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mm/huge_memory: respect MADV_COLLAPSE with PR_THP_DISABLE_EXCEPT_ADVISED

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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: Usama Arif <usamaarif642@gmail.com>
Signed-off-by: Usama Arif <usamaarif642@gmail.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Reviewed-by: Zi 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: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
David Hildenbrand
2025-08-15 14:54:55 +01:00
committed by Andrew Morton
parent 1f1c061089
commit 8cdc4d2701
5 changed files with 16 additions and 7 deletions
Download Patch File Download Diff File Expand all files Collapse all files

8
include/linux/huge_mm.h
View File

@@ -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);
}

2
include/uapi/linux/prctl.h
View File

@@ -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

5
mm/huge_memory.c
View File

@@ -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. */

6
mm/memory.c
View File

@@ -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))

2
mm/shmem.c
View File

@@ -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,