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Subject[PATCH -mm 17/25] Mlocked Pages are non-reclaimable
Originally
From: Nick Piggin <npiggin@suse.de>

Against: 2.6.26-rc2-mm1

This patch:

1) defines the [CONFIG_]NORECLAIM_MLOCK sub-option and the
stub version of the mlock/noreclaim APIs when it's
not configured. Depends on [CONFIG_]NORECLAIM_LRU.

2) add yet another page flag--PG_mlocked--to indicate that
the page is locked for efficient testing in vmscan and,
optionally, fault path. This allows early culling of
nonreclaimable pages, preventing them from getting to
page_referenced()/try_to_unmap(). Also allows separate
accounting of mlock'd pages, as Nick's original patch
did.

Note: Nick's original mlock patch used a PG_mlocked
flag. I had removed this in favor of the PG_noreclaim
flag + an mlock_count [new page struct member]. I
restored the PG_mlocked flag to eliminate the new
count field.

3) add the mlock/noreclaim infrastructure to mm/mlock.c,
with internal APIs in mm/internal.h. This is a rework
of Nick's original patch to these files, taking into
account that mlocked pages are now kept on noreclaim
LRU list.

4) update vmscan.c:page_reclaimable() to check PageMlocked()
and, if vma passed in, the vm_flags. Note that the vma
will only be passed in for new pages in the fault path;
and then only if the "cull nonreclaimable pages in fault
path" patch is included.

5) add try_to_unlock() to rmap.c to walk a page's rmap and
ClearPageMlocked() if no other vmas have it mlocked.
Reuses as much of try_to_unmap() as possible. This
effectively replaces the use of one of the lru list links
as an mlock count. If this mechanism let's pages in mlocked
vmas leak through w/o PG_mlocked set [I don't know that it
does], we should catch them later in try_to_unmap(). One
hopes this will be rare, as it will be relatively expensive.

6) Kosaki: added munlock page table walk to avoid using
get_user_pages() for unlock. get_user_pages() is unreliable
for some vma protections.
Lee: modified to wait for in-flight migration to complete
to close munlock/migration race that could strand pages.

Original mm/internal.h, mm/rmap.c and mm/mlock.c changes:
Signed-off-by: Nick Piggin <npiggin@suse.de>

Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Lee Schermerhorn <lee.schermerhorn@hp.com>

---
V8:
+ more refinement of rmap interaction, including attempt to
handle mlocked pages in non-linear mappings.
+ cleanup of lockdep reported errors.
+ enhancement of munlock page table walker to detect and
handle pages under migration [migration ptes].

V6:
+ Kosaki-san and Rik van Riel: added check for "page mapped
in vma" to try_to_unlock() processing in try_to_unmap_anon().
+ Kosaki-san added munlock page table walker to avoid use of
get_user_pages() for munlock. get_user_pages() proved to be
unreliable for some types of vmas.
+ added filtering of "special" vmas. Some [_IO||_PFN] we skip
altogether. Others, we just "make_pages_present" to simulate
old behavior--i.e., populate page tables. Clear/don't set
VM_LOCKED in non-mlockable vmas so that we don't try to unlock
at exit/unmap time.
+ rework PG_mlock page flag definitions for new page flags
macros.
+ Clear PageMlocked when COWing a page into a VM_LOCKED vma
so we don't leave an mlocked page in another non-mlocked
vma. If the other vma[s] had the page mlocked, we'll re-mlock
it if/when we try to reclaim it. This is less expensive than
walking the rmap in the COW/fault path.
+ in vmscan:shrink_page_list(), avoid adding anon page to
the swap cache if it's in a VM_LOCKED vma, even tho'
PG_mlocked might not be set. Call try_to_unlock() to
determine this. As a result, we'll never try to unmap
an mlocked anon page.
+ in support of the above change, updated try_to_unlock()
to use same logic as try_to_unmap() when it encounters a
VM_LOCKED vma--call mlock_vma_page() directly. Added
stub try_to_unlock() for vmscan when NORECLAIM_MLOCK
not configured.
V4 -> V5:
+ fixed problem with placement of #ifdef CONFIG_NORECLAIM_MLOCK
in prep_new_page() [Thanks, minchan Kim!].

V3 -> V4:
+ Added #ifdef CONFIG_NORECLAIM_MLOCK, #endif around use of
PG_mlocked in free_page_check(), et al. Not defined for
32-bit builds.

V2 -> V3:
+ rebase to 23-mm1 atop RvR's split lru series
+ fix page flags macros for *PageMlocked() when not configured.
+ ensure lru_add_drain_all() runs on all cpus when NORECLAIM_MLOCK
configured. Was just for NUMA.

V1 -> V2:
+ moved this patch [and related patches] up to right after
ramdisk/ramfs and SHM_LOCKed patches.
+ add [back] missing put_page() in putback_lru_page().
This solved page leakage as seen by stats in previous
version.
+ fix up munlock_vma_page() to isolate page from lru
before calling try_to_unlock(). Think I detected a
race here.
+ use TestClearPageMlock() on old page in migrate.c's
migrate_page_copy() to clean up old page.
+ live dangerously: remove TestSetPageLocked() in
is_mlocked_vma()--should only be called on new pages in
the fault path--iff we chose to cull there [later patch].
+ Add PG_mlocked to free_pages_check() etc to detect mlock
state mismanagement.
NOTE: temporarily [???] commented out--tripping over it
under load. Why?

Rework of Nick Piggins's "mm: move mlocked pages off the LRU" patch
-- part 1 of 2.

include/linux/mm.h | 5
include/linux/page-flags.h | 16 +
include/linux/rmap.h | 14 +
mm/Kconfig | 14 +
mm/internal.h | 70 ++++++++
mm/memory.c | 19 ++
mm/migrate.c | 2
mm/mlock.c | 386 ++++++++++++++++++++++++++++++++++++++++++---
mm/mmap.c | 1
mm/page_alloc.c | 15 +
mm/rmap.c | 252 +++++++++++++++++++++++++----
mm/swap.c | 2
mm/vmscan.c | 40 +++-
13 files changed, 767 insertions(+), 69 deletions(-)
Index: linux-2.6.26-rc2-mm1/mm/Kconfig
===================================================================
--- linux-2.6.26-rc2-mm1.orig/mm/Kconfig 2008-06-06 16:05:15.000000000 -0400
+++ linux-2.6.26-rc2-mm1/mm/Kconfig 2008-06-06 16:06:28.000000000 -0400
@@ -215,3 +215,17 @@ config NORECLAIM_LRU
may be non-reclaimable because: they are locked into memory, they
are anonymous pages for which no swap space exists, or they are anon
pages that are expensive to unmap [long anon_vma "related vma" list.]
+
+config NORECLAIM_MLOCK
+ bool "Exclude mlock'ed pages from reclaim"
+ depends on NORECLAIM_LRU
+ help
+ Treats mlock'ed pages as no-reclaimable. Removing these pages from
+ the LRU [in]active lists avoids the overhead of attempting to reclaim
+ them. Pages marked non-reclaimable for this reason will become
+ reclaimable again when the last mlock is removed.
+ when no swap space exists. Removing these pages from the LRU lists
+ avoids the overhead of attempting to reclaim them. Pages marked
+ non-reclaimable for this reason will become reclaimable again when/if
+ sufficient swap space is added to the system.
+
Index: linux-2.6.26-rc2-mm1/mm/internal.h
===================================================================
--- linux-2.6.26-rc2-mm1.orig/mm/internal.h 2008-06-06 16:05:15.000000000 -0400
+++ linux-2.6.26-rc2-mm1/mm/internal.h 2008-06-06 16:06:28.000000000 -0400
@@ -56,6 +56,17 @@ static inline unsigned long page_order(s
return page_private(page);
}

