diff options
Diffstat (limited to 'mm/madvise.c')
| -rw-r--r-- | mm/madvise.c | 51 |
1 files changed, 44 insertions, 7 deletions
diff --git a/mm/madvise.c b/mm/madvise.c index 4e196155a0c..e75096b5a6d 100644 --- a/mm/madvise.c +++ b/mm/madvise.c @@ -12,6 +12,24 @@ #include <linux/hugetlb.h> /* + * Any behaviour which results in changes to the vma->vm_flags needs to + * take mmap_sem for writing. Others, which simply traverse vmas, need + * to only take it for reading. + */ +static int madvise_need_mmap_write(int behavior) +{ + switch (behavior) { + case MADV_REMOVE: + case MADV_WILLNEED: + case MADV_DONTNEED: + return 0; + default: + /* be safe, default to 1. list exceptions explicitly */ + return 1; + } +} + +/* * We can potentially split a vm area into separate * areas, each area with its own behavior. */ @@ -155,10 +173,14 @@ static long madvise_dontneed(struct vm_area_struct * vma, * Other filesystems return -ENOSYS. */ static long madvise_remove(struct vm_area_struct *vma, + struct vm_area_struct **prev, unsigned long start, unsigned long end) { struct address_space *mapping; - loff_t offset, endoff; + loff_t offset, endoff; + int error; + + *prev = NULL; /* tell sys_madvise we drop mmap_sem */ if (vma->vm_flags & (VM_LOCKED|VM_NONLINEAR|VM_HUGETLB)) return -EINVAL; @@ -177,7 +199,12 @@ static long madvise_remove(struct vm_area_struct *vma, + ((loff_t)vma->vm_pgoff << PAGE_SHIFT); endoff = (loff_t)(end - vma->vm_start - 1) + ((loff_t)vma->vm_pgoff << PAGE_SHIFT); - return vmtruncate_range(mapping->host, offset, endoff); + + /* vmtruncate_range needs to take i_mutex and i_alloc_sem */ + up_read(¤t->mm->mmap_sem); + error = vmtruncate_range(mapping->host, offset, endoff); + down_read(¤t->mm->mmap_sem); + return error; } static long @@ -199,7 +226,7 @@ madvise_vma(struct vm_area_struct *vma, struct vm_area_struct **prev, error = madvise_behavior(vma, prev, start, end, behavior); break; case MADV_REMOVE: - error = madvise_remove(vma, start, end); + error = madvise_remove(vma, prev, start, end); break; case MADV_WILLNEED: @@ -261,7 +288,10 @@ asmlinkage long sys_madvise(unsigned long start, size_t len_in, int behavior) int error = -EINVAL; size_t len; - down_write(¤t->mm->mmap_sem); + if (madvise_need_mmap_write(behavior)) + down_write(¤t->mm->mmap_sem); + else + down_read(¤t->mm->mmap_sem); if (start & ~PAGE_MASK) goto out; @@ -312,14 +342,21 @@ asmlinkage long sys_madvise(unsigned long start, size_t len_in, int behavior) if (error) goto out; start = tmp; - if (start < prev->vm_end) + if (prev && start < prev->vm_end) start = prev->vm_end; error = unmapped_error; if (start >= end) goto out; - vma = prev->vm_next; + if (prev) + vma = prev->vm_next; + else /* madvise_remove dropped mmap_sem */ + vma = find_vma(current->mm, start); } out: - up_write(¤t->mm->mmap_sem); + if (madvise_need_mmap_write(behavior)) + up_write(¤t->mm->mmap_sem); + else + up_read(¤t->mm->mmap_sem); + return error; } |