The quilt patch titled
Subject: mm: call wp_page_copy() under the VMA lock
has been removed from the -mm tree. Its filename was
mm-call-wp_page_copy-under-the-vma-lock.patch
This patch was dropped because it was merged into the mm-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
------------------------------------------------------
From: "Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx>
Subject: mm: call wp_page_copy() under the VMA lock
Date: Fri, 6 Oct 2023 20:53:14 +0100
It is usually safe to call wp_page_copy() under the VMA lock. The only
unsafe situation is when no anon_vma has been allocated for this VMA, and
we have to look at adjacent VMAs to determine if their anon_vma can be
shared. Since this happens only for the first COW of a page in this VMA,
the majority of calls to wp_page_copy() do not need to fall back to the
mmap_sem.
Add vmf_anon_prepare() as an alternative to anon_vma_prepare() which will
return RETRY if we currently hold the VMA lock and need to allocate an
anon_vma. This lets us drop the check in do_wp_page().
Link: https://lkml.kernel.org/r/20231006195318.4087158-3-willy@xxxxxxxxxxxxx
Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Reviewed-by: Suren Baghdasaryan <surenb@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/memory.c | 39 ++++++++++++++++++++++++++-------------
1 file changed, 26 insertions(+), 13 deletions(-)
--- a/mm/memory.c~mm-call-wp_page_copy-under-the-vma-lock
+++ a/mm/memory.c
@@ -3042,6 +3042,21 @@ static inline void wp_page_reuse(struct
count_vm_event(PGREUSE);
}
+static vm_fault_t vmf_anon_prepare(struct vm_fault *vmf)
+{
+ struct vm_area_struct *vma = vmf->vma;
+
+ if (likely(vma->anon_vma))
+ return 0;
+ if (vmf->flags & FAULT_FLAG_VMA_LOCK) {
+ vma_end_read(vma);
+ return VM_FAULT_RETRY;
+ }
+ if (__anon_vma_prepare(vma))
+ return VM_FAULT_OOM;
+ return 0;
+}
+
/*
* Handle the case of a page which we actually need to copy to a new page,
* either due to COW or unsharing.
@@ -3069,27 +3084,29 @@ static vm_fault_t wp_page_copy(struct vm
pte_t entry;
int page_copied = 0;
struct mmu_notifier_range range;
- int ret;
+ vm_fault_t ret;
delayacct_wpcopy_start();
if (vmf->page)
old_folio = page_folio(vmf->page);
- if (unlikely(anon_vma_prepare(vma)))
- goto oom;
+ ret = vmf_anon_prepare(vmf);
+ if (unlikely(ret))
+ goto out;
if (is_zero_pfn(pte_pfn(vmf->orig_pte))) {
new_folio = vma_alloc_zeroed_movable_folio(vma, vmf->address);
if (!new_folio)
goto oom;
} else {
+ int err;
new_folio = vma_alloc_folio(GFP_HIGHUSER_MOVABLE, 0, vma,
vmf->address, false);
if (!new_folio)
goto oom;
- ret = __wp_page_copy_user(&new_folio->page, vmf->page, vmf);
- if (ret) {
+ err = __wp_page_copy_user(&new_folio->page, vmf->page, vmf);
+ if (err) {
/*
* COW failed, if the fault was solved by other,
* it's fine. If not, userspace would re-fault on
@@ -3102,7 +3119,7 @@ static vm_fault_t wp_page_copy(struct vm
folio_put(old_folio);
delayacct_wpcopy_end();
- return ret == -EHWPOISON ? VM_FAULT_HWPOISON : 0;
+ return err == -EHWPOISON ? VM_FAULT_HWPOISON : 0;
}
kmsan_copy_page_meta(&new_folio->page, vmf->page);
}
@@ -3212,11 +3229,13 @@ static vm_fault_t wp_page_copy(struct vm
oom_free_new:
folio_put(new_folio);
oom:
+ ret = VM_FAULT_OOM;
+out:
if (old_folio)
folio_put(old_folio);
delayacct_wpcopy_end();
- return VM_FAULT_OOM;
+ return ret;
}
/**
@@ -3458,12 +3477,6 @@ reuse:
return 0;
}
copy:
- if ((vmf->flags & FAULT_FLAG_VMA_LOCK) && !vma->anon_vma) {
- pte_unmap_unlock(vmf->pte, vmf->ptl);
- vma_end_read(vmf->vma);
- return VM_FAULT_RETRY;
- }
-
/*
* Ok, we need to copy. Oh, well..
*/
_
Patches currently in -mm which might be from willy@xxxxxxxxxxxxx are
buffer-make-folio_create_empty_buffers-return-a-buffer_head.patch
mpage-convert-map_buffer_to_folio-to-folio_create_empty_buffers.patch
ext4-convert-to-folio_create_empty_buffers.patch
buffer-add-get_nth_bh.patch
gfs2-convert-inode-unstuffing-to-use-a-folio.patch
gfs2-convert-gfs2_getbuf-to-folios.patch
gfs2-convert-gfs2_getjdatabuf-to-use-a-folio.patch
gfs2-convert-gfs2_write_buf_to_page-to-use-a-folio.patch
nilfs2-convert-nilfs_mdt_freeze_buffer-to-use-a-folio.patch
nilfs2-convert-nilfs_grab_buffer-to-use-a-folio.patch
nilfs2-convert-nilfs_copy_page-to-nilfs_copy_folio.patch
nilfs2-convert-nilfs_mdt_forget_block-to-use-a-folio.patch
nilfs2-convert-nilfs_mdt_get_frozen_buffer-to-use-a-folio.patch
nilfs2-remove-nilfs_page_get_nth_block.patch
nilfs2-convert-nilfs_lookup_dirty_data_buffers-to-use-folio_create_empty_buffers.patch
ntfs-convert-ntfs_read_block-to-use-a-folio.patch
ntfs-convert-ntfs_writepage-to-use-a-folio.patch
ntfs-convert-ntfs_prepare_pages_for_non_resident_write-to-folios.patch
ntfs3-convert-ntfs_zero_range-to-use-a-folio.patch
ocfs2-convert-ocfs2_map_page_blocks-to-use-a-folio.patch
reiserfs-convert-writepage-to-use-a-folio.patch
ufs-add-ufs_get_locked_folio-and-ufs_put_locked_folio.patch
ufs-use-ufs_get_locked_folio-in-ufs_alloc_lastblock.patch
ufs-convert-ufs_change_blocknr-to-use-folios.patch
ufs-remove-ufs_get_locked_page.patch
buffer-remove-folio_create_empty_buffers.patch
