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Subject[patch 17/19] handle mlocked pages during map/unmap and truncate
V2 -> V3:
+ rebase to 23-mm1 atop RvR's split lru series [no changes]

V1 -> V2:
+ modified mmap.c:mmap_region() to return error if mlock_vma_pages_range()
does. This can only occur if the vma gets removed/changed while
we're switching mmap_sem lock modes. Most callers don't care, but
sys_remap_file_pages() appears to.

Rework of Nick Piggins's "mm: move mlocked pages off the LRU" patch
-- part 2 0f 2.

Remove mlocked pages from the LRU using "NoReclaim infrastructure"
during mmap()/mremap(). Try to move back to normal LRU lists on
munmap() when last locked mapping removed. Removed PageMlocked()
status when page truncated from file.


Originally Signed-off-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Lee Schermerhorn <lee.schermerhorn@hp.com>
Signed-off-by: Rik van Riel <riel@redhat.com>

Index: linux-2.6.24-rc6-mm1/mm/mmap.c
===================================================================
--- linux-2.6.24-rc6-mm1.orig/mm/mmap.c 2007-12-23 23:45:44.000000000 -0500
+++ linux-2.6.24-rc6-mm1/mm/mmap.c 2008-01-02 15:08:07.000000000 -0500
@@ -32,6 +32,8 @@
#include <asm/tlb.h>
#include <asm/mmu_context.h>

+#include "internal.h"
+
#ifndef arch_mmap_check
#define arch_mmap_check(addr, len, flags) (0)
#endif
@@ -1201,9 +1203,13 @@ out:
vm_stat_account(mm, vm_flags, file, len >> PAGE_SHIFT);
if (vm_flags & VM_LOCKED) {
mm->locked_vm += len >> PAGE_SHIFT;
- make_pages_present(addr, addr + len);
- }
- if ((flags & MAP_POPULATE) && !(flags & MAP_NONBLOCK))
+ /*
+ * makes pages present; downgrades, drops, requires mmap_sem
+ */
+ error = mlock_vma_pages_range(vma, addr, addr + len);
+ if (error)
+ return error; /* vma gone! */
+ } else if ((flags & MAP_POPULATE) && !(flags & MAP_NONBLOCK))
make_pages_present(addr, addr + len);
return addr;

@@ -1886,6 +1892,19 @@ int do_munmap(struct mm_struct *mm, unsi
vma = prev? prev->vm_next: mm->mmap;

/*
+ * unlock any mlock()ed ranges before detaching vmas
+ */
+ if (mm->locked_vm) {
+ struct vm_area_struct *tmp = vma;
+ while (tmp && tmp->vm_start < end) {
+ if (tmp->vm_flags & VM_LOCKED)
+ munlock_vma_pages_range(tmp,
+ tmp->vm_start, tmp->vm_end);
+ tmp = tmp->vm_next;
+ }
+ }
+
+ /*
* Remove the vma's, and unmap the actual pages
*/
detach_vmas_to_be_unmapped(mm, vma, prev, end);
@@ -2021,7 +2040,7 @@ out:
mm->total_vm += len >> PAGE_SHIFT;
if (flags & VM_LOCKED) {
mm->locked_vm += len >> PAGE_SHIFT;
- make_pages_present(addr, addr + len);
+ mlock_vma_pages_range(vma, addr, addr + len);
}
return addr;
}
@@ -2032,13 +2051,26 @@ EXPORT_SYMBOL(do_brk);
void exit_mmap(struct mm_struct *mm)
{
struct mmu_gather *tlb;
- struct vm_area_struct *vma = mm->mmap;
+ struct vm_area_struct *vma;
unsigned long nr_accounted = 0;
unsigned long end;

/* mm's last user has gone, and its about to be pulled down */
arch_exit_mmap(mm);

+ if (mm->locked_vm) {
+ vma = mm->mmap;
+ while (vma) {
+ if (vma->vm_flags & VM_LOCKED)
+ munlock_vma_pages_range(vma,
+ vma->vm_start, vma->vm_end);
+ vma = vma->vm_next;
+ }
+ }
+
+ vma = mm->mmap;
+
+
lru_add_drain();
flush_cache_mm(mm);
tlb = tlb_gather_mmu(mm, 1);
Index: linux-2.6.24-rc6-mm1/mm/mremap.c
===================================================================
--- linux-2.6.24-rc6-mm1.orig/mm/mremap.c 2007-12-23 23:45:36.000000000 -0500
+++ linux-2.6.24-rc6-mm1/mm/mremap.c 2008-01-02 15:08:07.000000000 -0500
@@ -23,6 +23,8 @@
#include <asm/cacheflush.h>
#include <asm/tlbflush.h>

