Commit 8cdc4d27 authored by David Hildenbrand's avatar David Hildenbrand Committed by Andrew Morton
Browse files

mm/huge_memory: respect MADV_COLLAPSE with PR_THP_DISABLE_EXCEPT_ADVISED 

Let's allow for making MADV_COLLAPSE succeed on areas that neither have
VM_HUGEPAGE nor VM_NOHUGEPAGE when we have THP disabled unless explicitly
advised (PR_THP_DISABLE_EXCEPT_ADVISED).

MADV_COLLAPSE is a clear advice that we want to collapse.

Note that we still respect the VM_NOHUGEPAGE flag, just like
MADV_COLLAPSE always does. So consequently, MADV_COLLAPSE is now only
refused on VM_NOHUGEPAGE with PR_THP_DISABLE_EXCEPT_ADVISED,
including for shmem.

Link: https://lkml.kernel.org/r/20250815135549.130506-4-usamaarif642@gmail.com


Co-developed-by: default avatarUsama Arif <usamaarif642@gmail.com>
Signed-off-by: default avatarUsama Arif <usamaarif642@gmail.com>
Signed-off-by: default avatarDavid Hildenbrand <david@redhat.com>
Reviewed-by: default avatarBaolin Wang <baolin.wang@linux.alibaba.com>
Reviewed-by: default avatarLorenzo Stoakes <lorenzo.stoakes@oracle.com>
Reviewed-by: default avatarZi Yan <ziy@nvidia.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Barry Song <baohua@kernel.org>
Cc: Dev Jain <dev.jain@arm.com>
Cc: Jann Horn <jannh@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Mariano Pache <npache@redhat.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Rik van Riel <riel@surriel.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: SeongJae Park <sj@kernel.org>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Yafang <laoar.shao@gmail.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 1f1c0610

include/linux/huge_mm.h

+7 −1
Original line number Diff line number Diff line
@@ -329,7 +329,7 @@ struct thpsize { 
 * through madvise or prctl.

 */

static inline bool vma_thp_disabled(struct vm_area_struct *vma,

		vm_flags_t vm_flags)

		vm_flags_t vm_flags, bool forced_collapse)

{

	/* Are THPs disabled for this VMA? */

	if (vm_flags & VM_NOHUGEPAGE)
@@ -343,6 +343,12 @@ static inline bool vma_thp_disabled(struct vm_area_struct *vma, 
	 */

	if (vm_flags & VM_HUGEPAGE)

		return false;

	/*

	 * Forcing a collapse (e.g., madv_collapse), is a clear advice to

	 * use THPs.

	 */

	if (forced_collapse)

		return false;

	return mm_flags_test(MMF_DISABLE_THP_EXCEPT_ADVISED, vma->vm_mm);

}

include/uapi/linux/prctl.h

+1 −1
Original line number Diff line number Diff line
@@ -185,7 +185,7 @@ struct prctl_mm_map { 
#define PR_SET_THP_DISABLE	41

/*

 * Don't disable THPs when explicitly advised (e.g., MADV_HUGEPAGE /

 * VM_HUGEPAGE).

 * VM_HUGEPAGE, MADV_COLLAPSE).

 */

# define PR_THP_DISABLE_EXCEPT_ADVISED	(1 << 1)

#define PR_GET_THP_DISABLE	42

mm/huge_memory.c

+3 −2
Original line number Diff line number Diff line
@@ -104,7 +104,8 @@ unsigned long __thp_vma_allowable_orders(struct vm_area_struct *vma, 
{

	const bool smaps = type == TVA_SMAPS;

	const bool in_pf = type == TVA_PAGEFAULT;

	const bool enforce_sysfs = type != TVA_FORCED_COLLAPSE;

	const bool forced_collapse = type == TVA_FORCED_COLLAPSE;

	const bool enforce_sysfs = !forced_collapse;

	unsigned long supported_orders;



	/* Check the intersection of requested and supported orders. */
@@ -122,7 +123,7 @@ unsigned long __thp_vma_allowable_orders(struct vm_area_struct *vma, 
	if (!vma->vm_mm)		/* vdso */

		return 0;



	if (thp_disabled_by_hw() || vma_thp_disabled(vma, vm_flags))

	if (thp_disabled_by_hw() || vma_thp_disabled(vma, vm_flags, forced_collapse))

		return 0;



	/* khugepaged doesn't collapse DAX vma, but page fault is fine. */

mm/memory.c

+4 −2
Original line number Diff line number Diff line
@@ -5332,9 +5332,11 @@ vm_fault_t do_set_pmd(struct vm_fault *vmf, struct folio *folio, struct page *pa 
	 * It is too late to allocate a small folio, we already have a large

	 * folio in the pagecache: especially s390 KVM cannot tolerate any

	 * PMD mappings, but PTE-mapped THP are fine. So let's simply refuse any

	 * PMD mappings if THPs are disabled.

	 * PMD mappings if THPs are disabled. As we already have a THP,

	 * behave as if we are forcing a collapse.

	 */

	if (thp_disabled_by_hw() || vma_thp_disabled(vma, vma->vm_flags))

	if (thp_disabled_by_hw() || vma_thp_disabled(vma, vma->vm_flags,

						     /* forced_collapse=*/ true))

		return ret;



	if (!thp_vma_suitable_order(vma, haddr, PMD_ORDER))

mm/shmem.c

+1 −1
Original line number Diff line number Diff line
@@ -1817,7 +1817,7 @@ unsigned long shmem_allowable_huge_orders(struct inode *inode, 
	vm_flags_t vm_flags = vma ? vma->vm_flags : 0;

	unsigned int global_orders;



	if (thp_disabled_by_hw() || (vma && vma_thp_disabled(vma, vm_flags)))

	if (thp_disabled_by_hw() || (vma && vma_thp_disabled(vma, vm_flags, shmem_huge_force)))

		return 0;



	global_orders = shmem_huge_global_enabled(inode, index, write_end,