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Howlett" , Nico Pache , Ryan Roberts , Barry Song , Lance Yang , Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20260511025408.54035-1-ye.liu@linux.dev> Content-Language: en-US From: Dev Jain In-Reply-To: <20260511025408.54035-1-ye.liu@linux.dev> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 7AD01180004 X-Stat-Signature: e894p9i66jogdas9hkj1xm3fm49mgqdd X-HE-Tag: 1778478351-109942 X-HE-Meta: U2FsdGVkX1/+y98V0R0RsQF0UoNKVORMZKcR57kC9UaeW64ezC0B6DNVwu7t71LwKfXYwsoH5sm/bpnRE+0Od+SERJY6+MRYXZkKWlb9O9s9pTZk4CAxMX4g646n2KZqI9aP5xaO6/ySHWJkF+tlQ6EJFveZFo/PRiPwWmSKDusX5qX7OXFgvZYIcb83Y/x1/OKcfQrzbYpASmg+sRJ79BvtUsMChbniWHHkjEBJVOhutfE0rxzM4lij1+EAIAo7yswOiZVMtTZ4D5e6CLmNVfZKP2HHd0u/5x8oyC7+jU91AE25GN2x0E3ZjyxuJJUroY2MU2t8nyMLpN4ryZai15ZeL8p6TgTCbCqPTXBLydPoo2eLnDaoghmabCEzwU2XTL5to1ETnstiXtBDZRiNY9OHvidkFhxYwDvLr+rNF1KqwtRAFZ2NHaewbu2v3uDZIlbvFl1eTRHKLsH8sV/hHj5lixG1vf3R2p+4epIKhV7TCBFOfrgVaJYrG34B7+n8LxUgl5zjwpo2EMsOby88V8+QGu8ddpagCR6a7Hkke8tdZEk79VtF6za2XJmuOD2RfoWJg27/fNCi51w30Pxgh+vgVVOhrjkpQaysmnCXhCWu5hF1qcxkXW5LrZxSoL4mKPUSoAyZ4QVqoj2p9tMivxMVAUW+l2lI3NZKZyKCE6BdRfuTX0kCBj2R4kdsi2TDi8qtMGwNKI1WznmAS/6iBP2RfAXa/yPFvxvtvDwkRxjFhMbtx9EQkXHviH5R3unLvC5gZStmfpEUZ6d5DMquwOS8O3z7oC42yGwA6zWPQYfIEF+aTxMeAG/BIUsiptOaozbZyn16fCwac6vwwNbYlv3KOTtsOmi8Pd5AnoAb7l6TKSzftf6tiGrxmq+o2jOzk1Vhn3SrfxAG9h3bnIN0O+mD8JceXtGD80jG9m28sYILGC5tRqhzhUFSFliTfcAMiZWengyrtl0siStV1GK PoZLDmYh V8DHjhEsrJOt+W4C34jTEeyEUIkeHPgg0GafKC3HCQhE7SQfDQaFd3b3dSmJ/qm8+Trcm/wcJx4wEudGqduN1haYfJIGNGn7h+P6x0jLclSndIE36nm3i/5nlnNZMvd0kzbDiHZE3s+70sSH56JpDHw9cWRsaAsdrAkl6kHdJ7aoyS9kv0k0WKXGBP/9nNEPw/JHaR9W7F4GgLwkg+x/X1XDA3aOhGNP3bfPyxCeiOVzGwcYDBOpneHGQ3HmpCLa7LOJ85Jueq5Gd295qzRzngEcOak1sE0ncJQoP6jotKqqDO4goZEuXeQ0mO3uqTOPB7kPEStUk/CbsdcUm6sMyLf2kBKipTt3IXiNb3a/OAi0uJ/E= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 11/05/26 8:24 am, Ye Liu wrote: > From: Ye Liu > > __khugepaged_enter() sets MMF_VM_HUGEPAGE before allocating the > corresponding mm_slot. If mm_slot_alloc() fails, the function > returns with the flag set but without inserting the mm into the > khugepaged tracking structures, leaving the mm in an inconsistent > state where future registration attempts are skipped. > > Fix this by reordering: allocate the mm_slot first, then check and > set the flag. If the flag is already set, free the allocated slot > and return. This ensures the flag is only set when the mm is > successfully registered in the khugepaged tracking structures. > > Fixes: 16618670276a ("mm: khugepaged: avoid pointless allocation for "struct mm_slot"") > Suggested-by: David Hildenbrand > Signed-off-by: Ye Liu > --- Reviewed-by: Dev Jain > Changes since v2: > - Reorder to allocate mm_slot first, free it when flag already set, > as suggested by David, Dev Jain and Lance Yang > - Update the subject line to better match the patch. > - Link: https://lore.kernel.org/all/20260506012130.9306-1-ye.liu@linux.dev/ > > Changes since v1: > - Add Fixes tag as suggested by Dev Jain and Lance Yang > - Link: https://lore.kernel.org/all/20260501075708.327217-1-ye.liu@linux.dev/ > > mm/khugepaged.c | 7 +++++-- > 1 file changed, 5 insertions(+), 2 deletions(-) > > diff --git a/mm/khugepaged.c b/mm/khugepaged.c > index 5f4e009593e0..78735f34250a 100644 > --- a/mm/khugepaged.c > +++ b/mm/khugepaged.c > @@ -437,13 +437,16 @@ void __khugepaged_enter(struct mm_struct *mm) > > /* __khugepaged_exit() must not run from under us */ > VM_BUG_ON_MM(collapse_test_exit(mm), mm); > - if (unlikely(mm_flags_test_and_set(MMF_VM_HUGEPAGE, mm))) > - return; > > slot = mm_slot_alloc(mm_slot_cache); > if (!slot) > return; > > + if (unlikely(mm_flags_test_and_set(MMF_VM_HUGEPAGE, mm))) { > + mm_slot_free(mm_slot_cache, slot); > + return; > + } > + > spin_lock(&khugepaged_mm_lock); > mm_slot_insert(mm_slots_hash, mm, slot); > /*