[Early draft] Conversion of i_mmap_lock to semaphore

Christoph Lameter
2008-03-04T07:34:37Z

Not there but the system boots and is usable. Complains about atomic
contexts because the tlb functions use a get_cpu() and thus disable preempt.

Not sure yet what to do about the cond_resched_lock stuff etc.

Convert i_mmap_lock to i_mmap_sem

The conversion to a rwsemaphore allows callbacks during rmap traversal
for files in a non atomic context. A rw style lock allows concurrent
walking of the reverse map.

Signed-off-by: Christoph Lameter <clameter@sgi.com>

---
arch/x86/mm/hugetlbpage.c | 4 ++--
fs/hugetlbfs/inode.c | 4 ++--
fs/inode.c | 2 +-
include/linux/fs.h | 2 +-
include/linux/mm.h | 2 +-
kernel/fork.c | 4 ++--
mm/filemap.c | 8 ++++----
mm/filemap_xip.c | 4 ++--
mm/fremap.c | 4 ++--
mm/hugetlb.c | 11 +++++------
mm/memory.c | 28 ++++++++--------------------
mm/migrate.c | 4 ++--
mm/mmap.c | 16 ++++++++--------
mm/mremap.c | 4 ++--
mm/rmap.c | 20 +++++++++-----------
15 files changed, 51 insertions(+), 66 deletions(-)

Index: linux-2.6/arch/x86/mm/hugetlbpage.c
===================================================================
--- linux-2.6.orig/arch/x86/mm/hugetlbpage.c 2008-03-03 22:59:25.386848427 -0800
+++ linux-2.6/arch/x86/mm/hugetlbpage.c 2008-03-03 22:59:31.174878038 -0800
@@ -69,7 +69,7 @@ static void huge_pmd_share(struct mm_str
if (!vma_shareable(vma, addr))
return;

- spin_lock(&mapping->i_mmap_lock);
+ down_read(&mapping->i_mmap_sem);
vma_prio_tree_foreach(svma, &iter, &mapping->i_mmap, idx, idx) {
if (svma == vma)
continue;
@@ -94,7 +94,7 @@ static void huge_pmd_share(struct mm_str
put_page(virt_to_page(spte));
spin_unlock(&mm->page_table_lock);
out:
- spin_unlock(&mapping->i_mmap_lock);
+ up_read(&mapping->i_mmap_sem);
}

/*
Index: linux-2.6/fs/hugetlbfs/inode.c
===================================================================
--- linux-2.6.orig/fs/hugetlbfs/inode.c 2008-03-03 22:59:25.410848010 -0800
+++ linux-2.6/fs/hugetlbfs/inode.c 2008-03-03 22:59:31.174878038 -0800
@@ -454,10 +454,10 @@ static int hugetlb_vmtruncate(struct ino
pgoff = offset >> PAGE_SHIFT;