+/*
+ * mlock all pages in this vma range. For mmap()/mremap()/...
+ */
+extern int mlock_vma_pages_range(struct vm_area_struct *vma,
+ unsigned long start, unsigned long end);
+
+/*
+ * munlock all pages in vma. For munmap() and exit().
+ */
+extern void munlock_vma_pages_all(struct vm_area_struct *vma);
+
#ifdef CONFIG_NORECLAIM_LRU
/*
* noreclaim_migrate_page() called only from migrate_page_copy() to
@@ -74,6 +85,65 @@ static inline void noreclaim_migrate_pag
}
#endif

+#ifdef CONFIG_NORECLAIM_MLOCK
+/*
+ * Called only in fault path via page_reclaimable() for a new page
+ * to determine if it's being mapped into a LOCKED vma.
+ * If so, mark page as mlocked.
+ */
+static inline int is_mlocked_vma(struct vm_area_struct *vma, struct page *page)
+{
+ VM_BUG_ON(PageLRU(page));
+
+ if (likely((vma->vm_flags & (VM_LOCKED | VM_SPECIAL)) != VM_LOCKED))
+ return 0;
+
+ SetPageMlocked(page);
+ return 1;
+}
+
+/*
+ * must be called with vma's mmap_sem held for read, and page locked.
+ */
+extern void mlock_vma_page(struct page *page);
+
+/*
+ * Clear the page's PageMlocked(). This can be useful in a situation where
+ * we want to unconditionally remove a page from the pagecache -- e.g.,
+ * on truncation or freeing.
+ *
+ * It is legal to call this function for any page, mlocked or not.
+ * If called for a page that is still mapped by mlocked vmas, all we do
+ * is revert to lazy LRU behaviour -- semantics are not broken.
+ */
+extern void __clear_page_mlock(struct page *page);
+static inline void clear_page_mlock(struct page *page)
+{
+ if (unlikely(TestClearPageMlocked(page)))
+ __clear_page_mlock(page);
+}
+
+/*
+ * mlock_migrate_page - called only from migrate_page_copy() to
+ * migrate the Mlocked page flag
+ */
+static inline void mlock_migrate_page(struct page *newpage, struct page *page)
+{
+ if (TestClearPageMlocked(page))
+ SetPageMlocked(newpage);
+}
+
+
+#else /* CONFIG_NORECLAIM_MLOCK */
+static inline int is_mlocked_vma(struct vm_area_struct *v, struct page *p)
+{
+ return 0;
+}
+static inline void clear_page_mlock(struct page *page) { }
+static inline void mlock_vma_page(struct page *page) { }
+static inline void mlock_migrate_page(struct page *new, struct page *old) { }
+
+#endif /* CONFIG_NORECLAIM_MLOCK */

/*
* FLATMEM and DISCONTIGMEM configurations use alloc_bootmem_node,
Index: linux-2.6.26-rc2-mm1/mm/mlock.c
===================================================================
--- linux-2.6.26-rc2-mm1.orig/mm/mlock.c 2008-05-15 11:20:15.000000000 -0400
+++ linux-2.6.26-rc2-mm1/mm/mlock.c 2008-06-06 16:06:28.000000000 -0400
@@ -8,10 +8,18 @@
#include <linux/capability.h>
#include <linux/mman.h>
#include <linux/mm.h>
+#include <linux/swap.h>
+#include <linux/swapops.h>
+#include <linux/pagemap.h>
#include <linux/mempolicy.h>
#include <linux/syscalls.h>
#include <linux/sched.h>
#include <linux/module.h>
+#include <linux/rmap.h>
+#include <linux/mmzone.h>
+#include <linux/hugetlb.h>
+
+#include "internal.h"

int can_do_mlock(void)
{
@@ -23,17 +31,354 @@ int can_do_mlock(void)
}
EXPORT_SYMBOL(can_do_mlock);

