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Subject[PATCH 2/3] mm/mlock: prepare params outside critical region
Date
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: Michel Lespinasse <walken@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
---
mm/mlock.c | 18 +++++++++++-------
1 file changed, 11 insertions(+), 7 deletions(-)

diff --git a/mm/mlock.c b/mm/mlock.c
index d480cd6..aa7de13 100644
--- a/mm/mlock.c
+++ b/mm/mlock.c
@@ -689,19 +689,21 @@ 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);
@@ -712,11 +714,13 @@ 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;
}

@@ -761,12 +765,12 @@ 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);
--
1.8.1.4


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