i_size_write(inode, offset);
- spin_lock(&mapping->i_mmap_lock);
+ down_read(&mapping->i_mmap_sem);
if (!prio_tree_empty(&mapping->i_mmap))
hugetlb_vmtruncate_list(&mapping->i_mmap, pgoff);
- spin_unlock(&mapping->i_mmap_lock);
+ up_read(&mapping->i_mmap_sem);
truncate_hugepages(inode, offset);
return 0;
}
Index: linux-2.6/fs/inode.c
===================================================================
--- linux-2.6.orig/fs/inode.c 2008-03-03 22:59:25.418848099 -0800
+++ linux-2.6/fs/inode.c 2008-03-03 22:59:31.202878206 -0800
@@ -210,7 +210,7 @@ void inode_init_once(struct inode *inode
INIT_LIST_HEAD(&inode->i_devices);
INIT_RADIX_TREE(&inode->i_data.page_tree, GFP_ATOMIC);
rwlock_init(&inode->i_data.tree_lock);
- spin_lock_init(&inode->i_data.i_mmap_lock);
+ init_rwsem(&inode->i_data.i_mmap_sem);
INIT_LIST_HEAD(&inode->i_data.private_list);
spin_lock_init(&inode->i_data.private_lock);
INIT_RAW_PRIO_TREE_ROOT(&inode->i_data.i_mmap);
Index: linux-2.6/include/linux/fs.h
===================================================================
--- linux-2.6.orig/include/linux/fs.h 2008-03-03 22:59:25.430848089 -0800
+++ linux-2.6/include/linux/fs.h 2008-03-03 22:59:31.202878206 -0800
@@ -503,7 +503,7 @@ struct address_space {
unsigned int i_mmap_writable;/* count VM_SHARED mappings */
struct prio_tree_root i_mmap; /* tree of private and shared mappings */
struct list_head i_mmap_nonlinear;/*list VM_NONLINEAR mappings */
- spinlock_t i_mmap_lock; /* protect tree, count, list */
+ struct rw_semaphore i_mmap_sem; /* protect tree, count, list */
unsigned int truncate_count; /* Cover race condition with truncate */
unsigned long nrpages; /* number of total pages */
pgoff_t writeback_index;/* writeback starts here */
Index: linux-2.6/include/linux/mm.h
===================================================================
--- linux-2.6.orig/include/linux/mm.h 2008-03-03 22:59:25.442848167 -0800
+++ linux-2.6/include/linux/mm.h 2008-03-03 22:59:31.202878206 -0800
@@ -709,7 +709,7 @@ struct zap_details {
struct address_space *check_mapping; /* Check page->mapping if set */
pgoff_t first_index; /* Lowest page->index to unmap */
pgoff_t last_index; /* Highest page->index to unmap */
- spinlock_t *i_mmap_lock; /* For unmap_mapping_range: */
+ struct rw_semaphore *i_mmap_sem; /* For unmap_mapping_range: */
unsigned long truncate_count; /* Compare vm_truncate_count */
};

Index: linux-2.6/kernel/fork.c
===================================================================
--- linux-2.6.orig/kernel/fork.c 2008-03-03 22:59:27.230858013 -0800
+++ linux-2.6/kernel/fork.c 2008-03-03 22:59:31.202878206 -0800
@@ -273,12 +273,12 @@ static int dup_mmap(struct mm_struct *mm
atomic_dec(&inode->i_writecount);

/* insert tmp into the share list, just after mpnt */
- spin_lock(&file->f_mapping->i_mmap_lock);
+ down_write(&file->f_mapping->i_mmap_sem);
tmp->vm_truncate_count = mpnt->vm_truncate_count;
flush_dcache_mmap_lock(file->f_mapping);
vma_prio_tree_add(tmp, mpnt);
flush_dcache_mmap_unlock(file->f_mapping);
- spin_unlock(&file->f_mapping->i_mmap_lock);
+ up_write(&file->f_mapping->i_mmap_sem);
}

/*
Index: linux-2.6/mm/filemap.c
===================================================================
--- linux-2.6.orig/mm/filemap.c 2008-03-03 22:59:25.462848256 -0800
+++ linux-2.6/mm/filemap.c 2008-03-03 22:59:31.206878010 -0800
@@ -62,16 +62,16 @@ generic_file_direct_IO(int rw, struct ki
/*
* Lock ordering:
*
- * ->i_mmap_lock (vmtruncate)
+ * ->i_mmap_sem (vmtruncate)
* ->private_lock (__free_pte->__set_page_dirty_buffers)
* ->swap_lock (exclusive_swap_page, others)
* ->mapping->tree_lock
*
* ->i_mutex
- * ->i_mmap_lock (truncate->unmap_mapping_range)
+ * ->i_mmap_sem (truncate->unmap_mapping_range)
*
* ->mmap_sem
- * ->i_mmap_lock
+ * ->i_mmap_sem
* ->page_table_lock or pte_lock (various, mainly in memory.c)
* ->mapping->tree_lock (arch-dependent flush_dcache_mmap_lock)
*
@@ -88,7 +88,7 @@ generic_file_direct_IO(int rw, struct ki
* ->sb_lock (fs/fs-writeback.c)
* ->mapping->tree_lock (__sync_single_inode)
*
- * ->i_mmap_lock
+ * ->i_mmap_sem
* ->anon_vma.lock (vma_adjust)
*
* ->anon_vma.lock
Index: linux-2.6/mm/filemap_xip.c
===================================================================
--- linux-2.6.orig/mm/filemap_xip.c 2008-03-03 22:59:25.474848348 -0800
+++ linux-2.6/mm/filemap_xip.c 2008-03-03 22:59:31.206878010 -0800
@@ -184,7 +184,7 @@ __xip_unmap (struct address_space * mapp
if (!page)
return;

