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Subject[PATCH 10 of 12] Convert mm_lock to use semaphores after i_mmap_lock and anon_vma_lock
Date
From
# HG changeset patch
# User Andrea Arcangeli <andrea@qumranet.com>
# Date 1208872187 -7200
# Node ID f8210c45f1c6f8b38d15e5dfebbc5f7c1f890c93
# Parent bdb3d928a0ba91cdce2b61bd40a2f80bddbe4ff2
Convert mm_lock to use semaphores after i_mmap_lock and anon_vma_lock
conversion.

Signed-off-by: Andrea Arcangeli <andrea@qumranet.com>

diff --git a/include/linux/mm.h b/include/linux/mm.h
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1062,10 +1062,10 @@
* mm_lock and mm_unlock are expensive operations that may take a long time.
*/
struct mm_lock_data {
- spinlock_t **i_mmap_locks;
- spinlock_t **anon_vma_locks;
- size_t nr_i_mmap_locks;
- size_t nr_anon_vma_locks;
+ struct rw_semaphore **i_mmap_sems;
+ struct rw_semaphore **anon_vma_sems;
+ size_t nr_i_mmap_sems;
+ size_t nr_anon_vma_sems;
};
extern int mm_lock(struct mm_struct *mm, struct mm_lock_data *data);
extern void mm_unlock(struct mm_struct *mm, struct mm_lock_data *data);
diff --git a/mm/mmap.c b/mm/mmap.c
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -2243,8 +2243,8 @@
static int mm_lock_cmp(const void *a, const void *b)
{
cond_resched();
- if ((unsigned long)*(spinlock_t **)a <
- (unsigned long)*(spinlock_t **)b)
+ if ((unsigned long)*(struct rw_semaphore **)a <
+ (unsigned long)*(struct rw_semaphore **)b)
return -1;
else if (a == b)
return 0;
@@ -2252,7 +2252,7 @@
return 1;
}

-static unsigned long mm_lock_sort(struct mm_struct *mm, spinlock_t **locks,
+static unsigned long mm_lock_sort(struct mm_struct *mm, struct rw_semaphore **sems,
int anon)
{
struct vm_area_struct *vma;
@@ -2261,59 +2261,59 @@
for (vma = mm->mmap; vma; vma = vma->vm_next) {
if (anon) {
if (vma->anon_vma)
- locks[i++] = &vma->anon_vma->lock;
+ sems[i++] = &vma->anon_vma->sem;
} else {
if (vma->vm_file && vma->vm_file->f_mapping)
- locks[i++] = &vma->vm_file->f_mapping->i_mmap_lock;
+ sems[i++] = &vma->vm_file->f_mapping->i_mmap_sem;
}
}

if (!i)
goto out;

- sort(locks, i, sizeof(spinlock_t *), mm_lock_cmp, NULL);
+ sort(sems, i, sizeof(struct rw_semaphore *), mm_lock_cmp, NULL);

out:
return i;
}

static inline unsigned long mm_lock_sort_anon_vma(struct mm_struct *mm,
- spinlock_t **locks)
+ struct rw_semaphore **sems)
{
- return mm_lock_sort(mm, locks, 1);
+ return mm_lock_sort(mm, sems, 1);
}

static inline unsigned long mm_lock_sort_i_mmap(struct mm_struct *mm,
- spinlock_t **locks)
+ struct rw_semaphore **sems)
{
- return mm_lock_sort(mm, locks, 0);
+ return mm_lock_sort(mm, sems, 0);
}

-static void mm_lock_unlock(spinlock_t **locks, size_t nr, int lock)
+static void mm_lock_unlock(struct rw_semaphore **sems, size_t nr, int lock)
{
- spinlock_t *last = NULL;
+ struct rw_semaphore *last = NULL;
size_t i;

for (i = 0; i < nr; i++)
/* Multiple vmas may use the same lock. */
- if (locks[i] != last) {
- BUG_ON((unsigned long) last > (unsigned long) locks[i]);
- last = locks[i];
+ if (sems[i] != last) {
+ BUG_ON((unsigned long) last > (unsigned long) sems[i]);
+ last = sems[i];
if (lock)
- spin_lock(last);
+ down_write(last);
else
- spin_unlock(last);
+ up_write(last);
}
}