+#ifdef CONFIG_NORECLAIM_MLOCK
+/*
+ * Mlocked pages are marked with PageMlocked() flag for efficient testing
+ * in vmscan and, possibly, the fault path; and to support semi-accurate
+ * statistics.
+ *
+ * An mlocked page [PageMlocked(page)] is non-reclaimable. As such, it will
+ * be placed on the LRU "noreclaim" list, rather than the [in]active lists.
+ * The noreclaim list is an LRU sibling list to the [in]active lists.
+ * PageNoreclaim is set to indicate the non-reclaimable state.
+ *
+ * When lazy mlocking via vmscan, it is important to ensure that the
+ * vma's VM_LOCKED status is not concurrently being modified, otherwise we
+ * may have mlocked a page that is being munlocked. So lazy mlock must take
+ * the mmap_sem for read, and verify that the vma really is locked
+ * (see mm/rmap.c).
+ */
+
+/*
+ * LRU accounting for clear_page_mlock()
+ */
+void __clear_page_mlock(struct page *page)
+{
+ VM_BUG_ON(!PageLocked(page)); /* for LRU islolate/putback */
+
+ if (!isolate_lru_page(page)) {
+ putback_lru_page(page);
+ } else {
+ /*
+ * Try hard not to leak this page ...
+ */
+ lru_add_drain_all();
+ if (!isolate_lru_page(page))
+ putback_lru_page(page);
+ }
+}
+
+/*
+ * Mark page as mlocked if not already.
+ * If page on LRU, isolate and putback to move to noreclaim list.
+ */
+void mlock_vma_page(struct page *page)
+{
+ BUG_ON(!PageLocked(page));
+
+ if (!TestSetPageMlocked(page) && !isolate_lru_page(page))
+ putback_lru_page(page);
+}
+
+/*
+ * called from munlock()/munmap() path with page supposedly on the LRU.
+ *
+ * Note: unlike mlock_vma_page(), we can't just clear the PageMlocked
+ * [in try_to_unlock()] and then attempt to isolate the page. We must
+ * isolate the page() to keep others from messing with its noreclaim
+ * and mlocked state while trying to unlock. However, we pre-clear the
+ * mlocked state anyway as we might lose the isolation race and we might
+ * not get another chance to clear PageMlocked. If we successfully
+ * isolate the page and try_to_unlock() detects other VM_LOCKED vmas
+ * mapping the page, it will restore the PageMlocked state, unless the page
+ * is mapped in a non-linear vma. So, we go ahead and SetPageMlocked(),
+ * perhaps redundantly.
+ * If we lose the isolation race, and the page is mapped by other VM_LOCKED
+ * vmas, we'll detect this in vmscan--via try_to_unlock() or try_to_unmap()
+ * either of which will restore the PageMlocked state by calling
+ * mlock_vma_page() above, if it can grab the vma's mmap sem.
+ */
+static void munlock_vma_page(struct page *page)
+{
+ BUG_ON(!PageLocked(page));
+
+ if (TestClearPageMlocked(page) && !isolate_lru_page(page)) {
+ try_to_unlock(page);
+ putback_lru_page(page);
+ }
+}
+
+/*
+ * mlock a range of pages in the vma.
+ *
+ * This takes care of making the pages present too.
+ *
+ * vma->vm_mm->mmap_sem must be held for write.
+ */
+static int __mlock_vma_pages_range(struct vm_area_struct *vma,
+ unsigned long start, unsigned long end)
+{
+ struct mm_struct *mm = vma->vm_mm;
+ unsigned long addr = start;
+ struct page *pages[16]; /* 16 gives a reasonable batch */
+ int write = !!(vma->vm_flags & VM_WRITE);
+ int nr_pages = (end - start) / PAGE_SIZE;
+ int ret;
+
+ VM_BUG_ON(start & ~PAGE_MASK || end & ~PAGE_MASK);
+ VM_BUG_ON(start < vma->vm_start || end > vma->vm_end);
+ VM_BUG_ON(!rwsem_is_locked(&vma->vm_mm->mmap_sem));
+
+ lru_add_drain_all(); /* push cached pages to LRU */
+
+ while (nr_pages > 0) {
+ int i;
+
+ cond_resched();
+
+ /*
+ * get_user_pages makes pages present if we are
+ * setting mlock.
+ */
+ ret = get_user_pages(current, mm, addr,
+ min_t(int, nr_pages, ARRAY_SIZE(pages)),
+ write, 0, pages, NULL);
+ /*
+ * This can happen for, e.g., VM_NONLINEAR regions before
+ * a page has been allocated and mapped at a given offset,
+ * or for addresses that map beyond end of a file.
+ * We'll mlock the the pages if/when they get faulted in.
+ */
+ if (ret < 0)
+ break;
+ if (ret == 0) {
+ /*
+ * We know the vma is there, so the only time
+ * we cannot get a single page should be an
+ * error (ret < 0) case.
+ */
+ WARN_ON(1);
+ break;
+ }
+
+ lru_add_drain(); /* push cached pages to LRU */
+
+ for (i = 0; i < ret; i++) {
+ struct page *page = pages[i];
+
+ /*
+ * page might be truncated or migrated out from under
+ * us. Check after acquiring page lock.
+ */
+ lock_page(page);
+ if (page->mapping)
+ mlock_vma_page(page);
+ unlock_page(page);
+ put_page(page); /* ref from get_user_pages() */
+
+ /*
+ * here we assume that get_user_pages() has given us
+ * a list of virtually contiguous pages.
+ */
+ addr += PAGE_SIZE; /* for next get_user_pages() */
+ nr_pages--;
+ }
+ }
+
+ lru_add_drain_all(); /* to update stats */
+
+ return 0; /* count entire vma as locked_vm */
+}
+
+/*
+ * private structure for munlock page table walk
+ */
+struct munlock_page_walk {
+ struct vm_area_struct *vma;
+ pmd_t *pmd; /* for migration_entry_wait() */
+};
+
+/*
+ * munlock normal pages for present ptes
+ */
+static int __munlock_pte_handler(pte_t *ptep, unsigned long addr,
+ unsigned long end, void *private)
+{
+ struct munlock_page_walk *mpw = private;
+ swp_entry_t entry;
+ struct page *page;
+ pte_t pte;
+
+retry:
+ pte = *ptep;
+ /*
+ * If it's a swap pte, we might be racing with page migration.
+ */
+ if (unlikely(!pte_present(pte))) {
+ if (!is_swap_pte(pte))
+ goto out;
+ entry = pte_to_swp_entry(pte);
+ if (is_migration_entry(entry)) {
+ migration_entry_wait(mpw->vma->vm_mm, mpw->pmd, addr);
+ goto retry;
+ }
+ goto out;
+ }
+
+ page = vm_normal_page(mpw->vma, addr, pte);
+ if (!page)
+ goto out;
+
+ lock_page(page);
+ if (!page->mapping) {
+ unlock_page(page);
+ goto retry;
+ }
+ munlock_vma_page(page);
+ unlock_page(page);
+
+out:
+ return 0;
+}
+
+/*
+ * Save pmd for pte handler for waiting on migration entries
+ */
+static int __munlock_pmd_handler(pmd_t *pmd, unsigned long addr,
+ unsigned long end, void *private)
+{
+ struct munlock_page_walk *mpw = private;
+
+ mpw->pmd = pmd;
+ return 0;
+}
+
+static struct mm_walk munlock_page_walk = {
+ .pmd_entry = __munlock_pmd_handler,
+ .pte_entry = __munlock_pte_handler,
+};
+
+/*
+ * munlock a range of pages in the vma using standard page table walk.
+ *
+ * vma->vm_mm->mmap_sem must be held for write.
+ */
+static void __munlock_vma_pages_range(struct vm_area_struct *vma,
+ unsigned long start, unsigned long end)
+{
+ struct mm_struct *mm = vma->vm_mm;
+ struct munlock_page_walk mpw;
+
+ VM_BUG_ON(start & ~PAGE_MASK || end & ~PAGE_MASK);
+ VM_BUG_ON(!rwsem_is_locked(&vma->vm_mm->mmap_sem));
+ VM_BUG_ON(start < vma->vm_start);
+ VM_BUG_ON(end > vma->vm_end);
+
+ lru_add_drain_all(); /* push cached pages to LRU */
+ mpw.vma = vma;
+ (void)walk_page_range(mm, start, end, &munlock_page_walk, &mpw);
+ lru_add_drain_all(); /* to update stats */
+
+}
+
+#else /* CONFIG_NORECLAIM_MLOCK */
+
+/*
+ * Just make pages present if VM_LOCKED. No-op if unlocking.
+ */
+static int __mlock_vma_pages_range(struct vm_area_struct *vma,
+ unsigned long start, unsigned long end)
+{
+ if (vma->vm_flags & VM_LOCKED)
+ make_pages_present(start, end);
+ return 0;
+}
+
+/*
+ * munlock a range of pages in the vma -- no-op.
+ */
+static void __munlock_vma_pages_range(struct vm_area_struct *vma,
+ unsigned long start, unsigned long end)
+{
+}
+#endif /* CONFIG_NORECLAIM_MLOCK */
+
+/*
+ * mlock all pages in this vma range. For mmap()/mremap()/...
+ */
+int mlock_vma_pages_range(struct vm_area_struct *vma,
+ unsigned long start, unsigned long end)
+{
+ int nr_pages = (end - start) / PAGE_SIZE;
+ BUG_ON(!(vma->vm_flags & VM_LOCKED));
+
+ /*
+ * filter unlockable vmas
+ */
+ if (vma->vm_flags & (VM_IO | VM_PFNMAP))
+ goto no_mlock;
+
+ if ((vma->vm_flags & (VM_DONTEXPAND | VM_RESERVED)) ||
+ is_vm_hugetlb_page(vma) ||
+ vma == get_gate_vma(current))
+ goto make_present;
+
+ return __mlock_vma_pages_range(vma, start, end);
+
+make_present:
+ /*
+ * User mapped kernel pages or huge pages:
+ * make these pages present to populate the ptes, but
+ * fall thru' to reset VM_LOCKED--no need to unlock, and
+ * return nr_pages so these don't get counted against task's
+ * locked limit. huge pages are already counted against
+ * locked vm limit.
+ */
+ make_pages_present(start, end);
+
+no_mlock:
+ vma->vm_flags &= ~VM_LOCKED; /* and don't come back! */
+ return nr_pages; /* pages NOT mlocked */
+}
+
+
+/*
+ * munlock all pages in vma. For munmap() and exit().
+ */
+void munlock_vma_pages_all(struct vm_area_struct *vma)
+{
+ vma->vm_flags &= ~VM_LOCKED;
+ __munlock_vma_pages_range(vma, vma->vm_start, vma->vm_end);
+}
+
+/*
+ * mlock_fixup - handle mlock[all]/munlock[all] requests.
+ *
+ * Filters out "special" vmas -- VM_LOCKED never gets set for these, and
+ * munlock is a no-op. However, for some special vmas, we go ahead and
+ * populate the ptes via make_pages_present().
+ *
+ * For vmas that pass the filters, merge/split as appropriate.
+ */
static int mlock_fixup(struct vm_area_struct *vma, struct vm_area_struct **prev,
unsigned long start, unsigned long end, unsigned int newflags)
{
- struct mm_struct * mm = vma->vm_mm;
+ struct mm_struct *mm = vma->vm_mm;
pgoff_t pgoff;
- int pages;
+ int nr_pages;
int ret = 0;
+ int lock = newflags & VM_LOCKED;