- spin_lock(&mapping->i_mmap_lock);
+ down_read(&mapping->i_mmap_sem);
vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) {
mm = vma->vm_mm;
address = vma->vm_start +
@@ -207,7 +207,7 @@ __xip_unmap (struct address_space * mapp
emm_notify(mm, emm_invalidate_end,
address, address + PAGE_SIZE);
}
- spin_unlock(&mapping->i_mmap_lock);
+ up_read(&mapping->i_mmap_sem);
}

/*
Index: linux-2.6/mm/fremap.c
===================================================================
--- linux-2.6.orig/mm/fremap.c 2008-03-03 22:59:25.482848555 -0800
+++ linux-2.6/mm/fremap.c 2008-03-03 22:59:31.206878010 -0800
@@ -205,13 +205,13 @@ asmlinkage long sys_remap_file_pages(uns
}
goto out;
}
- spin_lock(&mapping->i_mmap_lock);
+ down_write(&mapping->i_mmap_sem);
flush_dcache_mmap_lock(mapping);
vma->vm_flags |= VM_NONLINEAR;
vma_prio_tree_remove(vma, &mapping->i_mmap);
vma_nonlinear_insert(vma, &mapping->i_mmap_nonlinear);
flush_dcache_mmap_unlock(mapping);
- spin_unlock(&mapping->i_mmap_lock);
+ up_write(&mapping->i_mmap_sem);
}

emm_notify(mm, emm_invalidate_start, start, end);
Index: linux-2.6/mm/hugetlb.c
===================================================================
--- linux-2.6.orig/mm/hugetlb.c 2008-03-03 22:59:27.230858013 -0800
+++ linux-2.6/mm/hugetlb.c 2008-03-03 22:59:31.206878010 -0800
@@ -746,7 +746,7 @@ void __unmap_hugepage_range(struct vm_ar
struct page *page;
struct page *tmp;
/*
- * A page gathering list, protected by per file i_mmap_lock. The
+ * A page gathering list, protected by per file i_mmap_sem. The
* lock is used to avoid list corruption from multiple unmapping
* of the same page since we are using page->lru.
*/
@@ -756,7 +756,6 @@ void __unmap_hugepage_range(struct vm_ar
BUG_ON(start & ~HPAGE_MASK);
BUG_ON(end & ~HPAGE_MASK);

- /* i_mmap_lock held */
emm_notify(mm, emm_invalidate_start, start, end);
spin_lock(&mm->page_table_lock);
for (address = start; address < end; address += HPAGE_SIZE) {
@@ -797,9 +796,9 @@ void unmap_hugepage_range(struct vm_area
* do nothing in this case.
*/
if (vma->vm_file) {
- spin_lock(&vma->vm_file->f_mapping->i_mmap_lock);
+ down_write(&vma->vm_file->f_mapping->i_mmap_sem);
__unmap_hugepage_range(vma, start, end);
- spin_unlock(&vma->vm_file->f_mapping->i_mmap_lock);
+ up_write(&vma->vm_file->f_mapping->i_mmap_sem);
}
}

@@ -1042,7 +1041,7 @@ void hugetlb_change_protection(struct vm
BUG_ON(address >= end);
flush_cache_range(vma, address, end);

