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rmap: drop support of non-linear mappings 

We don't create non-linear mappings anymore.  Let's drop code which
handles them in rmap.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Kirill A. Shutemov 2015-02-10 14:09:59 -08:00 committed by Linus Torvalds
parent 1da4b35b00
commit 27ba0644ea
11 changed files with 18 additions and 300 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
Documentation/cachetlb.txt
View File

@ -317,10 +317,10 @@ maps this page at its virtual address.
about doing this.
The idea is, first at flush_dcache_page() time, if
page->mapping->i_mmap is an empty tree and ->i_mmap_nonlinear
an empty list, just mark the architecture private page flag bit.
Later, in update_mmu_cache(), a check is made of this flag bit,
and if set the flush is done and the flag bit is cleared.
page->mapping->i_mmap is an empty tree, just mark the architecture
private page flag bit. Later, in update_mmu_cache(), a check is
made of this flag bit, and if set the flush is done and the flag
bit is cleared.
IMPORTANT NOTE: It is often important, if you defer the flush,
that the actual flush occurs on the same CPU

1
fs/inode.c
View File

@ -355,7 +355,6 @@ void address_space_init_once(struct address_space *mapping)
INIT_LIST_HEAD(&mapping->private_list);
spin_lock_init(&mapping->private_lock);
mapping->i_mmap = RB_ROOT;
INIT_LIST_HEAD(&mapping->i_mmap_nonlinear);
}
EXPORT_SYMBOL(address_space_init_once);

4
include/linux/fs.h
View File

@ -401,7 +401,6 @@ struct address_space {
spinlock_t tree_lock; /* and lock protecting it */
atomic_t i_mmap_writable;/* count VM_SHARED mappings */
struct rb_root i_mmap; /* tree of private and shared mappings */
struct list_head i_mmap_nonlinear;/*list VM_NONLINEAR mappings */
struct rw_semaphore i_mmap_rwsem; /* protect tree, count, list */
/* Protected by tree_lock together with the radix tree */
unsigned long nrpages; /* number of total pages */
@ -493,8 +492,7 @@ static inline void i_mmap_unlock_read(struct address_space *mapping)
*/
static inline int mapping_mapped(struct address_space *mapping)
{
return !RB_EMPTY_ROOT(&mapping->i_mmap) ||
!list_empty(&mapping->i_mmap_nonlinear);
return !RB_EMPTY_ROOT(&mapping->i_mmap);
}
/*

6
include/linux/mm.h
View File

@ -1796,12 +1796,6 @@ struct vm_area_struct *vma_interval_tree_iter_next(struct vm_area_struct *node,
for (vma = vma_interval_tree_iter_first(root, start, last); \
vma; vma = vma_interval_tree_iter_next(vma, start, last))
static inline void vma_nonlinear_insert(struct vm_area_struct *vma,
struct list_head *list)
{
list_add_tail(&vma->shared.nonlinear, list);
}
void anon_vma_interval_tree_insert(struct anon_vma_chain *node,
struct rb_root *root);
void anon_vma_interval_tree_remove(struct anon_vma_chain *node,

4
include/linux/mm_types.h
View File

@ -273,15 +273,13 @@ struct vm_area_struct {
/*
* For areas with an address space and backing store,
* linkage into the address_space->i_mmap interval tree, or
* linkage of vma in the address_space->i_mmap_nonlinear list.
* linkage into the address_space->i_mmap interval tree.
*/
union {
struct {
struct rb_node rb;
unsigned long rb_subtree_last;
} linear;
struct list_head nonlinear;
} shared;
/*