- if (newflags == vma->vm_flags) {
- *prev = vma;
- goto out;
+ if (newflags == vma->vm_flags ||
+ (vma->vm_flags & (VM_IO | VM_PFNMAP)))
+ goto out; /* don't set VM_LOCKED, don't count */
+
+ if ((vma->vm_flags & (VM_DONTEXPAND | VM_RESERVED)) ||
+ is_vm_hugetlb_page(vma) ||
+ vma == get_gate_vma(current)) {
+ if (lock)
+ make_pages_present(start, end);
+ goto out; /* don't set VM_LOCKED, don't count */
}

pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT);
@@ -44,8 +389,6 @@ static int mlock_fixup(struct vm_area_st
goto success;
}

- *prev = vma;
-
if (start != vma->vm_start) {
ret = split_vma(mm, vma, start, 1);
if (ret)
@@ -60,24 +403,31 @@ static int mlock_fixup(struct vm_area_st

success:
/*
+ * Keep track of amount of locked VM.
+ */
+ nr_pages = (end - start) >> PAGE_SHIFT;
+ if (!lock)
+ nr_pages = -nr_pages;
+ mm->locked_vm += nr_pages;
+
+ /*
* vm_flags is protected by the mmap_sem held in write mode.
* It's okay if try_to_unmap_one unmaps a page just after we
- * set VM_LOCKED, make_pages_present below will bring it back.
+ * set VM_LOCKED, __mlock_vma_pages_range will bring it back.
*/
vma->vm_flags = newflags;

- /*
- * Keep track of amount of locked VM.
- */
- pages = (end - start) >> PAGE_SHIFT;
- if (newflags & VM_LOCKED) {
- pages = -pages;
- if (!(newflags & VM_IO))
- ret = make_pages_present(start, end);
- }
+ if (lock) {
+ ret = __mlock_vma_pages_range(vma, start, end);
+ if (ret > 0) {
+ mm->locked_vm -= ret;
+ ret = 0;
+ }
+ } else
+ __munlock_vma_pages_range(vma, start, end);

- mm->locked_vm -= pages;
out:
+ *prev = vma;
if (ret == -ENOMEM)
ret = -EAGAIN;
return ret;
Index: linux-2.6.26-rc2-mm1/mm/vmscan.c
===================================================================
--- linux-2.6.26-rc2-mm1.orig/mm/vmscan.c 2008-06-06 16:06:24.000000000 -0400
+++ linux-2.6.26-rc2-mm1/mm/vmscan.c 2008-06-06 16:06:28.000000000 -0400
@@ -537,11 +537,8 @@ static unsigned long shrink_page_list(st

sc->nr_scanned++;

- if (unlikely(!page_reclaimable(page, NULL))) {
- if (putback_lru_page(page))
- unlock_page(page);
- continue;
- }
+ if (unlikely(!page_reclaimable(page, NULL)))
+ goto cull_mlocked;

if (!sc->may_swap && page_mapped(page))
goto keep_locked;
@@ -578,9 +575,19 @@ static unsigned long shrink_page_list(st
* Anonymous process memory has backing store?
* Try to allocate it some swap space here.
*/
- if (PageAnon(page) && !PageSwapCache(page))
+ if (PageAnon(page) && !PageSwapCache(page)) {
+ switch (try_to_unlock(page)) {
+ case SWAP_FAIL: /* shouldn't happen */
+ case SWAP_AGAIN:
+ goto keep_locked;
+ case SWAP_MLOCK:
+ goto cull_mlocked;
+ case SWAP_SUCCESS:
+ ; /* fall thru'; add to swap cache */
+ }
if (!add_to_swap(page, GFP_ATOMIC))
goto activate_locked;
+ }
#endif /* CONFIG_SWAP */

mapping = page_mapping(page);
@@ -595,6 +602,8 @@ static unsigned long shrink_page_list(st
goto activate_locked;
case SWAP_AGAIN:
goto keep_locked;
+ case SWAP_MLOCK:
+ goto cull_mlocked;
case SWAP_SUCCESS:
; /* try to free the page below */
}
@@ -667,6 +676,11 @@ free_it:
__pagevec_release_nonlru(&freed_pvec);
continue;