- spin_lock(&vma->vm_file->f_mapping->i_mmap_lock);
+ down_read(&vma->vm_file->f_mapping->i_mmap_sem);
spin_lock(&mm->page_table_lock);
for (; address < end; address += HPAGE_SIZE) {
ptep = huge_pte_offset(mm, address);
@@ -1057,7 +1056,7 @@ void hugetlb_change_protection(struct vm
}
}
spin_unlock(&mm->page_table_lock);
- spin_unlock(&vma->vm_file->f_mapping->i_mmap_lock);
+ up_read(&vma->vm_file->f_mapping->i_mmap_sem);

flush_tlb_range(vma, start, end);
}
Index: linux-2.6/mm/memory.c
===================================================================
--- linux-2.6.orig/mm/memory.c 2008-03-03 22:59:25.502849006 -0800
+++ linux-2.6/mm/memory.c 2008-03-03 22:59:31.206878010 -0800
@@ -830,7 +830,6 @@ unsigned long unmap_vmas(struct mmu_gath
unsigned long tlb_start = 0; /* For tlb_finish_mmu */
int tlb_start_valid = 0;
unsigned long start = start_addr;
- spinlock_t *i_mmap_lock = details? details->i_mmap_lock: NULL;
int fullmm = (*tlbp)->fullmm;

for ( ; vma && vma->vm_start < end_addr; vma = vma->vm_next) {
@@ -868,21 +867,11 @@ unsigned long unmap_vmas(struct mmu_gath

tlb_finish_mmu(*tlbp, tlb_start, start);

- if (need_resched() ||
- (i_mmap_lock && spin_needbreak(i_mmap_lock))) {
- if (i_mmap_lock) {
- *tlbp = NULL;
- goto out;
- }
- cond_resched();
- }
-
*tlbp = tlb_gather_mmu(vma->vm_mm, fullmm);
tlb_start_valid = 0;
zap_work = ZAP_BLOCK_SIZE;
}
}
-out:
return start; /* which is now the end (or restart) address */
}

@@ -905,7 +894,6 @@ unsigned long zap_page_range(struct vm_a
tlb = tlb_gather_mmu(mm, 0);
update_hiwater_rss(mm);

- /* i_mmap_lock may be held */
emm_notify(mm, emm_invalidate_start, address, end);
end = unmap_vmas(&tlb, vma, address, end, &nr_accounted, details);
emm_notify(mm, emm_invalidate_end, address, end);
@@ -1749,7 +1737,7 @@ unwritable_page:
/*
* Helper functions for unmap_mapping_range().
*
- * __ Notes on dropping i_mmap_lock to reduce latency while unmapping __
+ * __ Notes on dropping i_mmap_sem to reduce latency while unmapping __
*
* We have to restart searching the prio_tree whenever we drop the lock,
* since the iterator is only valid while the lock is held, and anyway
@@ -1768,7 +1756,7 @@ unwritable_page:
* can't efficiently keep all vmas in step with mapping->truncate_count:
* so instead reset them all whenever it wraps back to 0 (then go to 1).
* mapping->truncate_count and vma->vm_truncate_count are protected by
- * i_mmap_lock.
+ * i_mmap_sem.
*
* In order to make forward progress despite repeatedly restarting some
* large vma, note the restart_addr from unmap_vmas when it breaks out:
@@ -1818,7 +1806,7 @@ again:

restart_addr = zap_page_range(vma, start_addr,
end_addr - start_addr, details);
- need_break = need_resched() || spin_needbreak(details->i_mmap_lock);
+ need_break = need_resched();

if (restart_addr >= end_addr) {
/* We have now completed this vma: mark it so */
@@ -1832,9 +1820,9 @@ again:
goto again;
}

- spin_unlock(details->i_mmap_lock);
+ up_write(details->i_mmap_sem);
cond_resched();
- spin_lock(details->i_mmap_lock);
+ down_write(details->i_mmap_sem);
return -EINTR;
}

@@ -1928,9 +1916,9 @@ void unmap_mapping_range(struct address_
details.last_index = hba + hlen - 1;
if (details.last_index < details.first_index)
details.last_index = ULONG_MAX;
- details.i_mmap_lock = &mapping->i_mmap_lock;
+ details.i_mmap_sem = &mapping->i_mmap_sem;

- spin_lock(&mapping->i_mmap_lock);
+ down_write(&mapping->i_mmap_sem);

