd5011cf36839 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -330,30 +330,51 @@ static const char * const enabled_mode_strings[] = { > [ENABLED_NEVER] = "never", > }; > > +static bool change_enabled(enum enabled_mode mode) > +{ > + static const unsigned long thp_flags[] = { > + TRANSPARENT_HUGEPAGE_FLAG, > + TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, > + }; > + bool changed = false; > + int i; > + > + for (i = 0; i < ARRAY_SIZE(thp_flags); i++) { > + if (i == mode) > + changed |= !test_and_set_bit(thp_flags[i], > + &transparent_hugepage_flags); > + else > + changed |= test_and_clear_bit(thp_flags[i], > + &transparent_hugepage_flags); > + } > + > + return changed; > +} > + > static ssize_t enabled_store(struct kobject *kobj, > struct kobj_attribute *attr, > const char *buf, size_t count) > { > - ssize_t ret = count; > + int mode; > > - if (sysfs_streq(buf, "always")) { > - clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags); > - set_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags); > - } else if (sysfs_streq(buf, "madvise")) { > - clear_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags); > - set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags); > - } else if (sysfs_streq(buf, "never")) { > - clear_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags); > - clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags); > - } else > - ret = -EINVAL; > + mode = sysfs_match_string(enabled_mode_strings, buf); > + if (mode < 0 || mode == ENABLED_INHERIT) > + return -EINVAL; The mode == ENABLED_INHERIT check is weird, it reads like 'oh a user CAN specify this, but if they do we error out', but in reality /sys/kernel/mm/transparent_hugepage/enabled explicitly outputs only always, inherit, maddvise. So, even though it's duplicative, I think it's probably saner to have: static const char * const anon_enabled_mode_strings[] = { [ENABLED_ALWAYS] = "always", [ENABLED_MADVISE] = "madvise", [ENABLED_INHERIT] = "inherit", [ENABLED_NEVER] = "never", }; static const char * const global_enabled_mode_strings[] = { [ENABLED_ALWAYS] = "always", [ENABLED_MADVISE] = "madvise", [ENABLED_NEVER] = "never", }; Just to make it clear what you're doing. And if you add something for shmem add one for that too. With that fixed, feel free to add: Reviewed-by: Lorenzo Stoakes (Oracle) > > - if (ret > 0) { > + if (change_enabled(mode)) { > int err = start_stop_khugepaged(); > + > if (err) > - ret = err; > + return err; > + } else { > + /* > + * Recalculate watermarks even when the mode didn't > + * change, as the previous code always called > + * start_stop_khugepaged() which does this internally. > + */ > + set_recommended_min_free_kbytes(); > } > - return ret; > + return count; > } > > static struct kobj_attribute enabled_attr = __ATTR_RW(enabled); > > -- > 2.47.3 > Cheers, Lorenzo