2
include/linux/rmap.h
View File

@ -246,7 +246,6 @@ int page_mapped_in_vma(struct page *page, struct vm_area_struct *vma);
* arg: passed to rmap_one() and invalid_vma()
* rmap_one: executed on each vma where page is mapped
* done: for checking traversing termination condition
* file_nonlinear: for handling file nonlinear mapping
* anon_lock: for getting anon_lock by optimized way rather than default
* invalid_vma: for skipping uninterested vma
*/
@ -255,7 +254,6 @@ struct rmap_walk_control {
int (*rmap_one)(struct page *page, struct vm_area_struct *vma,
unsigned long addr, void *arg);
int (*done)(struct page *page);
int (*file_nonlinear)(struct page *, struct address_space *, void *arg);
struct anon_vma *(*anon_lock)(struct page *page);
bool (*invalid_vma)(struct vm_area_struct *vma, void *arg);
};

8
kernel/fork.c
View File

@ -438,12 +438,8 @@ static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
atomic_inc(&mapping->i_mmap_writable);
flush_dcache_mmap_lock(mapping);
/* insert tmp into the share list, just after mpnt */
if (unlikely(tmp->vm_flags & VM_NONLINEAR))
vma_nonlinear_insert(tmp,
&mapping->i_mmap_nonlinear);
else
vma_interval_tree_insert_after(tmp, mpnt,
&mapping->i_mmap);
vma_interval_tree_insert_after(tmp, mpnt,
&mapping->i_mmap);
flush_dcache_mmap_unlock(mapping);
i_mmap_unlock_write(mapping);
}

32
mm/migrate.c
View File

@ -178,37 +178,6 @@ static int remove_migration_pte(struct page *new, struct vm_area_struct *vma,
return SWAP_AGAIN;
}
/*
* Congratulations to trinity for discovering this bug.
* mm/fremap.c's remap_file_pages() accepts any range within a single vma to
* convert that vma to VM_NONLINEAR; and generic_file_remap_pages() will then
* replace the specified range by file ptes throughout (maybe populated after).
* If page migration finds a page within that range, while it's still located
* by vma_interval_tree rather than lost to i_mmap_nonlinear list, no problem:
* zap_pte() clears the temporary migration entry before mmap_sem is dropped.
* But if the migrating page is in a part of the vma outside the range to be
* remapped, then it will not be cleared, and remove_migration_ptes() needs to
* deal with it. Fortunately, this part of the vma is of course still linear,
* so we just need to use linear location on the nonlinear list.
*/
static int remove_linear_migration_ptes_from_nonlinear(struct page *page,
struct address_space *mapping, void *arg)
{
struct vm_area_struct *vma;
/* hugetlbfs does not support remap_pages, so no huge pgoff worries */
pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
unsigned long addr;
list_for_each_entry(vma,
&mapping->i_mmap_nonlinear, shared.nonlinear) {
addr = vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT);
if (addr >= vma->vm_start && addr < vma->vm_end)
remove_migration_pte(page, vma, addr, arg);
}
return SWAP_AGAIN;
}
/*
* Get rid of all migration entries and replace them by
* references to the indicated page.
@ -218,7 +187,6 @@ static void remove_migration_ptes(struct page *old, struct page *new)
struct rmap_walk_control rwc = {
.rmap_one = remove_migration_pte,
.arg = old,
.file_nonlinear = remove_linear_migration_ptes_from_nonlinear,
};
rmap_walk(new, &rwc);