-static inline void __mm_lock(spinlock_t **locks, size_t nr)
+static inline void __mm_lock(struct rw_semaphore **sems, size_t nr)
{
- mm_lock_unlock(locks, nr, 1);
+ mm_lock_unlock(sems, nr, 1);
}

-static inline void __mm_unlock(spinlock_t **locks, size_t nr)
+static inline void __mm_unlock(struct rw_semaphore **sems, size_t nr)
{
- mm_lock_unlock(locks, nr, 0);
+ mm_lock_unlock(sems, nr, 0);
}

/*
@@ -2325,57 +2325,57 @@
*/
int mm_lock(struct mm_struct *mm, struct mm_lock_data *data)
{
- spinlock_t **anon_vma_locks, **i_mmap_locks;
+ struct rw_semaphore **anon_vma_sems, **i_mmap_sems;

down_write(&mm->mmap_sem);
if (mm->map_count) {
- anon_vma_locks = vmalloc(sizeof(spinlock_t *) * mm->map_count);
- if (unlikely(!anon_vma_locks)) {
+ anon_vma_sems = vmalloc(sizeof(struct rw_semaphore *) * mm->map_count);
+ if (unlikely(!anon_vma_sems)) {
up_write(&mm->mmap_sem);
return -ENOMEM;
}

- i_mmap_locks = vmalloc(sizeof(spinlock_t *) * mm->map_count);
- if (unlikely(!i_mmap_locks)) {
+ i_mmap_sems = vmalloc(sizeof(struct rw_semaphore *) * mm->map_count);
+ if (unlikely(!i_mmap_sems)) {
up_write(&mm->mmap_sem);
- vfree(anon_vma_locks);
+ vfree(anon_vma_sems);
return -ENOMEM;
}

- data->nr_anon_vma_locks = mm_lock_sort_anon_vma(mm, anon_vma_locks);
- data->nr_i_mmap_locks = mm_lock_sort_i_mmap(mm, i_mmap_locks);
+ data->nr_anon_vma_sems = mm_lock_sort_anon_vma(mm, anon_vma_sems);
+ data->nr_i_mmap_sems = mm_lock_sort_i_mmap(mm, i_mmap_sems);

- if (data->nr_anon_vma_locks) {
- __mm_lock(anon_vma_locks, data->nr_anon_vma_locks);
- data->anon_vma_locks = anon_vma_locks;
+ if (data->nr_anon_vma_sems) {
+ __mm_lock(anon_vma_sems, data->nr_anon_vma_sems);
+ data->anon_vma_sems = anon_vma_sems;
} else
- vfree(anon_vma_locks);
+ vfree(anon_vma_sems);

- if (data->nr_i_mmap_locks) {
- __mm_lock(i_mmap_locks, data->nr_i_mmap_locks);
- data->i_mmap_locks = i_mmap_locks;
+ if (data->nr_i_mmap_sems) {
+ __mm_lock(i_mmap_sems, data->nr_i_mmap_sems);
+ data->i_mmap_sems = i_mmap_sems;
} else
- vfree(i_mmap_locks);
+ vfree(i_mmap_sems);
}
return 0;
}

-static void mm_unlock_vfree(spinlock_t **locks, size_t nr)
+static void mm_unlock_vfree(struct rw_semaphore **sems, size_t nr)
{
- __mm_unlock(locks, nr);
- vfree(locks);
+ __mm_unlock(sems, nr);
+ vfree(sems);
}

/* avoid memory allocations for mm_unlock to prevent deadlock */
void mm_unlock(struct mm_struct *mm, struct mm_lock_data *data)
{
if (mm->map_count) {
- if (data->nr_anon_vma_locks)
- mm_unlock_vfree(data->anon_vma_locks,
- data->nr_anon_vma_locks);
- if (data->i_mmap_locks)
- mm_unlock_vfree(data->i_mmap_locks,
- data->nr_i_mmap_locks);
+ if (data->nr_anon_vma_sems)
+ mm_unlock_vfree(data->anon_vma_sems,
+ data->nr_anon_vma_sems);
+ if (data->i_mmap_sems)
+ mm_unlock_vfree(data->i_mmap_sems,
+ data->nr_i_mmap_sems);
}
up_write(&mm->mmap_sem);
}

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