+cull_mlocked:
+ if (putback_lru_page(page))
+ unlock_page(page);
+ continue;
+
activate_locked:
/* Not a candidate for swapping, so reclaim swap space. */
if (PageSwapCache(page) && vm_swap_full())
@@ -678,7 +692,7 @@ keep_locked:
unlock_page(page);
keep:
list_add(&page->lru, &ret_pages);
- VM_BUG_ON(PageLRU(page));
+ VM_BUG_ON(PageLRU(page) || PageNoreclaim(page));
}
list_splice(&ret_pages, page_list);
if (pagevec_count(&freed_pvec))
@@ -2308,12 +2322,13 @@ int zone_reclaim(struct zone *zone, gfp_
* @vma: the VMA in which the page is or will be mapped, may be NULL
*
* Test whether page is reclaimable--i.e., should be placed on active/inactive
- * lists vs noreclaim list.
+ * lists vs noreclaim list. The vma argument is !NULL when called from the
+ * fault path to determine how to instantate a new page.
*
* Reasons page might not be reclaimable:
* (1) page's mapping marked non-reclaimable
+ * (2) page is part of an mlocked VMA
*
- * TODO - later patches
*/
int page_reclaimable(struct page *page, struct vm_area_struct *vma)
{
@@ -2323,13 +2338,16 @@ int page_reclaimable(struct page *page,
if (mapping_non_reclaimable(page_mapping(page)))
return 0;

- /* TODO: test page [!]reclaimable conditions */
+#ifdef CONFIG_NORECLAIM_MLOCK
+ if (PageMlocked(page) || (vma && is_mlocked_vma(vma, page)))
+ return 0;
+#endif

return 1;
}

/**
- * check_move_noreclaim_page - check page for reclaimability and move to appropriate zone lru list
+ * check_move_noreclaim_page - check page for reclaimability and move to appropriate lru list
* @page: page to check reclaimability and move to appropriate lru list
* @zone: zone page is in
*
Index: linux-2.6.26-rc2-mm1/include/linux/page-flags.h
===================================================================
--- linux-2.6.26-rc2-mm1.orig/include/linux/page-flags.h 2008-06-06 16:05:15.000000000 -0400
+++ linux-2.6.26-rc2-mm1/include/linux/page-flags.h 2008-06-06 16:06:28.000000000 -0400
@@ -96,6 +96,9 @@ enum pageflags {
PG_swapbacked, /* Page is backed by RAM/swap */
#ifdef CONFIG_NORECLAIM_LRU
PG_noreclaim, /* Page is "non-reclaimable" */
+#ifdef CONFIG_NORECLAIM_MLOCK
+ PG_mlocked, /* Page is vma mlocked */
+#endif
#endif
#ifdef CONFIG_IA64_UNCACHED_ALLOCATOR
PG_uncached, /* Page has been mapped as uncached */
@@ -210,12 +213,25 @@ PAGEFLAG_FALSE(SwapCache)
#ifdef CONFIG_NORECLAIM_LRU
PAGEFLAG(Noreclaim, noreclaim) __CLEARPAGEFLAG(Noreclaim, noreclaim)
TESTCLEARFLAG(Noreclaim, noreclaim)
+
+#ifdef CONFIG_NORECLAIM_MLOCK
+#define MLOCK_PAGES 1
+PAGEFLAG(Mlocked, mlocked) __CLEARPAGEFLAG(Mlocked, mlocked)
+ TESTSCFLAG(Mlocked, mlocked)
+#endif
+
#else
PAGEFLAG_FALSE(Noreclaim) TESTCLEARFLAG_FALSE(Noreclaim)
SETPAGEFLAG_NOOP(Noreclaim) CLEARPAGEFLAG_NOOP(Noreclaim)
__CLEARPAGEFLAG_NOOP(Noreclaim)
#endif

+#if !defined(CONFIG_NORECLAIM_MLOCK)
+#define MLOCK_PAGES 0
+PAGEFLAG_FALSE(Mlocked)
+ SETPAGEFLAG_NOOP(Mlocked) TESTCLEARFLAG_FALSE(Mlocked)
+#endif
+
#ifdef CONFIG_IA64_UNCACHED_ALLOCATOR
PAGEFLAG(Uncached, uncached)
#else
Index: linux-2.6.26-rc2-mm1/include/linux/rmap.h
===================================================================
--- linux-2.6.26-rc2-mm1.orig/include/linux/rmap.h 2008-05-15 11:21:11.000000000 -0400
+++ linux-2.6.26-rc2-mm1/include/linux/rmap.h 2008-06-06 16:06:28.000000000 -0400
@@ -97,6 +97,19 @@ unsigned long page_address_in_vma(struct
*/
int page_mkclean(struct page *);

+#ifdef CONFIG_NORECLAIM_MLOCK
+/*
+ * called in munlock()/munmap() path to check for other vmas holding
+ * the page mlocked.
+ */
+int try_to_unlock(struct page *);
+#else
+static inline int try_to_unlock(struct page *page)
+{
+ return 0; /* a.k.a. SWAP_SUCCESS */
+}
+#endif
+
#else /* !CONFIG_MMU */

#define anon_vma_init() do {} while (0)
@@ -120,5 +133,6 @@ static inline int page_mkclean(struct pa
#define SWAP_SUCCESS 0
#define SWAP_AGAIN 1
#define SWAP_FAIL 2
+#define SWAP_MLOCK 3

#endif /* _LINUX_RMAP_H */
Index: linux-2.6.26-rc2-mm1/mm/rmap.c
===================================================================
--- linux-2.6.26-rc2-mm1.orig/mm/rmap.c 2008-05-15 11:21:11.000000000 -0400
+++ linux-2.6.26-rc2-mm1/mm/rmap.c 2008-06-06 16:06:28.000000000 -0400
@@ -52,6 +52,8 @@

#include <asm/tlbflush.h>

+#include "internal.h"
+
static struct kmem_cache *anon_vma_cachep;

static inline struct anon_vma *anon_vma_alloc(void)
@@ -273,6 +275,32 @@ pte_t *page_check_address(struct page *p
return NULL;
}