/* Protect against endless unmapping loops */
mapping->truncate_count++;
@@ -1945,7 +1933,7 @@ void unmap_mapping_range(struct address_
unmap_mapping_range_tree(&mapping->i_mmap, &details);
if (unlikely(!list_empty(&mapping->i_mmap_nonlinear)))
unmap_mapping_range_list(&mapping->i_mmap_nonlinear, &details);
- spin_unlock(&mapping->i_mmap_lock);
+ up_write(&mapping->i_mmap_sem);
}
EXPORT_SYMBOL(unmap_mapping_range);

Index: linux-2.6/mm/migrate.c
===================================================================
--- linux-2.6.orig/mm/migrate.c 2008-03-03 22:59:25.510849324 -0800
+++ linux-2.6/mm/migrate.c 2008-03-03 22:59:31.206878010 -0800
@@ -202,12 +202,12 @@ static void remove_file_migration_ptes(s
if (!mapping)
return;

- spin_lock(&mapping->i_mmap_lock);
+ down_read(&mapping->i_mmap_sem);

vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff)
remove_migration_pte(vma, old, new);

- spin_unlock(&mapping->i_mmap_lock);
+ up_read(&mapping->i_mmap_sem);
}

/*
Index: linux-2.6/mm/mmap.c
===================================================================
--- linux-2.6.orig/mm/mmap.c 2008-03-03 22:59:25.522848812 -0800
+++ linux-2.6/mm/mmap.c 2008-03-03 22:59:31.210878368 -0800
@@ -186,7 +186,7 @@ error:
}

/*
- * Requires inode->i_mapping->i_mmap_lock
+ * Requires inode->i_mapping->i_mmap_sem
*/
static void __remove_shared_vm_struct(struct vm_area_struct *vma,
struct file *file, struct address_space *mapping)
@@ -214,9 +214,9 @@ void unlink_file_vma(struct vm_area_stru

if (file) {
struct address_space *mapping = file->f_mapping;
- spin_lock(&mapping->i_mmap_lock);
+ down_write(&mapping->i_mmap_sem);
__remove_shared_vm_struct(vma, file, mapping);
- spin_unlock(&mapping->i_mmap_lock);
+ up_write(&mapping->i_mmap_sem);
}
}

@@ -439,7 +439,7 @@ static void vma_link(struct mm_struct *m
mapping = vma->vm_file->f_mapping;

if (mapping) {
- spin_lock(&mapping->i_mmap_lock);
+ down_write(&mapping->i_mmap_sem);
vma->vm_truncate_count = mapping->truncate_count;
}
anon_vma_lock(vma);
@@ -449,7 +449,7 @@ static void vma_link(struct mm_struct *m

anon_vma_unlock(vma);
if (mapping)
- spin_unlock(&mapping->i_mmap_lock);
+ up_write(&mapping->i_mmap_sem);

mm->map_count++;
validate_mm(mm);
@@ -536,7 +536,7 @@ again: remove_next = 1 + (end > next->
mapping = file->f_mapping;
if (!(vma->vm_flags & VM_NONLINEAR))
root = &mapping->i_mmap;
- spin_lock(&mapping->i_mmap_lock);
+ down_write(&mapping->i_mmap_sem);
if (importer &&
vma->vm_truncate_count != next->vm_truncate_count) {
/*
@@ -620,7 +620,7 @@ again: remove_next = 1 + (end > next->
if (anon_vma)
spin_unlock(&anon_vma->lock);
if (mapping)
- spin_unlock(&mapping->i_mmap_lock);
+ up_write(&mapping->i_mmap_sem);

if (remove_next) {
if (file)
@@ -2064,7 +2064,7 @@ void exit_mmap(struct mm_struct *mm)

