mm/mlock: prepare params outside critical region

All mlock related syscalls prepare lock limits, lengths and start
parameters with the mmap_sem held.  Move this logic outside of the
critical region.  For the case of mlock, continue incrementing the
amount already locked by mm->locked_vm with the rwsem taken.

Signed-off-by: Davidlohr Bueso <davidlohr@hp.com>
Cc: Rik van Riel <riel@redhat.com>
Reviewed-by: Michel Lespinasse <walken@google.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/mlock.c b/mm/mlock.c
index 192e6ee..10819ed 100644 (file)
--- a/mm/mlock.c
+++ b/mm/mlock.c
@@ -709,19 +709,21 @@ SYSCALL_DEFINE2(mlock, unsigned long, start, size_t, len)
 
        lru_add_drain_all();    /* flush pagevec */
 
-       down_write(&current->mm->mmap_sem);
        len = PAGE_ALIGN(len + (start & ~PAGE_MASK));
        start &= PAGE_MASK;
 
-       locked = len >> PAGE_SHIFT;
-       locked += current->mm->locked_vm;
-
        lock_limit = rlimit(RLIMIT_MEMLOCK);
        lock_limit >>= PAGE_SHIFT;
+       locked = len >> PAGE_SHIFT;
+
+       down_write(&current->mm->mmap_sem);
+
+       locked += current->mm->locked_vm;
 
        /* check against resource limits */
        if ((locked <= lock_limit) || capable(CAP_IPC_LOCK))
                error = do_mlock(start, len, 1);
+
        up_write(&current->mm->mmap_sem);
        if (!error)
                error = __mm_populate(start, len, 0);
@@ -732,11 +734,13 @@ SYSCALL_DEFINE2(munlock, unsigned long, start, size_t, len)
 {
        int ret;
 
-       down_write(&current->mm->mmap_sem);
        len = PAGE_ALIGN(len + (start & ~PAGE_MASK));
        start &= PAGE_MASK;
+
+       down_write(&current->mm->mmap_sem);
        ret = do_mlock(start, len, 0);
        up_write(&current->mm->mmap_sem);
+
        return ret;
 }
 
@@ -781,12 +785,12 @@ SYSCALL_DEFINE1(mlockall, int, flags)
        if (flags & MCL_CURRENT)
                lru_add_drain_all();    /* flush pagevec */
 
-       down_write(&current->mm->mmap_sem);
-
        lock_limit = rlimit(RLIMIT_MEMLOCK);
        lock_limit >>= PAGE_SHIFT;
 
        ret = -ENOMEM;
+       down_write(&current->mm->mmap_sem);
+
        if (!(flags & MCL_CURRENT) || (current->mm->total_vm <= lock_limit) ||
            capable(CAP_IPC_LOCK))
                ret = do_mlockall(flags);