+/**
+ * page_mapped_in_vma - check whether a page is really mapped in a VMA
+ * @page: the page to test
+ * @vma: the VMA to test
+ *
+ * Returns 1 if the page is mapped into the page tables of the VMA, 0
+ * if the page is not mapped into the page tables of this VMA. Only
+ * valid for normal file or anonymous VMAs.
+ */
+static int page_mapped_in_vma(struct page *page, struct vm_area_struct *vma)
+{
+ unsigned long address;
+ pte_t *pte;
+ spinlock_t *ptl;
+
+ address = vma_address(page, vma);
+ if (address == -EFAULT) /* out of vma range */
+ return 0;
+ pte = page_check_address(page, vma->vm_mm, address, &ptl);
+ if (!pte) /* the page is not in this mm */
+ return 0;
+ pte_unmap_unlock(pte, ptl);
+
+ return 1;
+}
+
/*
* Subfunctions of page_referenced: page_referenced_one called
* repeatedly from either page_referenced_anon or page_referenced_file.
@@ -294,10 +322,17 @@ static int page_referenced_one(struct pa
if (!pte)
goto out;

+ /*
+ * Don't want to elevate referenced for mlocked page that gets this far,
+ * in order that it progresses to try_to_unmap and is moved to the
+ * noreclaim list.
+ */
if (vma->vm_flags & VM_LOCKED) {
- referenced++;
*mapcount = 1; /* break early from loop */
- } else if (ptep_clear_flush_young(vma, address, pte))
+ goto out_unmap;
+ }
+
+ if (ptep_clear_flush_young(vma, address, pte))
referenced++;

/* Pretend the page is referenced if the task has the
@@ -306,6 +341,7 @@ static int page_referenced_one(struct pa
rwsem_is_locked(&mm->mmap_sem))
referenced++;

+out_unmap:
(*mapcount)--;
pte_unmap_unlock(pte, ptl);
out:
@@ -395,11 +431,6 @@ static int page_referenced_file(struct p
*/
if (mem_cont && !mm_match_cgroup(vma->vm_mm, mem_cont))
continue;
- if ((vma->vm_flags & (VM_LOCKED|VM_MAYSHARE))
- == (VM_LOCKED|VM_MAYSHARE)) {
- referenced++;
- break;
- }
referenced += page_referenced_one(page, vma, &mapcount);
if (!mapcount)
break;
@@ -726,10 +757,15 @@ static int try_to_unmap_one(struct page
* If it's recently referenced (perhaps page_referenced
* skipped over this mm) then we should reactivate it.
*/
- if (!migration && ((vma->vm_flags & VM_LOCKED) ||
- (ptep_clear_flush_young(vma, address, pte)))) {
- ret = SWAP_FAIL;
- goto out_unmap;
+ if (!migration) {
+ if (vma->vm_flags & VM_LOCKED) {
+ ret = SWAP_MLOCK;
+ goto out_unmap;
+ }
+ if (ptep_clear_flush_young(vma, address, pte)) {
+ ret = SWAP_FAIL;
+ goto out_unmap;
+ }
}

/* Nuke the page table entry. */
@@ -811,12 +847,17 @@ out:
* 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 void try_to_unmap_cluster(unsigned long cursor,
- unsigned int *mapcount, struct vm_area_struct *vma)
+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;
pgd_t *pgd;
@@ -828,6 +869,8 @@ static void try_to_unmap_cluster(unsigne
struct page *page;
unsigned long address;
unsigned long end;
+ int ret = SWAP_AGAIN;
+ int locked_vma = 0;

address = (vma->vm_start + cursor) & CLUSTER_MASK;
end = address + CLUSTER_SIZE;
@@ -838,15 +881,26 @@ static void try_to_unmap_cluster(unsigne

pgd = pgd_offset(mm, address);
if (!pgd_present(*pgd))
- return;
+ return ret;

pud = pud_offset(pgd, address);
if (!pud_present(*pud))
- return;
+ return ret;

pmd = pmd_offset(pud, address);
if (!pmd_present(*pmd))
- return;
+ return ret;
+
+ /*
+ * MLOCK_PAGES => feature is configured.
+ * 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 (MLOCK_PAGES && 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);

@@ -859,6 +913,13 @@ static void try_to_unmap_cluster(unsigne
page = vm_normal_page(vma, address, *pte);
BUG_ON(!page || PageAnon(page));

+ if (locked_vma) {
+ mlock_vma_page(page); /* no-op if already mlocked */
+ if (page == check_page)
+ ret = SWAP_MLOCK;
+ continue; /* don't unmap */
+ }
+
if (ptep_clear_flush_young(vma, address, pte))
continue;

@@ -880,39 +941,104 @@ static void try_to_unmap_cluster(unsigne
(*mapcount)--;
}
pte_unmap_unlock(pte - 1, ptl);
+ if (locked_vma)
+ up_read(&vma->vm_mm->mmap_sem);
+ return ret;
}

-static int try_to_unmap_anon(struct page *page, int migration)
+/*
+ * common handling for pages mapped in VM_LOCKED vmas
+ */
+static int try_to_mlock_page(struct page *page, struct vm_area_struct *vma)
+{
+ int mlocked = 0;
+
+ if (down_read_trylock(&vma->vm_mm->mmap_sem)) {
+ if (vma->vm_flags & VM_LOCKED) {
+ mlock_vma_page(page);
+ mlocked++; /* really mlocked the page */
+ }
+ up_read(&vma->vm_mm->mmap_sem);
+ }
+ return mlocked;
+}
+
+/**
+ * try_to_unmap_anon - unmap or unlock anonymous page using the object-based
+ * rmap method
+ * @page: the page to unmap/unlock
+ * @unlock: request for unlock rather than unmap [unlikely]
+ * @migration: unmapping for migration - ignored if @unlock
+ *
+ * Find all the mappings of a page using the mapping pointer and the vma chains
+ * contained in the anon_vma struct it points to.
+ *
+ * This function is only called from try_to_unmap/try_to_unlock for
+ * anonymous pages.
+ * When called from try_to_unlock(), the mmap_sem 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.
+ */
+static int try_to_unmap_anon(struct page *page, int unlock, int migration)
{
struct anon_vma *anon_vma;
struct vm_area_struct *vma;
+ unsigned int mlocked = 0;
int ret = SWAP_AGAIN;

+ if (MLOCK_PAGES && unlikely(unlock))
+ ret = SWAP_SUCCESS; /* default for try_to_unlock() */
+
anon_vma = page_lock_anon_vma(page);
if (!anon_vma)
return ret;

list_for_each_entry(vma, &anon_vma->head, anon_vma_node) {
- ret = try_to_unmap_one(page, vma, migration);
- if (ret == SWAP_FAIL || !page_mapped(page))
- break;
+ if (MLOCK_PAGES && unlikely(unlock)) {
+ if (!((vma->vm_flags & VM_LOCKED) &&
+ page_mapped_in_vma(page, vma)))
+ continue; /* must visit all unlocked vmas */
+ ret = SWAP_MLOCK; /* saw at least one mlocked vma */
+ } else {
+ ret = try_to_unmap_one(page, vma, migration);
+ if (ret == SWAP_FAIL || !page_mapped(page))
+ break;
+ }
+ if (ret == SWAP_MLOCK) {
+ mlocked = try_to_mlock_page(page, vma);
+ if (mlocked)
+ break; /* stop if actually mlocked page */
+ }
}

page_unlock_anon_vma(anon_vma);
+
+ if (mlocked)
+ ret = SWAP_MLOCK; /* actually mlocked the page */
+ else if (ret == SWAP_MLOCK)
+ ret = SWAP_AGAIN; /* saw VM_LOCKED vma */
+
return ret;
}