/* Insert vm structure into process list sorted by address
* and into the inode's i_mmap tree. If vm_file is non-NULL
- * then i_mmap_lock is taken here.
+ * then i_mmap_sem is taken here.
*/
int insert_vm_struct(struct mm_struct * mm, struct vm_area_struct * vma)
{
Index: linux-2.6/mm/mremap.c
===================================================================
--- linux-2.6.orig/mm/mremap.c 2008-03-03 22:59:25.530848880 -0800
+++ linux-2.6/mm/mremap.c 2008-03-03 22:59:31.210878368 -0800
@@ -86,7 +86,7 @@ static void move_ptes(struct vm_area_str
* and we propagate stale pages into the dst afterward.
*/
mapping = vma->vm_file->f_mapping;
- spin_lock(&mapping->i_mmap_lock);
+ down_write(&mapping->i_mmap_sem);
if (new_vma->vm_truncate_count &&
new_vma->vm_truncate_count != vma->vm_truncate_count)
new_vma->vm_truncate_count = 0;
@@ -119,7 +119,7 @@ static void move_ptes(struct vm_area_str
pte_unmap_nested(new_pte - 1);
pte_unmap_unlock(old_pte - 1, old_ptl);
if (mapping)
- spin_unlock(&mapping->i_mmap_lock);
+ up_write(&mapping->i_mmap_sem);
emm_notify(mm, emm_invalidate_end, old_start, old_end);
}

Index: linux-2.6/mm/rmap.c
===================================================================
--- linux-2.6.orig/mm/rmap.c 2008-03-03 22:59:25.542848702 -0800
+++ linux-2.6/mm/rmap.c 2008-03-03 22:59:31.210878368 -0800
@@ -24,7 +24,7 @@
* inode->i_alloc_sem (vmtruncate_range)
* mm->mmap_sem
* page->flags PG_locked (lock_page)
- * mapping->i_mmap_lock
+ * mapping->i_mmap_sem
* anon_vma->lock
* mm->page_table_lock or pte_lock
* zone->lru_lock (in mark_page_accessed, isolate_lru_page)
@@ -368,14 +368,14 @@ static int page_referenced_file(struct p
* The page lock not only makes sure that page->mapping cannot
* suddenly be NULLified by truncation, it makes sure that the
* structure at mapping cannot be freed and reused yet,
- * so we can safely take mapping->i_mmap_lock.
+ * so we can safely take mapping->i_mmap_sem.
*/
BUG_ON(!PageLocked(page));

- spin_lock(&mapping->i_mmap_lock);
+ down_read(&mapping->i_mmap_sem);

/*
- * i_mmap_lock does not stabilize mapcount at all, but mapcount
+ * i_mmap_sem does not stabilize mapcount at all, but mapcount
* is more likely to be accurate if we note it after spinning.
*/
mapcount = page_mapcount(page);
@@ -398,7 +398,7 @@ static int page_referenced_file(struct p
break;
}

- spin_unlock(&mapping->i_mmap_lock);
+ up_read(&mapping->i_mmap_sem);
return referenced;
}

@@ -482,12 +482,12 @@ static int page_mkclean_file(struct addr

BUG_ON(PageAnon(page));

- spin_lock(&mapping->i_mmap_lock);
+ down_read(&mapping->i_mmap_sem);
vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) {
if (vma->vm_flags & VM_SHARED)
ret += page_mkclean_one(page, vma);
}
- spin_unlock(&mapping->i_mmap_lock);
+ up_read(&mapping->i_mmap_sem);
return ret;
}

@@ -923,7 +923,7 @@ static int try_to_unmap_file(struct page
unsigned long max_nl_size = 0;
unsigned int mapcount;

- spin_lock(&mapping->i_mmap_lock);
+ down_read(&mapping->i_mmap_sem);
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))
@@ -960,7 +960,6 @@ static int try_to_unmap_file(struct page
mapcount = page_mapcount(page);
if (!mapcount)
goto out;
- cond_resched_lock(&mapping->i_mmap_lock);

max_nl_size = (max_nl_size + CLUSTER_SIZE - 1) & CLUSTER_MASK;
if (max_nl_cursor == 0)
@@ -982,7 +981,6 @@ static int try_to_unmap_file(struct page
}
vma->vm_private_data = (void *) max_nl_cursor;
}
- cond_resched_lock(&mapping->i_mmap_lock);
max_nl_cursor += CLUSTER_SIZE;
} while (max_nl_cursor <= max_nl_size);

@@ -994,7 +992,7 @@ static int try_to_unmap_file(struct page
list_for_each_entry(vma, &mapping->i_mmap_nonlinear, shared.vm_set.list)
vma->vm_private_data = NULL;
out:
- spin_unlock(&mapping->i_mmap_lock);
+ up_write(&mapping->i_mmap_sem);
return ret;
}