24
mm/mmap.c
View File

@ -243,10 +243,7 @@ static void __remove_shared_vm_struct(struct vm_area_struct *vma,
mapping_unmap_writable(mapping);
flush_dcache_mmap_lock(mapping);
if (unlikely(vma->vm_flags & VM_NONLINEAR))
list_del_init(&vma->shared.nonlinear);
else
vma_interval_tree_remove(vma, &mapping->i_mmap);
vma_interval_tree_remove(vma, &mapping->i_mmap);
flush_dcache_mmap_unlock(mapping);
}
@ -649,10 +646,7 @@ static void __vma_link_file(struct vm_area_struct *vma)
atomic_inc(&mapping->i_mmap_writable);
flush_dcache_mmap_lock(mapping);
if (unlikely(vma->vm_flags & VM_NONLINEAR))
vma_nonlinear_insert(vma, &mapping->i_mmap_nonlinear);
else
vma_interval_tree_insert(vma, &mapping->i_mmap);
vma_interval_tree_insert(vma, &mapping->i_mmap);
flush_dcache_mmap_unlock(mapping);
}
}
@ -789,14 +783,11 @@ again: remove_next = 1 + (end > next->vm_end);
if (file) {
mapping = file->f_mapping;
if (!(vma->vm_flags & VM_NONLINEAR)) {
root = &mapping->i_mmap;
uprobe_munmap(vma, vma->vm_start, vma->vm_end);
root = &mapping->i_mmap;
uprobe_munmap(vma, vma->vm_start, vma->vm_end);
if (adjust_next)
uprobe_munmap(next, next->vm_start,
next->vm_end);
}
if (adjust_next)
uprobe_munmap(next, next->vm_start, next->vm_end);
i_mmap_lock_write(mapping);
if (insert) {
@ -3177,8 +3168,7 @@ static void vm_lock_mapping(struct mm_struct *mm, struct address_space *mapping)
*
* mmap_sem in write mode is required in order to block all operations
* that could modify pagetables and free pages without need of
* altering the vma layout (for example populate_range() with
* nonlinear vmas). It's also needed in write mode to avoid new
* altering the vma layout. It's also needed in write mode to avoid new
* anon_vmas to be associated with existing vmas.
*
* A single task can't take more than one mm_take_all_locks() in a row