/**
- * try_to_unmap_file - unmap file page using the object-based rmap method
- * @page: the page to unmap
- * @migration: migration flag
+ * try_to_unmap_file - unmap/unlock file page using the object-based rmap method
+ * @page: the page to unmap/unlock
+ * @unlock: request for unlock rather than unmap [unlikely]
+ * @migration: unmapping for migration - ignored if @unlock
*
* Find all the mappings of a page using the mapping pointer and the vma chains
* contained in the address_space struct it points to.
*
- * This function is only called from try_to_unmap for object-based pages.
+ * This function is only called from try_to_unmap/try_to_unlock for
+ * object-based pages.
+ * When called from try_to_unlock(), the mmap_sem 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.
*/
-static int try_to_unmap_file(struct page *page, int migration)
+static int try_to_unmap_file(struct page *page, int unlock, int migration)
{
struct address_space *mapping = page->mapping;
pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
@@ -923,20 +1049,44 @@ static int try_to_unmap_file(struct page
unsigned long max_nl_cursor = 0;
unsigned long max_nl_size = 0;
unsigned int mapcount;
+ unsigned int mlocked = 0;
+
+ if (MLOCK_PAGES && unlikely(unlock))
+ ret = SWAP_SUCCESS; /* default for try_to_unlock() */

spin_lock(&mapping->i_mmap_lock);
vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) {
- ret = try_to_unmap_one(page, vma, migration);
- if (ret == SWAP_FAIL || !page_mapped(page))
- goto out;
+ if (MLOCK_PAGES && unlikely(unlock)) {
+ if (!(vma->vm_flags & VM_LOCKED))
+ continue; /* must visit all vmas */
+ ret = SWAP_MLOCK;
+ } else {
+ ret = try_to_unmap_one(page, vma, migration);
+ if (ret == SWAP_FAIL || !page_mapped(page))
+ goto out;
+ }
+ if (ret == SWAP_MLOCK) {
+ mlocked = try_to_mlock_page(page, vma);
+ if (mlocked)
+ break; /* stop if actually mlocked page */
+ }
}

+ if (mlocked)
+ goto out;
+
if (list_empty(&mapping->i_mmap_nonlinear))
goto out;

list_for_each_entry(vma, &mapping->i_mmap_nonlinear,
shared.vm_set.list) {
- if ((vma->vm_flags & VM_LOCKED) && !migration)
+ if (MLOCK_PAGES && unlikely(unlock)) {
+ if (!(vma->vm_flags & VM_LOCKED))
+ continue; /* must visit all vmas */
+ ret = SWAP_MLOCK; /* leave mlocked == 0 */
+ goto out; /* no need to look further */
+ }
+ if (!MLOCK_PAGES && !migration && (vma->vm_flags & VM_LOCKED))
continue;
cursor = (unsigned long) vma->vm_private_data;
if (cursor > max_nl_cursor)
@@ -946,7 +1096,7 @@ static int try_to_unmap_file(struct page
max_nl_size = cursor;
}

- if (max_nl_size == 0) { /* any nonlinears locked or reserved */
+ if (max_nl_size == 0) { /* all nonlinears locked or reserved ? */
ret = SWAP_FAIL;
goto out;
}
@@ -970,12 +1120,16 @@ static int try_to_unmap_file(struct page
do {
list_for_each_entry(vma, &mapping->i_mmap_nonlinear,
shared.vm_set.list) {
- if ((vma->vm_flags & VM_LOCKED) && !migration)
+ if (!MLOCK_PAGES && !migration &&
+ (vma->vm_flags & VM_LOCKED))
continue;
cursor = (unsigned long) vma->vm_private_data;
while ( cursor < max_nl_cursor &&
cursor < vma->vm_end - vma->vm_start) {
- try_to_unmap_cluster(cursor, &mapcount, vma);
+ ret = try_to_unmap_cluster(cursor, &mapcount,
+ vma, page);
+ if (ret == SWAP_MLOCK)
+ mlocked = 2; /* to return below */
cursor += CLUSTER_SIZE;
vma->vm_private_data = (void *) cursor;
if ((int)mapcount <= 0)
@@ -996,6 +1150,10 @@ static int try_to_unmap_file(struct page
vma->vm_private_data = NULL;
out:
spin_unlock(&mapping->i_mmap_lock);
+ if (mlocked)
+ ret = SWAP_MLOCK; /* actually mlocked the page */
+ else if (ret == SWAP_MLOCK)
+ ret = SWAP_AGAIN; /* saw VM_LOCKED vma */
return ret;
}

@@ -1011,6 +1169,7 @@ out:
* SWAP_SUCCESS - we succeeded in removing all mappings
* SWAP_AGAIN - we missed a mapping, try again later
* SWAP_FAIL - the page is unswappable
+ * SWAP_MLOCK - page is mlocked.
*/
int try_to_unmap(struct page *page, int migration)
{
@@ -1019,12 +1178,33 @@ int try_to_unmap(struct page *page, int
BUG_ON(!PageLocked(page));

if (PageAnon(page))
- ret = try_to_unmap_anon(page, migration);
+ ret = try_to_unmap_anon(page, 0, migration);
else
- ret = try_to_unmap_file(page, migration);
-
- if (!page_mapped(page))
+ ret = try_to_unmap_file(page, 0, migration);
+ if (ret != SWAP_MLOCK && !page_mapped(page))
ret = SWAP_SUCCESS;
return ret;
}

+#ifdef CONFIG_NORECLAIM_MLOCK
+/**
+ * try_to_unlock - Check page's rmap for other vma's holding page locked.
+ * @page: the page to be unlocked. will be returned with PG_mlocked
+ * cleared if no vmas are VM_LOCKED.
+ *
+ * Return values are:
+ *
+ * SWAP_SUCCESS - no vma's holding page locked.
+ * SWAP_AGAIN - page mapped in mlocked vma -- couldn't acquire mmap sem
+ * SWAP_MLOCK - page is now mlocked.
+ */
+int try_to_unlock(struct page *page)
+{
+ VM_BUG_ON(!PageLocked(page) || PageLRU(page));
+
+ if (PageAnon(page))
+ return try_to_unmap_anon(page, 1, 0);
+ else
+ return try_to_unmap_file(page, 1, 0);
+}
+#endif
Index: linux-2.6.26-rc2-mm1/mm/migrate.c
===================================================================
--- linux-2.6.26-rc2-mm1.orig/mm/migrate.c 2008-06-06 16:05:15.000000000 -0400
+++ linux-2.6.26-rc2-mm1/mm/migrate.c 2008-06-06 16:06:28.000000000 -0400
@@ -359,6 +359,8 @@ static void migrate_page_copy(struct pag
__set_page_dirty_nobuffers(newpage);
}