+#include "internal.h"
+
static pmd_t *get_old_pmd(struct mm_struct *mm, unsigned long addr)
{
pgd_t *pgd;
@@ -232,8 +234,8 @@ static unsigned long move_vma(struct vm_
if (vm_flags & VM_LOCKED) {
mm->locked_vm += new_len >> PAGE_SHIFT;
if (new_len > old_len)
- make_pages_present(new_addr + old_len,
- new_addr + new_len);
+ mlock_vma_pages_range(vma, new_addr + old_len,
+ new_addr + new_len);
}

return new_addr;
@@ -373,7 +375,7 @@ unsigned long do_mremap(unsigned long ad
vm_stat_account(mm, vma->vm_flags, vma->vm_file, pages);
if (vma->vm_flags & VM_LOCKED) {
mm->locked_vm += pages;
- make_pages_present(addr + old_len,
+ mlock_vma_pages_range(vma, addr + old_len,
addr + new_len);
}
ret = addr;
Index: linux-2.6.24-rc6-mm1/mm/vmscan.c
===================================================================
--- linux-2.6.24-rc6-mm1.orig/mm/vmscan.c 2008-01-02 15:04:11.000000000 -0500
+++ linux-2.6.24-rc6-mm1/mm/vmscan.c 2008-01-02 15:08:07.000000000 -0500
@@ -540,6 +540,10 @@ static unsigned long shrink_page_list(st
goto activate_locked;
case SWAP_AGAIN:
goto keep_locked;
+ case SWAP_MLOCK:
+ ClearPageActive(page);
+ SetPageNoreclaim(page);
+ goto keep_locked; /* to noreclaim list */
case SWAP_SUCCESS:
; /* try to free the page below */
}
Index: linux-2.6.24-rc6-mm1/mm/filemap.c
===================================================================
--- linux-2.6.24-rc6-mm1.orig/mm/filemap.c 2008-01-02 12:37:38.000000000 -0500
+++ linux-2.6.24-rc6-mm1/mm/filemap.c 2008-01-02 15:08:07.000000000 -0500
@@ -2525,8 +2525,16 @@ generic_file_direct_IO(int rw, struct ki
if (rw == WRITE) {
write_len = iov_length(iov, nr_segs);
end = (offset + write_len - 1) >> PAGE_CACHE_SHIFT;
- if (mapping_mapped(mapping))
+ if (mapping_mapped(mapping)) {
+ /*
+ * Calling unmap_mapping_range like this is wrong,
+ * because it can lead to mlocked pages being
+ * discarded (this is true even before the Noreclaim
+ * mlock work). direct-IO vs pagecache is a load of
+ * junk anyway, so who cares.
+ */
unmap_mapping_range(mapping, offset, write_len, 0);
+ }
}

retval = filemap_write_and_wait(mapping);
Index: linux-2.6.24-rc6-mm1/mm/truncate.c
===================================================================
--- linux-2.6.24-rc6-mm1.orig/mm/truncate.c 2007-12-23 23:45:44.000000000 -0500
+++ linux-2.6.24-rc6-mm1/mm/truncate.c 2008-01-02 15:08:07.000000000 -0500
@@ -18,6 +18,7 @@
#include <linux/task_io_accounting_ops.h>
#include <linux/buffer_head.h> /* grr. try_to_release_page,
do_invalidatepage */
+#include "internal.h"


/**
@@ -104,6 +105,7 @@ truncate_complete_page(struct address_sp
cancel_dirty_page(page, PAGE_CACHE_SIZE);

remove_from_page_cache(page);
+ clear_page_mlock(page);
ClearPageUptodate(page);
ClearPageMappedToDisk(page);
page_cache_release(page); /* pagecache ref */
@@ -128,6 +130,7 @@ invalidate_complete_page(struct address_
if (PagePrivate(page) && !try_to_release_page(page, 0))
return 0;

+ clear_page_mlock(page);
ret = remove_mapping(mapping, page);

return ret;
@@ -354,6 +357,7 @@ invalidate_complete_page2(struct address
if (PageDirty(page))
goto failed;

+ clear_page_mlock(page);
BUG_ON(PagePrivate(page));
__remove_from_page_cache(page);
write_unlock_irq(&mapping->tree_lock);
--
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