225
mm/rmap.c
View File

@ -590,9 +590,8 @@ unsigned long page_address_in_vma(struct page *page, struct vm_area_struct *vma)
if (!vma->anon_vma || !page__anon_vma ||
vma->anon_vma->root != page__anon_vma->root)
return -EFAULT;
} else if (page->mapping && !(vma->vm_flags & VM_NONLINEAR)) {
if (!vma->vm_file ||
vma->vm_file->f_mapping != page->mapping)
} else if (page->mapping) {
if (!vma->vm_file || vma->vm_file->f_mapping != page->mapping)
return -EFAULT;
} else
return -EFAULT;
@ -1274,7 +1273,6 @@ static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
if (pte_soft_dirty(pteval))
swp_pte = pte_swp_mksoft_dirty(swp_pte);
set_pte_at(mm, address, pte, swp_pte);
BUG_ON(pte_file(*pte));
} else if (IS_ENABLED(CONFIG_MIGRATION) &&
(flags & TTU_MIGRATION)) {
/* Establish migration entry for a file page */
@ -1316,211 +1314,6 @@ static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
return ret;
}
/*
* objrmap doesn't work for nonlinear VMAs because the assumption that
* offset-into-file correlates with offset-into-virtual-addresses does not hold.
* Consequently, given a particular page and its ->index, we cannot locate the
* ptes which are mapping that page without an exhaustive linear search.
*
* So what this code does is a mini "virtual scan" of each nonlinear VMA which
* maps the file to which the target page belongs. The ->vm_private_data field
* holds the current cursor into that scan. Successive searches will circulate
* around the vma's virtual address space.
*
* So as more replacement pressure is applied to the pages in a nonlinear VMA,
* more scanning pressure is placed against them as well. Eventually pages
* will become fully unmapped and are eligible for eviction.
*
* For very sparsely populated VMAs this is a little inefficient - chances are
* there there won't be many ptes located within the scan cluster. In this case
* maybe we could scan further - to the end of the pte page, perhaps.
*
* Mlocked pages: check VM_LOCKED under mmap_sem held for read, if we can
* acquire it without blocking. If vma locked, mlock the pages in the cluster,
* rather than unmapping them. If we encounter the "check_page" that vmscan is
* trying to unmap, return SWAP_MLOCK, else default SWAP_AGAIN.
*/
#define CLUSTER_SIZE min(32*PAGE_SIZE, PMD_SIZE)
#define CLUSTER_MASK (~(CLUSTER_SIZE - 1))
static int try_to_unmap_cluster(unsigned long cursor, unsigned int *mapcount,
struct vm_area_struct *vma, struct page *check_page)
{
struct mm_struct *mm = vma->vm_mm;
pmd_t *pmd;
pte_t *pte;
pte_t pteval;
spinlock_t *ptl;
struct page *page;
unsigned long address;
unsigned long mmun_start; /* For mmu_notifiers */
unsigned long mmun_end; /* For mmu_notifiers */
unsigned long end;
int ret = SWAP_AGAIN;
int locked_vma = 0;
address = (vma->vm_start + cursor) & CLUSTER_MASK;
end = address + CLUSTER_SIZE;
if (address < vma->vm_start)
address = vma->vm_start;
if (end > vma->vm_end)
end = vma->vm_end;
pmd = mm_find_pmd(mm, address);
if (!pmd)
return ret;
mmun_start = address;
mmun_end = end;
mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
/*
* If we can acquire the mmap_sem for read, and vma is VM_LOCKED,
* keep the sem while scanning the cluster for mlocking pages.
*/
if (down_read_trylock(&vma->vm_mm->mmap_sem)) {
locked_vma = (vma->vm_flags & VM_LOCKED);
if (!locked_vma)
up_read(&vma->vm_mm->mmap_sem); /* don't need it */
}
pte = pte_offset_map_lock(mm, pmd, address, &ptl);
/* Update high watermark before we lower rss */
update_hiwater_rss(mm);
for (; address < end; pte++, address += PAGE_SIZE) {
if (!pte_present(*pte))
continue;
page = vm_normal_page(vma, address, *pte);
BUG_ON(!page || PageAnon(page));
if (locked_vma) {
if (page == check_page) {
/* we know we have check_page locked */
mlock_vma_page(page);
ret = SWAP_MLOCK;
} else if (trylock_page(page)) {
/*
* If we can lock the page, perform mlock.
* Otherwise leave the page alone, it will be
* eventually encountered again later.
*/
mlock_vma_page(page);
unlock_page(page);
}
continue; /* don't unmap */
}
/*
* No need for _notify because we're within an
* mmu_notifier_invalidate_range_ {start|end} scope.
*/
if (ptep_clear_flush_young(vma, address, pte))