+ mlock_migrate_page(newpage, page);
+
#ifdef CONFIG_SWAP
ClearPageSwapCache(page);
#endif
Index: linux-2.6.26-rc2-mm1/mm/page_alloc.c
===================================================================
--- linux-2.6.26-rc2-mm1.orig/mm/page_alloc.c 2008-06-06 16:05:57.000000000 -0400
+++ linux-2.6.26-rc2-mm1/mm/page_alloc.c 2008-06-06 16:06:28.000000000 -0400
@@ -258,6 +258,9 @@ static void bad_page(struct page *page)
1 << PG_active |
#ifdef CONFIG_NORECLAIM_LRU
1 << PG_noreclaim |
+#ifdef CONFIG_NORECLAIM_MLOCK
+ 1 << PG_mlocked |
+#endif
#endif
1 << PG_dirty |
1 << PG_reclaim |
@@ -497,6 +500,9 @@ static inline int free_pages_check(struc
#ifdef CONFIG_NORECLAIM_LRU
1 << PG_noreclaim |
#endif
+#ifdef CONFIG_NORECLAIM_MLOCK
+ 1 << PG_mlocked |
+#endif
1 << PG_buddy ))))
bad_page(page);
if (PageDirty(page))
@@ -650,6 +656,9 @@ static int prep_new_page(struct page *pa
1 << PG_active |
#ifdef CONFIG_NORECLAIM_LRU
1 << PG_noreclaim |
+#ifdef CONFIG_NORECLAIM_MLOCK
+ 1 << PG_mlocked |
+#endif
#endif
1 << PG_dirty |
1 << PG_slab |
@@ -669,7 +678,11 @@ static int prep_new_page(struct page *pa

page->flags &= ~(1 << PG_uptodate | 1 << PG_error | 1 << PG_reclaim |
1 << PG_referenced | 1 << PG_arch_1 |
- 1 << PG_owner_priv_1 | 1 << PG_mappedtodisk);
+ 1 << PG_owner_priv_1 | 1 << PG_mappedtodisk
+#ifdef CONFIG_NORECLAIM_MLOCK
+ | 1 << PG_mlocked
+#endif
+ );
set_page_private(page, 0);
set_page_refcounted(page);

Index: linux-2.6.26-rc2-mm1/mm/swap.c
===================================================================
--- linux-2.6.26-rc2-mm1.orig/mm/swap.c 2008-06-06 16:05:15.000000000 -0400
+++ linux-2.6.26-rc2-mm1/mm/swap.c 2008-06-06 16:06:28.000000000 -0400
@@ -307,7 +307,7 @@ void lru_add_drain(void)
put_cpu();
}

-#ifdef CONFIG_NUMA
+#if defined(CONFIG_NUMA) || defined(CONFIG_NORECLAIM_MLOCK)
static void lru_add_drain_per_cpu(struct work_struct *dummy)
{
lru_add_drain();
Index: linux-2.6.26-rc2-mm1/mm/memory.c
===================================================================
--- linux-2.6.26-rc2-mm1.orig/mm/memory.c 2008-05-23 14:21:34.000000000 -0400
+++ linux-2.6.26-rc2-mm1/mm/memory.c 2008-06-06 16:06:28.000000000 -0400
@@ -61,6 +61,8 @@
#include <linux/swapops.h>
#include <linux/elf.h>

+#include "internal.h"
+
#ifndef CONFIG_NEED_MULTIPLE_NODES
/* use the per-pgdat data instead for discontigmem - mbligh */
unsigned long max_mapnr;
@@ -1734,6 +1736,15 @@ gotten:
new_page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, address);
if (!new_page)
goto oom;
+ /*
+ * Don't let another task, with possibly unlocked vma,
+ * keep the mlocked page.
+ */
+ if (vma->vm_flags & VM_LOCKED) {
+ lock_page(old_page); /* for LRU manipulation */
+ clear_page_mlock(old_page);
+ unlock_page(old_page);
+ }
cow_user_page(new_page, old_page, address, vma);
__SetPageUptodate(new_page);

@@ -2176,7 +2187,7 @@ static int do_swap_page(struct mm_struct
page_add_anon_rmap(page, vma, address);

swap_free(entry);
- if (vm_swap_full())
+ if (vm_swap_full() || (vma->vm_flags & VM_LOCKED) || PageMlocked(page))
remove_exclusive_swap_page(page);
unlock_page(page);

@@ -2316,6 +2327,12 @@ static int __do_fault(struct mm_struct *
ret = VM_FAULT_OOM;
goto out;
}
+ /*
+ * Don't let another task, with possibly unlocked vma,
+ * keep the mlocked page.
+ */
+ if (vma->vm_flags & VM_LOCKED)
+ clear_page_mlock(vmf.page);
copy_user_highpage(page, vmf.page, address, vma);
__SetPageUptodate(page);
} else {
Index: linux-2.6.26-rc2-mm1/mm/mmap.c
===================================================================
--- linux-2.6.26-rc2-mm1.orig/mm/mmap.c 2008-05-15 11:20:57.000000000 -0400
+++ linux-2.6.26-rc2-mm1/mm/mmap.c 2008-06-06 16:06:28.000000000 -0400
@@ -652,7 +652,6 @@ again: remove_next = 1 + (end > next->
* If the vma has a ->close operation then the driver probably needs to release
* per-vma resources, so we don't attempt to merge those.
*/
-#define VM_SPECIAL (VM_IO | VM_DONTEXPAND | VM_RESERVED | VM_PFNMAP)

static inline int is_mergeable_vma(struct vm_area_struct *vma,
struct file *file, unsigned long vm_flags)
Index: linux-2.6.26-rc2-mm1/include/linux/mm.h
===================================================================
--- linux-2.6.26-rc2-mm1.orig/include/linux/mm.h 2008-06-06 16:06:24.000000000 -0400
+++ linux-2.6.26-rc2-mm1/include/linux/mm.h 2008-06-06 16:06:28.000000000 -0400
@@ -126,6 +126,11 @@ extern unsigned int kobjsize(const void
#define VM_RandomReadHint(v) ((v)->vm_flags & VM_RAND_READ)

/*
+ * special vmas that are non-mergable, non-mlock()able
+ */
+#define VM_SPECIAL (VM_IO | VM_DONTEXPAND | VM_RESERVED | VM_PFNMAP)
+
+/*
* mapping from the currently active vm_flags protection bits (the
* low four bits) to a page protection mask..
*/
--
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