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Subject[PATCH 6/6] kvm/book3s: drop mmap_sem now that locked_vm is atomic
Date
With locked_vm now an atomic, there is no need to take mmap_sem as
writer. Delete and refactor accordingly.

Signed-off-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Cc: Alexey Kardashevskiy <aik@ozlabs.ru>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Christoph Lameter <cl@linux.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Paul Mackerras <paulus@ozlabs.org>
Cc: <linux-mm@kvack.org>
Cc: <kvm-ppc@vger.kernel.org>
Cc: <linuxppc-dev@lists.ozlabs.org>
Cc: <linux-kernel@vger.kernel.org>
---
arch/powerpc/kvm/book3s_64_vio.c | 34 +++++++++++---------------------
1 file changed, 12 insertions(+), 22 deletions(-)

diff --git a/arch/powerpc/kvm/book3s_64_vio.c b/arch/powerpc/kvm/book3s_64_vio.c
index e7fdb6d10eeb..8e034c3a5d25 100644
--- a/arch/powerpc/kvm/book3s_64_vio.c
+++ b/arch/powerpc/kvm/book3s_64_vio.c
@@ -56,7 +56,7 @@ static unsigned long kvmppc_stt_pages(unsigned long tce_pages)
return tce_pages + ALIGN(stt_bytes, PAGE_SIZE) / PAGE_SIZE;
}

-static long kvmppc_account_memlimit(unsigned long stt_pages, bool inc)
+static long kvmppc_account_memlimit(unsigned long pages, bool inc)
{
long ret = 0;
s64 locked_vm;
@@ -64,33 +64,23 @@ static long kvmppc_account_memlimit(unsigned long stt_pages, bool inc)
if (!current || !current->mm)
return ret; /* process exited */

- down_write(&current->mm->mmap_sem);
-
- locked_vm = atomic64_read(&current->mm->locked_vm);
if (inc) {
- unsigned long locked, lock_limit;
+ unsigned long lock_limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;

- locked = locked_vm + stt_pages;
- lock_limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;
- if (locked > lock_limit && !capable(CAP_IPC_LOCK))
+ locked_vm = atomic64_add_return(pages, &current->mm->locked_vm);
+ if (locked_vm > lock_limit && !capable(CAP_IPC_LOCK)) {
ret = -ENOMEM;
- else
- atomic64_add(stt_pages, &current->mm->locked_vm);
+ atomic64_sub(pages, &current->mm->locked_vm);
+ }
} else {
- if (WARN_ON_ONCE(stt_pages > locked_vm))
- stt_pages = locked_vm;
-
- atomic64_sub(stt_pages, &current->mm->locked_vm);
+ locked_vm = atomic64_sub_return(pages, &current->mm->locked_vm);
+ WARN_ON_ONCE(locked_vm < 0);
}

- pr_debug("[%d] RLIMIT_MEMLOCK KVM %c%ld %ld/%ld%s\n", current->pid,
- inc ? '+' : '-',
- stt_pages << PAGE_SHIFT,
- atomic64_read(&current->mm->locked_vm) << PAGE_SHIFT,
- rlimit(RLIMIT_MEMLOCK),
- ret ? " - exceeded" : "");
-
- up_write(&current->mm->mmap_sem);
+ pr_debug("[%d] RLIMIT_MEMLOCK KVM %c%lu %lld/%lu%s\n", current->pid,
+ inc ? '+' : '-', pages << PAGE_SHIFT,
+ locked_vm << PAGE_SHIFT,
+ rlimit(RLIMIT_MEMLOCK), ret ? " - exceeded" : "");

return ret;
}
--
2.21.0
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