diff options
| author | Nick Piggin <npiggin@suse.de> | 2007-05-06 14:49:53 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@woody.linux-foundation.org> | 2007-05-07 12:12:54 -0700 |
| commit | 0a27a14a62921b438bb6f33772690d345a089be6 (patch) | |
| tree | 3a0a23880832ded1160b60a93300f4248a7de91f /mm | |
| parent | b4169525bc2336ea6581c6ff2aa88b2671e3b9f9 (diff) | |
| download | lwn-0a27a14a62921b438bb6f33772690d345a089be6.tar.gz lwn-0a27a14a62921b438bb6f33772690d345a089be6.zip | |
mm: madvise avoid exclusive mmap_sem
Avoid down_write of the mmap_sem in madvise when we can help it.
Acked-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Nick Piggin <npiggin@suse.de>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
| -rw-r--r-- | mm/madvise.c | 33 |
1 files changed, 29 insertions, 4 deletions
diff --git a/mm/madvise.c b/mm/madvise.c index 603c5257ed6e..e75096b5a6d3 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. */ @@ -183,9 +201,9 @@ static long madvise_remove(struct vm_area_struct *vma, + ((loff_t)vma->vm_pgoff << PAGE_SHIFT); /* vmtruncate_range needs to take i_mutex and i_alloc_sem */ - up_write(¤t->mm->mmap_sem); + up_read(¤t->mm->mmap_sem); error = vmtruncate_range(mapping->host, offset, endoff); - down_write(¤t->mm->mmap_sem); + down_read(¤t->mm->mmap_sem); return error; } @@ -270,7 +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; @@ -332,6 +353,10 @@ asmlinkage long sys_madvise(unsigned long start, size_t len_in, int behavior) 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; } |