On 29 May 2025, at 4:23, Baolin Wang wrote:
> The MADV_COLLAPSE will ignore the system-wide shmem THP sysfs settings, which
> means that even though we have disabled the shmem THP configuration, MADV_COLLAPSE
> will still attempt to collapse into a shmem THP. This violates the rule we have
> agreed upon: never means never.
>
> Then the current strategy is:
> For shmem, if none of always, madvise, within_size, and inherit have enabled
> PMD-sized mTHP, then MADV_COLLAPSE will be prohibited from collapsing PMD-sized mTHP.
>
> For tmpfs, if the mount option is set with the 'huge=never' parameter, then
> MADV_COLLAPSE will be prohibited from collapsing PMD-sized mTHP.
>
> Signed-off-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>
> ---
> mm/huge_memory.c | 2 +-
> mm/shmem.c | 12 ++++++------
> 2 files changed, 7 insertions(+), 7 deletions(-)
>
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index d3e66136e41a..a8cfa37cae72 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -166,7 +166,7 @@ unsigned long __thp_vma_allowable_orders(struct vm_area_struct *vma,
> * own flags.
> */
> if (!in_pf && shmem_file(vma->vm_file))
> - return shmem_allowable_huge_orders(file_inode(vma->vm_file),
> + return orders & shmem_allowable_huge_orders(file_inode(vma->vm_file),
> vma, vma->vm_pgoff, 0,
> !enforce_sysfs);
OK, here orders is checked against allowed orders.
>
> diff --git a/mm/shmem.c b/mm/shmem.c
> index 4b42419ce6b2..4dbb28d85cd9 100644
> --- a/mm/shmem.c
> +++ b/mm/shmem.c
> @@ -613,7 +613,7 @@ static unsigned int shmem_get_orders_within_size(struct inode *inode,
> }
>
> static unsigned int shmem_huge_global_enabled(struct inode *inode, pgoff_t index,
> - loff_t write_end, bool shmem_huge_force,
> + loff_t write_end,
> struct vm_area_struct *vma,
> unsigned long vm_flags)
> {
> @@ -625,7 +625,7 @@ static unsigned int shmem_huge_global_enabled(struct inode *inode, pgoff_t index
> return 0;
> if (shmem_huge == SHMEM_HUGE_DENY)
> return 0;
> - if (shmem_huge_force || shmem_huge == SHMEM_HUGE_FORCE)
> + if (shmem_huge == SHMEM_HUGE_FORCE)
> return maybe_pmd_order;
shmem_huge is set by sysfs?
>
> /*
> @@ -860,7 +860,7 @@ static unsigned long shmem_unused_huge_shrink(struct shmem_sb_info *sbinfo,
> }
>
> static unsigned int shmem_huge_global_enabled(struct inode *inode, pgoff_t index,
> - loff_t write_end, bool shmem_huge_force,
> + loff_t write_end,
> struct vm_area_struct *vma,
> unsigned long vm_flags)
> {
> @@ -1261,7 +1261,7 @@ static int shmem_getattr(struct mnt_idmap *idmap,
> STATX_ATTR_NODUMP);
> generic_fillattr(idmap, request_mask, inode, stat);
>
> - if (shmem_huge_global_enabled(inode, 0, 0, false, NULL, 0))
> + if (shmem_huge_global_enabled(inode, 0, 0, NULL, 0))
> stat->blksize = HPAGE_PMD_SIZE;
>
> if (request_mask & STATX_BTIME) {
> @@ -1768,7 +1768,7 @@ unsigned long shmem_allowable_huge_orders(struct inode *inode,
> return 0;
>
> global_orders = shmem_huge_global_enabled(inode, index, write_end,
> - shmem_huge_force, vma, vm_flags);
> + vma, vm_flags);
> /* Tmpfs huge pages allocation */
> if (!vma || !vma_is_anon_shmem(vma))
> return global_orders;
> @@ -1790,7 +1790,7 @@ unsigned long shmem_allowable_huge_orders(struct inode *inode,
> /* Allow mTHP that will be fully within i_size. */
> mask |= shmem_get_orders_within_size(inode, within_size_orders, index, 0);
>
> - if (vm_flags & VM_HUGEPAGE)
> + if (shmem_huge_force || (vm_flags & VM_HUGEPAGE))
> mask |= READ_ONCE(huge_shmem_orders_madvise);
>
> if (global_orders > 0)
> --
> 2.43.5
shmem_huge_force comes from !enforce_sysfs in __thp_vma_allowable_orders().
Do you know when sysfs is not enforced and why?
Best Regards,
Yan, Zi
