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mm/rmap: split try_to_munlock from try_to_unmap

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The behaviour of try_to_unmap_one() is difficult to follow because it
performs different operations based on a fairly large set of flags used in
different combinations.

TTU_MUNLOCK is one such flag.  However it is exclusively used by
try_to_munlock() which specifies no other flags.  Therefore rather than
overload try_to_unmap_one() with unrelated behaviour split this out into
it's own function and remove the flag.

Link: https://lkml.kernel.org/r/20210616105937.23201-4-apopple@nvidia.com
Signed-off-by: Alistair Popple <apopple@nvidia.com>
Reviewed-by: Ralph Campbell <rcampbell@nvidia.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: Ben Skeggs <bskeggs@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Cc: Peter Xu <peterx@redhat.com>
Cc: Shakeel Butt <shakeelb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Alistair Popple
2021-06-30 18:54:12 -07:00
committed by Linus Torvalds
parent 4dd845b5a3
commit cd62734ca6
4 changed files with 70 additions and 46 deletions
Download Patch File Download Diff File Expand all files Collapse all files

68
mm/rmap.c
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@@ -1411,10 +1411,6 @@ static bool try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
if (flags & TTU_SYNC)
pvmw.flags = PVMW_SYNC;
/* munlock has nothing to gain from examining un-locked vmas */
if ((flags & TTU_MUNLOCK) && !(vma->vm_flags & VM_LOCKED))
return true;
if (IS_ENABLED(CONFIG_MIGRATION) && (flags & TTU_MIGRATION) &&
is_zone_device_page(page) && !is_device_private_page(page))
return true;
@@ -1476,8 +1472,6 @@ static bool try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
page_vma_mapped_walk_done(&pvmw);
break;
}
if (flags & TTU_MUNLOCK)
continue;
}
/* Unexpected PMD-mapped THP? */
@@ -1790,20 +1784,58 @@ void try_to_unmap(struct page *page, enum ttu_flags flags)
rmap_walk(page, &rwc);
}
/**
* try_to_munlock - try to munlock a page
* @page: the page to be munlocked
*
* Called from munlock code. Checks all of the VMAs mapping the page
* to make sure nobody else has this page mlocked. The page will be
* returned with PG_mlocked cleared if no other vmas have it mlocked.
/*
* Walks the vma's mapping a page and mlocks the page if any locked vma's are
* found. Once one is found the page is locked and the scan can be terminated.
*/
static bool page_mlock_one(struct page *page, struct vm_area_struct *vma,
unsigned long address, void *unused)
{
struct page_vma_mapped_walk pvmw = {
.page = page,
.vma = vma,
.address = address,
};
void try_to_munlock(struct page *page)
/* An un-locked vma doesn't have any pages to lock, continue the scan */
if (!(vma->vm_flags & VM_LOCKED))
return true;
while (page_vma_mapped_walk(&pvmw)) {
/*
* Need to recheck under the ptl to serialise with
* __munlock_pagevec_fill() after VM_LOCKED is cleared in
* munlock_vma_pages_range().
*/
if (vma->vm_flags & VM_LOCKED) {
/* PTE-mapped THP are never mlocked */
if (!PageTransCompound(page))
mlock_vma_page(page);
page_vma_mapped_walk_done(&pvmw);
}
/*
* no need to continue scanning other vma's if the page has
* been locked.
*/
return false;
}
return true;
}
/**
* page_mlock - try to mlock a page
* @page: the page to be mlocked
*
* Called from munlock code. Checks all of the VMAs mapping the page and mlocks
* the page if any are found. The page will be returned with PG_mlocked cleared
* if it is not mapped by any locked vmas.
*/
void page_mlock(struct page *page)
{
struct rmap_walk_control rwc = {
.rmap_one = try_to_unmap_one,
.arg = (void *)TTU_MUNLOCK,
.rmap_one = page_mlock_one,
.done = page_not_mapped,
.anon_lock = page_lock_anon_vma_read,
@@ -1855,7 +1887,7 @@ static struct anon_vma *rmap_walk_anon_lock(struct page *page,
* Find all the mappings of a page using the mapping pointer and the vma chains
* contained in the anon_vma struct it points to.
*
* When called from try_to_munlock(), the mmap_lock of the mm containing the vma
* When called from page_mlock(), the mmap_lock of the mm containing the vma
* where the page was found will be held for write. So, we won't recheck
* vm_flags for that VMA. That should be OK, because that vma shouldn't be
* LOCKED.
@@ -1908,7 +1940,7 @@ static void rmap_walk_anon(struct page *page, struct rmap_walk_control *rwc,
* Find all the mappings of a page using the mapping pointer and the vma chains
* contained in the address_space struct it points to.
*
* When called from try_to_munlock(), the mmap_lock of the mm containing the vma
* When called from page_mlock(), the mmap_lock of the mm containing the vma
* where the page was found will be held for write. So, we won't recheck
* vm_flags for that VMA. That should be OK, because that vma shouldn't be
* LOCKED.