The patch titled Subject: mm/hugetlb: do not call vma_add_reservation upon ENOMEM has been added to the -mm mm-hotfixes-unstable branch. Its filename is mm-hugetlb-do-not-call-vma_add_reservation-upon-enomem.patch
This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches...
This patch will later appear in the mm-hotfixes-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------ From: Oscar Salvador osalvador@suse.de Subject: mm/hugetlb: do not call vma_add_reservation upon ENOMEM Date: Tue, 28 May 2024 22:53:23 +0200
sysbot reported a splat [1] on __unmap_hugepage_range(). This is because vma_needs_reservation() can return -ENOMEM if allocate_file_region_entries() fails to allocate the file_region struct for the reservation.
Check for that and do not call vma_add_reservation() if that is the case, otherwise region_abort() and region_del() will see that we do not have any file_regions.
If we detect that vma_needs_reservation() returned -ENOMEM, we clear the hugetlb_restore_reserve flag as if this reservation was still consumed, so free_huge_folio() will not increment the resv count.
[1] https://lore.kernel.org/linux-mm/0000000000004096100617c58d54@google.com/T/#...
Link: https://lkml.kernel.org/r/20240528205323.20439-1-osalvador@suse.de Fixes: df7a6d1f6405 ("mm/hugetlb: restore the reservation if needed") Signed-off-by: Oscar Salvador osalvador@suse.de Reported-and-tested-by: syzbot+d3fe2dc5ffe9380b714b@syzkaller.appspotmail.com Closes: https://lore.kernel.org/linux-mm/0000000000004096100617c58d54@google.com/ Cc: Breno Leitao leitao@debian.org Cc: Muchun Song muchun.song@linux.dev Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---
mm/hugetlb.c | 16 ++++++++++++++-- 1 file changed, 14 insertions(+), 2 deletions(-)
--- a/mm/hugetlb.c~mm-hugetlb-do-not-call-vma_add_reservation-upon-enomem +++ a/mm/hugetlb.c @@ -5768,8 +5768,20 @@ void __unmap_hugepage_range(struct mmu_g * do_exit() will not see it, and will keep the reservation * forever. */ - if (adjust_reservation && vma_needs_reservation(h, vma, address)) - vma_add_reservation(h, vma, address); + if (adjust_reservation) { + int rc = vma_needs_reservation(h, vma, address); + + if (rc < 0) + /* Pressumably allocate_file_region_entries failed + * to allocate a file_region struct. Clear + * hugetlb_restore_reserve so that global reserve + * count will not be incremented by free_huge_folio. + * Act as if we consumed the reservation. + */ + folio_clear_hugetlb_restore_reserve(page_folio(page)); + else if (rc) + vma_add_reservation(h, vma, address); + }
tlb_remove_page_size(tlb, page, huge_page_size(h)); /* _
Patches currently in -mm which might be from osalvador@suse.de are
mm-hugetlb-do-not-call-vma_add_reservation-upon-enomem.patch mm-hugetlb-drop-node_alloc_noretry-from-alloc_fresh_hugetlb_folio.patch