continue;
/* Nuke the page table entry. */
flush_cache_page(vma, address, pte_pfn(*pte));
pteval = ptep_clear_flush_notify(vma, address, pte);
/* If nonlinear, store the file page offset in the pte. */
if (page->index != linear_page_index(vma, address)) {
pte_t ptfile = pgoff_to_pte(page->index);
if (pte_soft_dirty(pteval))
ptfile = pte_file_mksoft_dirty(ptfile);
set_pte_at(mm, address, pte, ptfile);
}
/* Move the dirty bit to the physical page now the pte is gone. */
if (pte_dirty(pteval))
set_page_dirty(page);
page_remove_rmap(page);
page_cache_release(page);
dec_mm_counter(mm, MM_FILEPAGES);
(*mapcount)--;
}
pte_unmap_unlock(pte - 1, ptl);
mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
if (locked_vma)
up_read(&vma->vm_mm->mmap_sem);
return ret;
}
static int try_to_unmap_nonlinear(struct page *page,
struct address_space *mapping, void *arg)
{
struct vm_area_struct *vma;
int ret = SWAP_AGAIN;
unsigned long cursor;
unsigned long max_nl_cursor = 0;
unsigned long max_nl_size = 0;
unsigned int mapcount;
list_for_each_entry(vma,
&mapping->i_mmap_nonlinear, shared.nonlinear) {
cursor = (unsigned long) vma->vm_private_data;
if (cursor > max_nl_cursor)
max_nl_cursor = cursor;
cursor = vma->vm_end - vma->vm_start;
if (cursor > max_nl_size)
max_nl_size = cursor;
}
if (max_nl_size == 0) { /* all nonlinears locked or reserved ? */
return SWAP_FAIL;
}
/*
* We don't try to search for this page in the nonlinear vmas,
* and page_referenced wouldn't have found it anyway. Instead
* just walk the nonlinear vmas trying to age and unmap some.
* The mapcount of the page we came in with is irrelevant,
* but even so use it as a guide to how hard we should try?
*/
mapcount = page_mapcount(page);
if (!mapcount)
return ret;
cond_resched();
max_nl_size = (max_nl_size + CLUSTER_SIZE - 1) & CLUSTER_MASK;
if (max_nl_cursor == 0)
max_nl_cursor = CLUSTER_SIZE;
do {
list_for_each_entry(vma,
&mapping->i_mmap_nonlinear, shared.nonlinear) {
cursor = (unsigned long) vma->vm_private_data;
while (cursor < max_nl_cursor &&
cursor < vma->vm_end - vma->vm_start) {
if (try_to_unmap_cluster(cursor, &mapcount,
vma, page) == SWAP_MLOCK)
ret = SWAP_MLOCK;
cursor += CLUSTER_SIZE;
vma->vm_private_data = (void *) cursor;
if ((int)mapcount <= 0)
return ret;
}
vma->vm_private_data = (void *) max_nl_cursor;
}
cond_resched();
max_nl_cursor += CLUSTER_SIZE;
} while (max_nl_cursor <= max_nl_size);
/*
* Don't loop forever (perhaps all the remaining pages are
* in locked vmas). Reset cursor on all unreserved nonlinear
* vmas, now forgetting on which ones it had fallen behind.
*/
list_for_each_entry(vma, &mapping->i_mmap_nonlinear, shared.nonlinear)
vma->vm_private_data = NULL;
return ret;
}
bool is_vma_temporary_stack(struct vm_area_struct *vma)
{
int maybe_stack = vma->vm_flags & (VM_GROWSDOWN | VM_GROWSUP);
@ -1566,7 +1359,6 @@ int try_to_unmap(struct page *page, enum ttu_flags flags)
.rmap_one = try_to_unmap_one,
.arg = (void *)flags,
.done = page_not_mapped,
.file_nonlinear = try_to_unmap_nonlinear,
.anon_lock = page_lock_anon_vma_read,
};
@ -1612,12 +1404,6 @@ int try_to_munlock(struct page *page)
.rmap_one = try_to_unmap_one,
.arg = (void *)TTU_MUNLOCK,
.done = page_not_mapped,
/*
* We don't bother to try to find the munlocked page in
* nonlinears. It's costly. Instead, later, page reclaim logic
* may call try_to_unmap() and recover PG_mlocked lazily.
*/
.file_nonlinear = NULL,
.anon_lock = page_lock_anon_vma_read,
};
@ -1748,13 +1534,6 @@ static int rmap_walk_file(struct page *page, struct rmap_walk_control *rwc)
goto done;
}
if (!rwc->file_nonlinear)
goto done;
if (list_empty(&mapping->i_mmap_nonlinear))
goto done;
ret = rwc->file_nonlinear(page, mapping, rwc->arg);
done:
i_mmap_unlock_read(mapping);
return ret;

4
mm/swap.c
View File

@ -1140,10 +1140,8 @@ void __init swap_setup(void)
if (bdi_init(swapper_spaces[0].backing_dev_info))
panic("Failed to init swap bdi");
for (i = 0; i < MAX_SWAPFILES; i++) {
for (i = 0; i < MAX_SWAPFILES; i++)
spin_lock_init(&swapper_spaces[i].tree_lock);
INIT_LIST_HEAD(&swapper_spaces[i].i_mmap_nonlinear);
}
#endif
/* Use a smaller cluster for small-memory machines */